JP4076769B2 - Light emitting device and electric appliance - Google Patents

Description

[0001]
[Field of the Invention]
The present invention relates to a light emitting device using an organic light emitting element having an anode, a cathode, and a film containing an organic compound that can emit light by applying an electric field (hereinafter referred to as “organic compound layer”). In particular, the present invention relates to a light-emitting device using an organic light-emitting element having a lower driving voltage and a longer element lifetime than conventional ones. Note that the light emitting device in this specification refers to an image display device or a light emitting device using an organic light emitting element as a light emitting element. In addition, connectors with organic light-emitting elements such as anisotropic conductive film (FPC: Flexible Printed Circuit) or TAB (Tape Automated Bonding) tape or TCP (Tape Carrier Package) attached, printed on the end of TAB tape or TCP It is assumed that the light emitting device includes all modules provided with a wiring board or modules in which an IC (integrated circuit) is directly mounted on an organic light emitting element by a COG (Chip On Glass) method.
[0002]
[Prior art]
An organic light emitting element is an element that emits light when an electric field is applied. The light emission mechanism is an excited state in which an electron injected from the cathode and a hole injected from the anode are recombined at the emission center in the organic compound layer by applying a voltage across the organic compound layer between the electrodes. It is said that this molecule emits light by releasing energy when the molecular exciton returns to the ground state (hereinafter referred to as “molecular exciton”).
[0003]
Note that the type of molecular exciton formed by the organic compound can be a singlet excited state or a triplet excited state. However, in this specification, both excited states contribute to light emission. .
[0004]
In such an organic light emitting device, the organic compound layer is usually formed as a thin film having a thickness of less than 1 μm. Further, since the organic light emitting element is a self-luminous element in which the organic compound layer itself emits light, a backlight as used in a conventional liquid crystal display is not necessary. Therefore, it is a great advantage that the organic light emitting device can be manufactured to be extremely thin and light.
[0005]
Also, for example, in an organic compound layer of about 100 to 200 nm, the time from carrier injection to recombination is about several tens of nanoseconds considering the carrier mobility of the organic compound layer. Even if the process from light emission to light emission is included, light emission occurs in the order of microseconds or less. Therefore, one of the features is that the response speed is very fast.
[0006]
Furthermore, since the organic light emitting element is a carrier injection type light emitting element, it can be driven with a direct current voltage, and noise hardly occurs. Regarding the driving voltage, the thickness of the organic compound layer is first made to be a uniform ultra-thin film of about 100 nm, and electrode materials that reduce the carrier injection barrier for the organic compound layer are selected. ) 100cd / m at 5.5V ² (Reference 1: CW Tang and SA Van Slyke, “Organic electroluminescent diodes”, Applied Physics Letters, vol. 51, No. 12, 913-915 (1987)).
[0007]
Due to these thin, lightweight, high-speed response, and direct current low voltage driving characteristics, organic light-emitting devices are attracting attention as next-generation flat panel display devices. Further, since it is a self-luminous type and has a wide viewing angle, the visibility is relatively good, and it is considered effective as an element used for a display screen of a portable device.
[0008]
By the way, with the configuration of the organic light emitting device shown in Document 1, first, as a method for reducing the carrier injection barrier with respect to the organic compound layer, an Mg: Ag alloy having a low work function and relatively stable is used for the cathode. , Enhances the electron injection property. This makes it possible to inject a large amount of carriers into the organic compound layer.
[0009]
Furthermore, as an organic compound layer, a hole transport layer made of a diamine compound and tris (8-quinolinolato) aluminum (abbreviation: Alq _Three The recombination efficiency of carriers is drastically improved by applying a single heterostructure in which an electron-transporting light-emitting layer composed of This is explained as follows.
[0010]
For example, Alq _Three In the case of organic light-emitting devices with only a single layer, Alq _Three Therefore, most of the electrons injected from the cathode reach the anode without recombining with holes, and the efficiency of light emission is extremely poor. That is, a material that can transport both electrons and holes in a balanced manner (hereinafter referred to as “bipolar material”) is used in order to efficiently emit light (or drive at a low voltage) in a single layer organic light emitting device. Need, Alq _Three Does not meet that requirement.
[0011]
However, if a single heterostructure as in Document 1 is applied, electrons injected from the cathode are blocked at the interface between the hole transport layer and the electron transporting light emitting layer and confined in the electron transporting light emitting layer. Therefore, carrier recombination is efficiently performed in the electron-transporting light-emitting layer, leading to efficient light emission.
[0012]
If the concept of such a carrier blocking function is developed, it becomes possible to control the carrier recombination region. As an example, by inserting a layer capable of blocking holes (hole blocking layer) between the hole transport layer and the electron transport layer, the holes are confined in the hole transport layer, and There is a report that succeeded in making one emit light. (Reference 2: Yasunori KIJIMA, Nobutoshi ASAI and Shin-ichiro TAMURA, “A Blue Organic Light Emitting Diode”, Japanese Journal of Applied Physics, Vol. 38, 5274-5277 (1999)).
[0013]
In addition, the organic light-emitting device in Document 1 can be said to be an idea of functional separation in which hole transport is performed by a hole transport layer, and electron transport and light emission are performed by an electron transport light-emitting layer. This concept of functional separation has further evolved into a double heterostructure (three-layer structure) in which a light emitting layer is sandwiched between a hole transport layer and an electron transport layer (Reference 3: Chihaya ADACHI, Shizuo TOKITO, Tetsuo). TSUTSUI and Shogo SAITO, "Electroluminescence in Organic Films with Three-Layered Structure", Japanese Journal of Applied Physics, Vol. 27, No. 2, L269-L271 (1988)).
[0014]
The advantage of such functional separation is that it is no longer necessary to have various functions (such as light-emitting properties, carrier transportability, and carrier injection properties from electrodes) at the same time due to the functional separation. Etc. (for example, it becomes unnecessary to search for a bipolar material forcibly). That is, a high light emission efficiency can be easily achieved by combining materials having good light emission characteristics and materials having excellent carrier transportability.
[0015]
Because of these advantages, the concept of the laminated structure (carrier blocking function or function separation) itself described in Document 1 has been widely used up to now.
[0016]
[Problems to be solved by the invention]
However, since the laminated structure as described above is a junction between different kinds of substances (especially between insulators), an energy barrier always occurs at the interface. If an energy barrier exists, the movement of carriers at the interface is hindered, which raises the following two problems.
[0017]
The first is that it becomes an obstacle to further reducing the drive voltage. In fact, in the current organic light-emitting device, the driving voltage is superior to the device with a single layer structure using a conjugated polymer, and the top data in power efficiency (unit: [lm / W]) (however, singlet) (Reference 4: Tetsuo Tsutsui, Journal of the Japan Society of Applied Physics, Organic Molecules and Bioelectronics, Vol. 11, No. 1, P. 8) (2000)).
[0018]
Note that the conjugated polymer described in Document 4 is a bipolar material, and the carrier recombination efficiency can achieve a level equivalent to that of the laminated structure. Therefore, if the recombination efficiency of carriers can be made equal without using a laminated structure, such as by using a bipolar material, a single layer structure with fewer interfaces actually shows a lower drive voltage. Yes.
[0019]
This means that the movement of carriers is hindered at the interface between layers in the organic compound layer (for example, between the hole transport layer and the light emitting layer, hereinafter referred to as “organic interface”), and higher driving is achieved. Explain that the voltage is needed.
[0020]
For example, at the interface between the electrode and the organic compound layer, there is a method in which a material that relaxes the energy barrier is inserted to increase the carrier injection property and reduce the driving voltage (Reference 5: Takeo Wakimoto, Yoshinori Fukuda, Kenichi). Nagayama, Akira Yokoi, Hitoshi Nakada, and Masami Tsuchida, "Organic EL Cells Using Alkaline Metal Compounds as Electron Injection Materials", IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 44, NO. 8, 1245-1248 (1997)). In Reference 5, Li as an electron injection layer ₂ By using O, the drive voltage has been successfully reduced.
[0021]
However, the carrier mobility at the organic interface is still an unsolved field, and is considered to be an important point for catching up with a low driving voltage of a single layer structure using a bipolar material.
[0022]
Furthermore, as another problem caused by the energy barrier, the influence on the device lifetime of the organic light emitting device can be considered. That is, the movement of carriers is hindered and the brightness is reduced due to the accumulation of charges.
[0023]
Although no clear theory has been established regarding this degradation mechanism, the luminance can be reduced by inserting a hole injection layer between the anode and the hole transport layer, and using rectangular wave ac drive instead of dc drive. (Ref. 6: SA VanSlyke, CH Chen, and CW Tang, "Organic electroluminescent devices with improved stability", Applied Physics Letters, Vol. 69, No. 15, 2160-2162 (1996) )). This can be said to be experimental support that the reduction in luminance could be suppressed by eliminating charge accumulation by inserting the hole injection layer and ac driving.
[0024]
From the above, the laminated structure can easily increase the recombination efficiency of carriers and has a merit that the selection range of materials can be widened from the viewpoint of functional separation, while at the same time, by creating many organic interfaces (especially It can be said that by blocking the carriers and creating an organic interface for recombining the carriers, the movement of the carriers is hindered and the drive voltage and luminance are reduced.
[0025]
Therefore, in the present invention, while utilizing the advantages (functional separation) of the conventionally used laminated structure, the mobility of carriers is improved by relaxing the energy barrier present in the organic compound layer, and the driving voltage is higher than in the past. Another object is to provide an organic light-emitting element that is low and has a long lifetime.
[0026]
In particular, it is different from the conventionally used stacked structure in which carriers are blocked in the light emitting layer to recombine the carriers, and by creating an element with a different concept, the organic interface existing in the organic compound layer is eliminated and the carrier is removed. It is an object of the present invention to improve the mobility of the material and to exhibit the functions of various materials (hereinafter referred to as “functional expression”) as well as the functional separation of the laminated structure. Accordingly, an object of the present invention is to provide an organic light emitting device having a lower driving voltage and a longer device life than the conventional one.
[0027]
Furthermore, it is an object of the present invention to provide a light-emitting device that uses such an organic light-emitting element and has a driving voltage lower than that of a conventional device and has a long lifetime. Furthermore, it is an object of the present invention to provide an electric appliance that uses the light-emitting device to produce an electric appliance that has lower power consumption than the conventional one and that can be maintained for a long time.
[0028]
[Means for Solving the Problems]
Regarding the relaxation of the energy barrier in the laminated structure, it is noticeable in the technique of inserting the carrier injection layer as shown in Document 5. An explanation using an energy band diagram is shown in FIG. 1 by taking the hole injection layer as an example.
[0029]
In FIG. 1A, the anode 101 and the hole transport layer 102 are directly joined, but in this case, the energy barrier 104 between the anode 101 and the hole transport layer 102 is large. However, the HOMO level located between the ionization potential of the anode (in the case of metal, which is synonymous with the work function) and the highest occupied molecular orbital (hereinafter referred to as “HOMO”) level of the hole transport layer. By inserting the material having the hole injection layer 103, the energy barrier can be designed stepwise (FIG. 1 (b)).
[0030]
By designing a step-like energy barrier as shown in FIG. 1B, the carrier injection property from the electrode can be improved, and the drive voltage can be lowered to some extent. However, the problem is that by increasing the number of layers, the number of organic interfaces increases conversely. This is considered to be the reason why the single layer structure holds the top data of the driving voltage and power efficiency as shown in Document 4.
[0031]
In other words, by overcoming this point, while taking advantage of the laminated structure (a variety of materials can be combined and no complicated molecular design is required), the driving voltage and power efficiency of the single layer structure can be achieved. I can catch up.
[0032]
The fundamental concept is that the energy barrier in the organic compound layer can be relaxed and the movement of carriers can be prevented without increasing the number of organic interfaces. The inventor has devised an element structure capable of realizing this concept by the following method.
[0033]
First of all, it is a technique to relax the energy barrier for holes, but it is a layer that mixes a hole injection material with a high HOMO level (low ionization potential) and a hole transport material with high hole mobility (hereinafter, (Referred to as “hole transporting mixed layer”). With this technique, the hole injection material receives holes from the anode side, and the hole transport material plays a role in the hole transporting mixed layer. The two-layer function of a hole transport layer can be realized in a single layer.
[0034]
Further, it is preferable to form a concentration gradient in the hole transporting mixed layer described above. That is, as shown in FIG. 2, the proportion of the hole injection material is large on the side close to the anode, and the proportion of the hole transport material is increased as the distance from the anode is increased. By forming such a concentration gradient, the process from the reception to the transport of holes from the anode side to the transport is performed without forming a large energy barrier, which contributes to a reduction in driving voltage and a longer life.
[0035]
Note that the concentration gradient in FIG. 2 is illustrated using a straight line for the sake of convenience, but it is not necessarily a straight line, and it is sufficient that an increasing or decreasing gradient is formed. In fact, when controlling, it is considered that there are many cases where it becomes a curve. The same applies to other concentration gradients described in this specification.
[0036]
Next, there is a method to reduce the energy barrier against electrons. An electron injection material with a low level of the lowest unoccupied molecular orbital (hereinafter referred to as “LUMO”) (high electron affinity) and electron transport with high electron mobility. A layer mixed with a material (hereinafter referred to as an “electron transporting mixed layer”) may be provided. With this method, the electron injection material plays the role of receiving electrons from the cathode side, and the electron transport material plays the role of transporting electrons in the electron transporting mixed layer. It is possible to realize the functions in one layer.
[0037]
Moreover, it is preferable to form a concentration gradient in the electron transporting mixed layer described above. That is, as shown in FIG. 3, the ratio close to the cathode has a large proportion of the electron injecting material, and the proportion of the electron transporting material increases as the distance from the cathode increases. By forming such a concentration gradient, the process from the reception of electrons from the cathode side to the transport is carried out without lubrication, thereby contributing to a decrease in driving voltage and a longer life.
[0038]
In addition, there is a method of relaxing the energy barrier in the light emitting layer. That is, a layer that is made bipolar by mixing a hole transport material having a high hole mobility and an electron transport material having a high electron mobility (hereinafter referred to as a “bipolar mixed layer”) is used as a light emitting layer. What is necessary is just to provide. In this case, although the carrier blocking function at the interface between both ends of the light emitting layer is reduced, the carrier mobility difference between the electron transport layer and the bipolar mixed layer and the carrier mobility difference between the hole transport layer and the bipolar mixed layer Tends to recombine in a bipolar mixed layer.
[0039]
Further, it is preferable to form a concentration gradient in the bipolar mixed layer described above. That is, as shown in FIG. 4, the ratio of the hole transport material is large on the side close to the anode, and the ratio of the electron transport material is increased as the distance from the cathode is approached. By forming such a concentration gradient, from the transport of holes and electrons to recombination, lubrication is performed without forming a large energy barrier, which contributes to lower drive voltage and longer life. .
[0040]
In the bipolar mixed layer, it is considered that a material having lower excitation energy emits light. The excitation energy in this specification refers to the energy difference between HOMO and LUMO. Regarding HOMO, it can be measured by photoelectron spectroscopy and may be considered synonymous with ionization potential. Also, LUMO can be calculated from the excitation energy and the value of the HOMO level by defining the excitation energy as the end of the absorption spectrum for convenience.
[0041]
Further, there is a method of emitting light by doping a light emitting material into the bipolar mixed layer described above. In this case, the light emitting material which is a dopant needs to have lower excitation energy than the hole transport material and the electron transport material included in the bipolar mixed layer. In particular, it is preferable to use a carrier trap type dopant (eg, rubrene) because the carrier recombination efficiency is further increased.
[0042]
Moreover, although the hole blocking layer was shown in the literature 2, such a layer is generally comprised with a blocking material. The blocking material is generally a material having an excitation energy larger than that of the light emitting layer material (that is, diffusion of molecular excitons can be prevented) and a carrier can also be blocked. In many cases, it mainly blocks holes.
[0043]
The inventor has also devised a method for forming a layer (hereinafter referred to as a “blocking mixed layer”) in which a blocking material and a material of a light emitting layer (or a host material of the light emitting layer) are mixed. In this case, the blocking mixed layer can also function as a light emitting layer, and can also be regarded as a light emitting layer capable of efficiently blocking carriers and molecular excitons inside the layer.
[0044]
Regarding the blocking mixed layer, it is particularly preferable to form a concentration gradient. This is because, by gradually increasing the concentration of the blocking material as the distance from the light emitting layer increases, it is possible to lubricate the movement of non-blocking carriers (electrons in the case of hole blocking materials).
[0045]
In recent years, organic light-emitting devices that can convert the energy released when returning from the triplet excited state to the ground state (hereinafter referred to as “triplet excited energy”) into light emission have been announced one after another, and have high emission efficiency. (Reference 7: DF O'Brien, MA Baldo, ME Thompson and SR Forrest, "Improved energy transfer in electrophosphorescent devices", Applied Physics Letters, vol. 74, No. 3, 442-444 (1999) (Reference 8: Tetsuo TSUTSUI, Moon-Jae YANG, Masayuki YAHIRO, Kenji NAKAMURA, Teruichi WATANABE, Taishi TSUJI, Yoshinori FUKUDA, Takeo WAKIMOTO and Satoshi MIYAGUCHI, "High Quantum Efficiency in Organic Light-Emitting Devices with Iridium-Complex as a Triplet Emissive Center ", Japanese Journal of Applied Physics, Vol. 38, L1502-L1504 (1999)).
[0046]
Document 7 uses a metal complex having platinum as the central metal, and Document 8 uses a metal complex having iridium as the central metal. Organic light-emitting elements that can convert these triplet excitation energy into light emission (hereinafter referred to as “triplet light-emitting elements”) can achieve higher luminance emission and higher emission efficiency than conventional ones.
[0047]
However, according to the report example of Reference 8, the initial luminance is 500 cd / m. ² When set to, the luminance half-life is about 170 hours, which causes a problem in the element lifetime. Therefore, by applying the present invention to a triplet light-emitting element, it is possible to realize a very high-performance light-emitting element in which the lifetime of the element is long in addition to high luminance light emission and high light emission efficiency by light emission from a triplet excited state. .
[0048]
Therefore, as described above, the concept of the present invention that reduces the number of interfaces (or relaxes the energy barrier) and lubricates carrier movement by using a carrier transport layer or a light emitting layer as a mixed layer. Those applied to triplet light-emitting elements are also included in the present invention.
[0049]
By the way, as a model in which the movement of carriers is hindered by the formation of the organic interface, the present inventor considers the following two mechanisms.
[0050]
One possible mechanism is one that arises from the morphology of the organic interface. The organic compound layer in the organic light emitting device is usually an amorphous film, which is formed by aggregation of molecules of the organic compound by an intermolecular force mainly including dipole interaction. However, when a heterostructure (laminated structure) is formed by using such an aggregate of molecules, a difference in the size and shape of the molecule may greatly affect the interface (that is, the organic interface) of the heterostructure.
[0051]
In particular, when a heterostructure is formed using materials having greatly different molecular sizes, it is considered that the matching of the junction at the organic interface is deteriorated. The conceptual diagram is shown in FIG. In FIG. 21, a first layer 2111 composed of small molecules 2101 and a second layer 2112 composed of large molecules 2102 are stacked. In this case, an inconsistent region 2114 occurs at the organic interface 2113 to be formed.
[0052]
The region 2114 having poor matching shown in FIG. 21 may become a barrier (or energy barrier) that hinders the movement of carriers, and thus it is suggested that the region 2114 becomes an obstacle to further reducing the driving voltage. In addition, carriers that cannot exceed the energy barrier accumulate as charges, which may induce a decrease in luminance as described above.
[0053]
Another possible mechanism is that resulting from the step of forming a laminated structure (ie, forming an organic interface). In order to avoid contamination when forming each layer, the organic light emitting device having a laminated structure usually uses a multi-chamber type (in-line type) vapor deposition apparatus as shown in FIG. 22 from the viewpoint of carrier blocking and functional separation. To make.
[0054]
The example shown in FIG. 22 is a conceptual diagram of a vapor deposition apparatus for forming a three-layer structure (double heterostructure) of a hole transport layer, a light emitting layer, and an electron transport layer. First, a substrate having an anode (indium tin oxide (hereinafter referred to as “ITO”)) is carried into the carry-in chamber, and the surface of the anode is cleaned by irradiating ultraviolet rays in a vacuum atmosphere in the ultraviolet irradiation chamber. . In particular, when the anode is an oxide such as ITO, an oxidation treatment is performed in the pretreatment chamber. Furthermore, in order to form each layer of the laminated structure, a hole transport layer is formed in the vapor deposition chamber 2201, a light emitting layer (three colors of red, green, and blue in FIG. 22) is formed in the vapor deposition chambers 2202 to 2204, and an electron is formed in the vapor deposition chamber 2205. A transport layer is formed, and a cathode is deposited in a deposition chamber 2206. Finally, sealing is performed in the sealing chamber, and the organic light emitting device is obtained by taking out from the carry-out chamber.
[0055]
A feature of such an in-line type vapor deposition apparatus is that vapor deposition of each layer is performed in different vapor deposition chambers 2201 to 2205. That is, the device configuration is such that the material of each layer hardly mixes with each other.
[0056]
However, the inside of the vapor deposition apparatus is usually 10 ^-Four -10 ^-Five Although the pressure is reduced to about Pascal, there are trace amounts of gaseous components (oxygen, water, etc.). In the case of such a degree of vacuum, it is said that an adsorption layer of a monomolecular layer is easily formed even in a few seconds even with such a trace amount of gas components.
[0057]
Therefore, when an organic light emitting device having a laminated structure is manufactured using an apparatus as shown in FIG. 22, there is a problem that a large interval is generated between the layers. That is, there is a concern that an adsorption layer (hereinafter referred to as an “impurity layer”) with a very small amount of a gas component may be formed during an interval between formation of each layer, particularly when transporting via the second transport chamber. is there.
[0058]
The conceptual diagram is shown in FIG. FIG. 23 shows a trace amount of impurities 2303 (water or oxygen) between the first layer 2311 made of the first organic compound 2301 and the second layer 2312 made of the second organic compound 2302. Etc.) is formed.
[0059]
The impurity layer formed between the respective layers (that is, the organic interface) in this manner becomes an impurity region for trapping carriers after completion of the organic light emitting device, and prevents the carrier from moving. End up. Furthermore, if there is an impurity region that traps carriers, charges accumulate therein, which may induce a reduction in luminance as described above.
[0060]
Considering such a mechanism, in order to overcome the problems that occur at the organic interface as described above (deterioration of the morphology of the organic interface and formation of impurity layers), both the device structure and the fabrication process are the conventional laminated structure. It is necessary to remove from the element. For example, as an example of an organic light emitting device in which the organic interface is completely eliminated, only a single layer (hereinafter referred to as “mixed single layer”) in which a hole transport material and an electron transport material are mixed is provided between both electrodes. There is a report of the organic light-emitting device provided (Reference 9: Shigeki NAKA, Kazuhisa SHINNO, Hiroyuki OKADA, Hiroshi ONNAGAWA and Kazuo MIYASHITA, "Organic Electroluminescent Devices Using a Mixed Single Layer", Japanese Journal of Applied Physics, Vol. 33, No 12B, L1772-L1774 (1994)).
[0061]
In Reference 9, 4,4′-bis [N- (3-methylphenyl) -N-phenyl-amino] -biphenyl (hereinafter referred to as “TPD”) that has hole transportability and electron transportability. Alq _Three Are mixed in a ratio of 1: 4 to form a single layer structure. However, the laminated structure (ie TPD and Alq _Three When compared with a heterostructure that forms an organic interface made of, it is shown that the emission efficiency is inferior to that of a laminated structure.
[0062]
The reason is considered that in the case of a mixed single layer, holes injected from the anode and electrons injected from the cathode often escape to the counter electrode without recombination. Since the laminated structure has a carrier blocking function, such a problem does not occur.
[0063]
This can be rephrased as the cause of the absence of function in the mixed monolayer of Document 9. That is, in the organic compound layer, a region close to the anode shows a function of hole transport, a region close to the cathode shows a function of electron transport, and a light emitting region (that is, a region where carriers recombine in a part away from both electrodes). If a region that can express each function is not provided, even if the organic interface is eliminated, efficient light emission cannot be achieved. In addition, since the entire organic compound layer functions as a light emitting layer, there is a possibility that carrier recombination may actually be performed near the electrode, and the energy may be transferred to the electrode material to be quenched.
[0064]
In view of the fact that the mixed monolayer cannot exhibit sufficient performance in this way, the present inventor particularly eliminates the organic interface when forming the bipolar mixed layer in FIG. In contrast to this, we have devised a method to realize an organic light-emitting device capable of functioning. The conceptual diagram is shown in FIG.
[0065]
In FIG. 24, in an organic compound layer 2403 composed of two types of a hole transport material and an electron transport material, a hole transport region 2405 composed of a hole transport material, an electron transport region 2406 composed of an electron transport material, and a hole transport material And a mixed region 2407 in which the electron transport material is mixed. Although the anode 2402 is provided over the substrate 2401 here, the reverse structure in which the cathode 2404 is provided on the substrate may be employed. In the case of such an element, since a clear layer structure such as a hole transport layer is not formed, the expression “region” indicating each function is used.
[0066]
When such an element is formed, the hole transport material can receive and transport holes on the anode side, while the electron transport material can receive and transport electrons on the cathode side. Further, since the mixed region 2407 is bipolar, both holes and electrons can move through the mixed region 2407, and carriers are recombined in the mixed region 2407 to emit light. That is, unlike the mixed single layer of Document 9, a region where each function can be expressed exists in the organic compound layer 2403.
[0067]
Furthermore, in the case of the element as shown in FIG. 24, the function can be expressed and there is no organic interface as in the conventional laminated structure. Therefore, the problems (deterioration of the morphology of the organic interface and formation of the impurity layer) that occur at the organic interface described above can be solved. It is to be noted that quenching due to energy transfer to the electrodes can be prevented by separating the mixed region leading to light emission from both electrodes.
[0068]
First, the solution to the deterioration of the morphology of the organic interface will be described with reference to FIG. FIG. 25 shows an organic light emitting device represented by FIG. 24, comprising a region 2511 composed of small molecules 2501, a region 2512 composed of large molecules 2502, and a mixed region 2513 containing both small molecules 2501 and large molecules 2502. It is. As is clear from FIG. 25, the organic interface 2113 as existed in FIG. 21 does not exist, and the region 2114 having poor consistency does not exist.
[0069]
Moreover, although it is a solution of formation of an impurity layer, this is simple and clear. When an organic light emitting device as shown in FIG. 24 is manufactured, a hole transport material is vapor-deposited on the anode, and in addition to that, an electron transport material is vapor-deposited in the form of co-evaporation to form a mixed region. After forming, the electron transport material may be deposited by stopping the deposition of the hole transport material. Therefore, there is no interval that occurs when an organic light emitting device is manufactured using a vapor deposition apparatus as shown in FIG. That is, there is no gap for forming the impurity layer.
[0070]
As described above, the organic light-emitting device of the present invention does not form an organic interface, so that carrier movement is lubricated and does not adversely affect the drive voltage and the lifetime of the device. Further, since the functions are separated in the same manner as the laminated structure, there is no problem in terms of light emission efficiency.
[0071]
In addition, the conventional laminated structure is merely a hetero-junction between different kinds of materials, whereas the structure of the present invention is a so-called mixed junction, which is an organic light emitting device based on a new concept. I can say that.
[0072]
Therefore, in the present invention, in a light-emitting device including an organic light-emitting element comprising an anode, a cathode, and an organic compound layer provided between the anode and the cathode, the organic compound layer is more positive than electron mobility. A hole transport region made of a hole transport material having a high hole mobility, and an electron transport region made of an electron transport material having an electron mobility higher than the hole mobility, and the hole transport region is A mixed region including both the hole transporting material and the electron transporting material is provided between the electron transporting region and the anode transporting region, and between the hole transporting region and the electron transporting region. It is characterized by that.
[0073]
In FIG. 24, a hole injection region made of a material that enhances the hole injection property (hereinafter referred to as “hole injection material”) may be inserted between the anode and the organic compound layer. Further, an electron injection region made of a material that enhances electron injection properties (hereinafter referred to as “electron injection material”) may be inserted between the cathode and the organic compound layer. Furthermore, both a hole injection region and an electron injection region may be incorporated.
[0074]
In this case, the hole injecting material or electron injecting material is a material for reducing the carrier injection barrier from the electrode to the organic compound layer, so that the movement of carriers from the electrode to the organic compound layer is lubricated and charge is accumulated. There is an effect that can be eliminated. However, from the viewpoint of avoiding the formation of the impurity layer as described above, it is preferable to form a film without any interval between each injection material and the organic compound layer.
[0075]
By the way, in the mixed region including both the hole transport material and the electron transport material, the concentration of the hole transport material gradually decreases in the direction from the anode to the cathode, and the concentration of the electron transport material gradually increases. It is preferable to form a concentration gradient that increases from the viewpoint of carrier balance control. In the present invention, since the mixed region is also a carrier recombination region, it is desirable that the mixed region have a thickness of 10 nm or more.
[0076]
Further, as shown in FIG. 26 (a), in the organic compound layer 2603, a hole transport region 2605 made of a hole transport material, an electron transport region 2606 made of an electron transport material, and a hole transport material and an electron transport material The present invention includes a structure in which a mixed region 2607 mixed with is added and a light emitting material 2608 that emits light as a dopant is added to the mixed region 2607. Note that although the anode 2602 is provided over the substrate 2601 here, a reverse structure in which the cathode 2604 is provided over the substrate may be employed. Further, a hole injection region or an electron injection region may be provided between the electrode and the organic compound layer.
[0077]
When the light emitting material 2608 is doped into the mixed region 2607, the light emitting material 2608 traps carriers, so that the recombination rate is improved and high light emission efficiency can be expected. One of the advantages is that the emission color can be controlled by the light emitting material 2608. However, in this case, the excitation energy in the light emitting material 2608 is preferably the smallest among the compounds included in the mixed region 2607.
[0078]
Further, the light emitting region can be separated from both electrodes as much as possible to prevent quenching (hereinafter referred to as “quenching”) due to energy transfer to the electrode material. Therefore, the region where the light emitting material is doped may be a part (particularly the central portion) instead of the entire region in the mixed region.
[0079]
Furthermore, as shown in FIG. 26 (b), in the organic compound layer 2603, a hole transport region 2605 made of a hole transport material, an electron transport region 2606 made of an electron transport material, and a hole transport material and an electron transport material The present invention also includes a structure in which a mixed region 2607 in which is mixed is provided, and a blocking material 2609 is added to the mixed region 2607. Note that although the anode 2602 is provided over the substrate 2601 here, a reverse structure in which the cathode 2604 is provided over the substrate may be employed. Further, a hole injection region or an electron injection region may be provided between the electrode and the organic compound layer.
[0080]
When the blocking region 2609 is doped into the mixed region 2607, the carrier recombination rate in the mixed region 2607 is improved and diffusion of molecular excitons can be prevented, so that high light emission efficiency can be expected. However, in this case, the excitation energy level in the blocking material is preferably the highest among the materials included in the mixed region 2607.
[0081]
In addition, since the blocking material often has a function of blocking one of holes or electrons, doping the entire region in the mixed region may break the carrier balance in the mixed region. Therefore, the region where the blocking material is doped may be a part (particularly an end portion) instead of the entire region in the mixed region.
[0082]
In FIG. 26B, a light emitting material 2608 is also added as a more preferable example. That is, it is a form merged with FIG. When the blocking material 2609 has a hole blocking property, as shown in FIG. 26 (b), if the hole blocking material is added to the cathode side from the region where the light emitting material 2608 is added, the light emitting material can be efficiently used. It will emit light.
[0083]
Further, by applying the present invention to a triplet light emitting device, in addition to high luminance light emission and high light emission efficiency by light emission from a triplet excited state, the device has a very high function light emission that has a longer lifetime than that of Document 8. An element becomes possible.
[0084]
Note that since triplet molecular excitons have a diffusion length larger than that of singlet molecular excitons, it is preferable that a blocking material be included in the mixed region. That is, with reference to FIG. 26B, a material capable of converting triplet excitation energy into light emission (hereinafter referred to as “triplet light emitting material”) is used as the light emitting material 2608, and the blocking material 2609 is also added at the same time. Is desirable.
[0085]
In the following, an example more suitable for manufacturing will be described in the embodiment in which the light emitting material as shown in FIG. 26 is added. The element structure is shown in FIG.
[0086]
27, in the organic compound layer 2703 including a hole transport material and an electron transport material, a hole transport region 2705 made of a hole transport material, an electron transport region 2706 made of an electron transport material, and a hole transport material A mixed region 2707 in which the electron transport material is mixed at a constant ratio is provided, and a light emitting region is formed in the mixed region 2707 by adding a light emitting material 2708 that emits light. Although the anode 2702 is provided over the substrate 2701 here, the reverse structure in which the cathode 2704 is provided on the substrate may be employed.
[0087]
Note that the concentration profile when the concentration ratio of the hole transport material and the electron transport material in the mixed region is x: y is as shown in FIG.
[0088]
When such an element is formed, the hole transport material can receive and transport holes on the anode side, while the electron transport material can receive and transport electrons on the cathode side. Furthermore, since the mixed region 2707 is bipolar, both holes and electrons can move through the mixed region 2707. In addition, since the mixed region 2707 has a constant ratio x: y, it is easy to manufacture.
[0089]
What is important here is that a light emitting region including a light emitting material is formed in the mixed region 2707. In other words, by adding a luminescent material to the mixed region 2707, it is possible to prevent the carriers from passing through the mixed region without recombination. ")" Is also prevented.
[0090]
Therefore, in the present invention, in a light emitting device including an organic light emitting element comprising an anode, a cathode, and an organic compound layer provided between the anode and the cathode, the organic compound layer is made of a hole transport material. A hole transport region and an electron transport region made of an electron transport material, and the hole transport material and the electron transport material are in a certain ratio between the hole transport region and the electron transport region. In addition, a light-emitting region to which a light-emitting material that emits light is added is provided in the mixed region.
[0091]
Note that the light emitting material preferably has lower excitation energy than the hole transport material and the electron transport material. This is to prevent energy transfer of molecular excitons.
[0092]
In FIG. 27, a hole injection region made of a material that enhances the hole injection property (hereinafter referred to as “hole injection material”) may be inserted between the anode and the organic compound layer. Further, an electron injection region made of a material that enhances electron injection properties (hereinafter referred to as “electron injection material”) may be inserted between the cathode and the organic compound layer. Furthermore, both a hole injection region and an electron injection region may be incorporated.
[0093]
In this case, the hole injecting material or electron injecting material is a material for reducing the carrier injection barrier from the electrode to the organic compound layer, so that the movement of carriers from the electrode to the organic compound layer is lubricated and charge is accumulated. There is an effect that can be eliminated. However, from the viewpoint of avoiding the formation of the impurity layer as described above, it is preferable to form a film without any interval between each injection material and the organic compound layer.
[0094]
Further, in the mixed region, the carrier recombination portion is almost determined by the mixing ratio (the more bipolar, the closer to the center). Therefore, the luminescent material may be added to the entire region in the mixed region (FIG. 29 (a)) or may be added to a part (FIG. 29 (b)). In FIG. 29, the reference numerals in FIG. 27 are cited.
[0095]
Furthermore, as shown in FIG. 30 (a), in the organic compound layer 2703, a hole transport region 2705 made of a hole transport material, an electron transport region 2706 made of an electron transport material, and a hole transport material and an electron transport material It is assumed that the present invention also includes a structure in which a mixed region 2707 to which a light emitting material is added and a blocking material 2709 is added to the mixed region 2707 is added. Note that although the anode 2702 is provided over the substrate 2701 here, a reverse structure in which the cathode 2704 is provided over the substrate may be employed. Further, a hole injection region or an electron injection region may be provided between the electrode and the organic compound layer.
[0096]
Note that the blocking material in this case is preferably a material having the highest excitation energy level among the materials included in the mixed region 2707 and the function of blocking carriers or the function of preventing diffusion of molecular excitons. When the blocking material 2709 is added to the mixed region 2707, the carrier recombination rate in the mixed region 2707 is improved, and diffusion of molecular excitons can be prevented, so that high light emission efficiency can be expected. However, since the blocking material often has a function of blocking one of holes or electrons, if added to the entire region in the mixed region, the carrier balance in the mixed region may be lost. Therefore, the region where the blocking material is added is not the entire region within the mixing region, but a part thereof.
[0097]
As the blocking material, a material having a low HOMO level, that is, a material capable of blocking holes is usually effective. Therefore, as shown in FIG. 30 (b), a technique in which a blocking material is added to the cathode side from a region where the light emitting material 2708 is added is useful.
[0098]
Furthermore, by applying a triplet light emitting material as a light emitting material to be added to such an element structure, in addition to high luminance light emission and high light emission efficiency by light emission from a triplet excited state, the life of the element is very long. A highly functional light emitting element can be realized. Note that since triplet molecular excitons have a diffusion length larger than that of singlet molecular excitons, it is preferable that a blocking material be included in the mixed region.
[0099]
By the way, since the mixed region composed of the hole transport material and the electron transport material as described above needs to be bipolar, in the mixed region, a positive value relative to the total mass of the hole transport material and the electron transport material is required. The percentage of the mass of the hole transport material is preferably 10% or more and 90% or less. However, this ratio is considered to vary greatly depending on the combination of materials.
[0100]
In addition, since the mixed region composed of the hole transport material and the electron transport material includes a light emitting region, that is, a carrier recombination region, a certain thickness is required so that carriers do not pass through. Therefore, it is desirable that the mixed region has a thickness of 10 nm or more. Moreover, considering that the resistance of the bipolar region is high, it is desirable to be 100 nm or less.
[0101]
By implementing the invention as described above, it is possible to provide a light emitting device having a driving voltage lower than that of a conventional device and having a long lifetime. Furthermore, by producing an electric appliance using the light emitting device, it is possible to provide an electric appliance that consumes less power than the conventional one and is kept long.
[0102]
DETAILED DESCRIPTION OF THE INVENTION
Below, the form at the time of implementing this invention is described. Note that an organic light-emitting element only needs to have at least one of an anode and a cathode transparent in order to extract light emission, but in this embodiment, the element structure is such that a transparent anode is formed on a substrate and light is extracted from the anode. Describe. In practice, a structure in which light is extracted from the cathode or a structure in which light is extracted from the side opposite to the substrate is also applicable.
[0103]
First, an embodiment of an organic light emitting device in which a hole transporting mixed layer is formed will be described with reference to FIG. FIG. 5 illustrates a structure in which a hole-transporting mixed layer 503, a light-emitting layer 504, an electron-transporting layer 505, and a cathode 506 are stacked on a substrate 501 having an anode 502. Note that the light-emitting layer 504 is not inserted, and the hole-transporting mixed layer 503 or the electron-transport layer 505 can emit light. The hole transporting mixed layer 503 is formed by mixing both a hole injecting material and a hole transporting material.
[0104]
As shown in FIG. 2, the hole transporting mixed layer 503 may have a concentration gradient formed of a hole injection material and a hole transport material. In this case, when a highly insulating material such as aluminum oxide is used as the hole injecting material, it is preferable that the concentration gradient of the hole injecting material is steep (decays immediately as the distance from the anode increases).
[0105]
Next, an embodiment of an organic light emitting device having an electron transporting mixed layer will be described with reference to FIG. FIG. 6 shows a structure in which a hole transport layer 603, a light emitting layer 604, an electron transporting mixed layer 605, and a cathode 606 are stacked on a substrate 601 having an anode 602. Note that the light-emitting layer 604 is not inserted, and the electron-transporting mixed layer 605 or the hole-transporting layer 603 can emit light. The electron transporting mixed layer 605 is formed by mixing both an electron injecting material and an electron transporting material.
[0106]
Note that the electron transporting mixed layer 605 may have a concentration gradient formed of an electron injection material and an electron transport material, as shown in FIG. In this case, when a highly insulating material such as lithium fluoride is used as the electron injecting material, the concentration gradient of the electron injecting material is preferably steep (decays immediately).
[0107]
Next, an embodiment of an organic light emitting device in which a bipolar mixed layer is formed will be described with reference to FIG. FIG. 7 shows a structure in which a hole injection layer 703, a bipolar mixed layer 704, an electron injection layer 705, and a cathode 706 are stacked on a substrate 701 having an anode 702. The bipolar mixed layer 704 is formed by mixing both a hole transport material and an electron transport material.
[0108]
Note that the bipolar mixed layer 704 may have a concentration gradient formed of a hole transport material and an electron transport material, as shown in FIG.
[0109]
Further, as shown in FIG. 24, the constituent material of the hole transport region 2405 is used as the hole transport material included in the mixed region 2407, and the constituent material of the electron transport region 2406 is used as the electron transport material included in the mixed region 2407. Accordingly, the mixed region 2407, the hole transport region 2405, and the electron transport region 2406 may be continuously joined. In this case, there is an advantage that two kinds of compounds (a hole transport material and an electron transport material) can play the role of three layers in the conventional case, ie, a hole transport region, a light emitting region, and an electron transport region. Although not shown in FIG. 24, a hole injection layer may be inserted between the anode 2402 and the hole transport region 2405, and an electron injection layer may be inserted between the cathode 2404 and the electron transport region 2406.
[0110]
By implementing such an element structure, formation of an impurity layer can be prevented, but in this case, a manufacturing process for manufacturing an organic light emitting element becomes important. Therefore, an example suitable for the manufacturing method of such an element structure will be described.
[0111]
The conceptual diagram of a vapor deposition apparatus is shown in FIG. FIG. 31A is a top view of the single chamber system in which one vacuum chamber 3110 is installed as a vapor deposition chamber, and a plurality of vapor deposition sources are provided in the vacuum chamber. In addition, materials having different functions such as a hole injection material, a hole transport material, an electron transport material, an electron injection material, a blocking material, a light emitting material, and a cathode constituent material are separately stored in the plurality of vapor deposition sources. ing.
[0112]
In a vapor deposition apparatus having such a vapor deposition chamber, first, a substrate having an anode (ITO or the like) is carried into a carry-in chamber, and when the anode is an oxide such as ITO, an oxidation treatment is performed in the pretreatment chamber. (Although not shown in FIG. 31 (a), an ultraviolet irradiation chamber may be provided to clean the anode surface). Further, all the materials forming the organic light emitting device are deposited in the vacuum chamber 3110. However, the cathode may be formed in the vacuum chamber 3110, or a vapor deposition chamber may be provided separately to form the cathode there. The point is that vapor deposition is performed in one vacuum chamber 3110 until the cathode is formed. Finally, sealing is performed in the sealing chamber, and the organic light emitting device is obtained by taking out from the unloading chamber via the transfer chamber.
[0113]
A procedure for manufacturing the organic light-emitting element of the present invention using such a single chamber deposition apparatus will be described with reference to FIG. 31B (a cross-sectional view of the vacuum chamber 3110). In FIG. 31 (b), for simplification of the drawing, a vacuum chamber 3110 having two vapor deposition sources (an organic compound vapor deposition source a3118 and an organic compound vapor deposition source b3119) is used, and is composed of a hole transport material 3116 and an electron transport material 3117. The process of forming an organic compound layer is shown.
[0114]
First, a substrate 3101 having an anode 3102 is carried into a vacuum chamber 3110 and fixed by a fixing table 3111 (usually, the substrate is rotated during vapor deposition). Next, the inside of the vacuum chamber 3110 is decompressed (10 ^-Four After that, the container a3112 is heated to evaporate the hole transport material 3116, and after reaching a predetermined deposition rate (unit: [Å / s]), the shutter a3114 is opened and deposition is started. At this time, the container b3113 is also heated while the shutter b3115 is closed.
[0115]
Thereafter, the shutter b3115 is opened while the shutter a3114 remains open, whereby the electron transport material 3117 is co-evaporated (the state shown in FIG. 31B), and the mixed region 3104 is formed after the hole transport region 3103. By this operation, no impurity layer is mixed between the hole transport region 3103 and the mixed region 3104.
[0116]
Further, in order to form an electron transport region, the shutter a3114 is closed while the shutter b3115 is opened, and the heating of the container a3112 is finished. By this operation, no impurity layer is formed between the mixed region 3104 and the electron transport region.
[0117]
Furthermore, there is also a method of causing the mixed region 2607 shown in FIG. In this case, the light emitting material which is a dopant needs to have lower excitation energy than the hole transport material and the electron transport material included in the mixed region 2607.
[0118]
Even when the light emitting material is doped as described above, the manufacturing process for manufacturing the organic light emitting element is important in order to prevent the formation of the impurity layer. Below, the manufacturing method is described.
[0119]
FIG. 32 (a) is a top view of the vapor deposition apparatus, but is a single chamber system in which one vacuum chamber 3210 is installed as a vapor deposition chamber and a plurality of vapor deposition sources are provided in the vacuum chamber. In addition, materials having different functions such as a hole injection material, a hole transport material, an electron transport material, an electron injection material, a blocking material, a light emitting material, and a cathode constituent material are separately stored in the plurality of vapor deposition sources. ing.
[0120]
In a vapor deposition apparatus having such a vapor deposition chamber, first, a substrate having an anode (ITO or the like) is carried into a carry-in chamber, and when the anode is an oxide such as ITO, an oxidation treatment is performed in the pretreatment chamber. (Note that although not shown in FIG. 32 (a), an ultraviolet irradiation chamber may be provided to clean the anode surface). Further, all materials forming the organic light emitting device are deposited in the vacuum chamber 3210. However, the cathode may be formed in the vacuum chamber 3210, or a vapor deposition chamber may be provided separately to form the cathode there. The point is that vapor deposition is performed in one vacuum chamber 3210 until the cathode is formed. Finally, sealing is performed in the sealing chamber, and the organic light emitting device is obtained by taking out from the unloading chamber via the transfer chamber.
[0121]
A procedure for manufacturing the organic light-emitting element of the present invention using such a single chamber deposition apparatus will be described with reference to FIG. 32B (a cross-sectional view of the vacuum chamber 3210). In FIG. 32 (b), as the simplest example, a vacuum chamber 3210 having three vapor deposition sources (organic compound vapor deposition source a3216, organic compound vapor deposition source b3217, and organic compound vapor deposition source c3218) is used, and a hole transport material 3221, A process of forming an organic compound layer including an electron transport material 3222 and a light emitting material 3223 is shown.
[0122]
First, a substrate 3201 having an anode 3202 is carried into a vacuum chamber 3210 and fixed by a fixing table 3211 (usually, the substrate is rotated during vapor deposition). Next, the vacuum chamber 3210 is depressurized (10 ^-Four After that, the container a3212 is heated to evaporate the hole transport material 3221, and after reaching a predetermined deposition rate (unit: [nm / s]), the shutter a3214 is opened and deposition is started. At this time, the container b3213 is also heated while the shutter b3215 is closed.
[0123]
After that, by opening the shutter b3215 while keeping the shutter a3214 open, the electron transport material 3222 is co-evaporated to form the mixed region 3204 after the hole transport region 3203. By this operation, the impurity layer is not mixed between the hole transport region 3203 and the mixed region 3204. Here, when the mixed region 904 is formed, a small amount of the light emitting material 3223 is also added in the middle (the state shown in FIG. 32B).
[0124]
Further, in order to form an electron transport region, the shutter a3214 is closed while the shutter b3215 is opened, and the heating of the container a3212 is finished. By this operation, no impurity layer is formed between the mixed region 3204 and the electron transport region.
[0125]
By applying this method, all the organic light-emitting elements described in the means for solving the problems can be manufactured. For example, when a blocking material is added to the mixed region 3204, an evaporation source for evaporating the blocking material may be installed in FIG. 32 (b) and evaporated during formation of the mixed region.
[0126]
Further, even when the hole injection region or the electron injection region is formed, the vapor deposition source of each injection material may be installed in the same vacuum chamber 3210. For example, in FIG. 32B, when a hole injection region is provided between the anode 3202 and the hole transport region 3203 by vapor deposition, the hole injection material is vapor deposited on the anode 3202, and then immediately without any interval. By evaporating the hole transport material 3221, formation of an impurity layer can be avoided.
[0127]
Since a concentration gradient can also be formed in the mixed region described above, an example of a concentration gradient forming method will be described here. Here, a case where a film can be formed by vacuum evaporation by resistance heating will be described. Regarding the method of forming the concentration gradient, when the evaporation temperature of the material and the vapor deposition rate (usually the unit is nm / s) are correlated, the vapor deposition rate can be controlled by temperature control. However, the thermal conductivity of the organic material usually used in a powder form is particularly poor, and control by temperature tends to cause unevenness. Therefore, it is preferable to prepare two kinds of materials for forming a concentration gradient in different vapor deposition sources, and perform vapor deposition rate control using a shutter (the film thickness is monitored by a crystal resonator). The form is shown in FIG.
[0128]
In FIG. 11, a method for forming a concentration gradient will be described using the element structure shown in FIG. 24 as an example. Therefore, in FIG. 11, the reference numerals used in FIG. 24 are cited. First, a substrate 1101 having an anode 1102 is carried into a film formation chamber 1110 and fixed on a fixing table 1111 (usually, the substrate is rotated during vapor deposition).
[0129]
Next, the sample chamber a1112 in which the hole transport material 1116 is placed is heated, and the shutter a1114 is opened, whereby a hole transport region 2405 made of the hole transport material 1116 is formed. At this time, the sample chamber b1113 in which the electron transport material 1117 is installed is also heated at the same time, but the shutter b1115 is closed.
[0130]
After the hole transport region 2405 reaches a predetermined film thickness, the shutter a1114 is gradually closed, and at the same time, the shutter b1115 is gradually opened. The concentration gradient of the mixed region 2407 is formed by the opening / closing speed at this time. The opening / closing speed is such that when the shutter a1114 is completely closed, the mixed region 2407 reaches a predetermined film thickness, and the electron transport material 1117 has a predetermined deposition rate (a rate at which the electron transport region 2406 is deposited). It can be set to reach Thereafter, the electron transport region 2406 is formed while the shutter b1115 is opened, and an element having a concentration gradient in the element structure of FIG. 24 becomes possible.
[0131]
Note that this method can be applied to all cases where a concentration gradient is formed in an element structure other than that shown in FIG. In addition, when the light emitting material is doped into the bipolar mixed layer or the mixed region, the number of vapor deposition sources in FIG. 11 is increased by one, and the shutter of the dopant vapor deposition source may be opened only during the doping time period.
[0132]
However, the means for forming the concentration gradient is not limited to this method.
[0133]
Incidentally, some embodiments as described above can be used in combination. For example, the hole transporting mixed layer, the electron transporting mixed layer, and the bipolar mixed layer are applied in combination. An example is shown in FIG.
[0134]
The element structure shown in FIG. 8 includes a hole transporting mixed layer 803 made of a hole injection material 811 and a hole transport material 812, a hole transport material 812, and an electron transport material 813 on a substrate 801 having an anode 802. A bipolar mixed layer 804, an electron transporting mixed layer 805 made of an electron transporting material 813 and an electron injecting material 814, and a cathode 806 are laminated.
[0135]
In this embodiment mode, a light emitting region 807 doped with a small amount of a light emitting material 815 is provided in the bipolar mixed layer 804. In each layer, a concentration gradient as shown in graph 810 was formed. FIG. 19 shows a schematic diagram of an expected band diagram when such a concentration gradient is formed.
[0136]
With this element structure, a conventional four-layer structure (FIG. 19 (a)) of a hole injection layer, a hole transport layer, an electron transport layer, and an electron injection layer can be accommodated in a three-layer structure (FIG. 19 (b)). It will be. Moreover, as shown in FIG. 19B, each mixed layer has only a gentle energy barrier, and each mixed layer is continuously joined by the hole transport material 812 and the electron transport material 813, It is advantageous for movement.
[0137]
Next, an embodiment in which the element in which the mixed layers are combined as described above is applied to a triplet light emitting element will be described. Usually, the basic structure of a triplet light emitting element is an element structure as shown in FIG. That is, a substrate 901, an anode 902, a hole transport layer 903, a light emitting layer 904 formed by doping a host material with a triplet light emitting material, a blocking layer 905, an electron transport layer 906, and a cathode 907. The blocking layer 905 is made of a blocking material, blocks holes and increases the carrier recombination efficiency in the light emitting layer 904, and also serves to prevent diffusion of molecular excitons generated in the light emitting layer 904. It is also an electron transporting material.
[0138]
The light emission efficiency can be further increased by providing a hole injection layer or an electron injection layer in the element structure of FIG. However, in addition to the five-layer structure as shown in FIG. 9, the number of interfaces is further increased by increasing the number of layers. Therefore, the present invention is applied.
[0139]
That is, in FIG. 9, the hole transport layer 903 is a hole transporting mixed layer composed of a hole injection material and a hole transport material, and the light emitting layer 904 is composed of a hole transport material and a host material of the light emitting layer. For example, a bipolar mixed layer may be used, and the electron transport layer 906 may be an electron transport mixed layer including an electron transport material and an electron injection material. The triplet light emitting material may be doped in a portion where the host material of the light emitting layer is present. It is also effective to form a concentration gradient in each mixed layer as shown in FIGS.
[0140]
In FIG. 9, the blocking layer 905 is used as a single layer, but when the present invention is carried out, it may be mixed with the host material of the light emitting layer (that is, a blocking mixed layer may be formed). Good). However, from the viewpoint of preventing diffusion of molecular excitons, it is preferable to form a concentration gradient so that the blocking material has a high concentration on the cathode side.
[0141]
Based on the above, FIG. 10 shows an example of an embodiment in which an element in which each mixed layer is combined is applied to a triplet light emitting element. That is, on a substrate 1001 having an anode 1002, a hole transporting mixed layer 1003 composed of a hole injection material 1011 and a hole transporting material 1012, a bipolar mixed layer 1004 composed of a hole transporting material 1012 and a host material 1013, A blocking mixed layer 1005 composed of a host material 1013 and a blocking material 1014, an electron transporting mixed layer 1006 composed of a blocking material 1014 (also serving as an electron transport material in this case) and an electron injection material 1015, and a cathode 1007 were laminated. Is. A concentration gradient as shown in the graph 1010 was formed in each layer.
[0142]
Note that since this embodiment mode is a triplet light emitting element, a light emitting region 1008 doped with a small amount of a triplet light emitting material 1016 is provided. The light emitting region 1008 is preferably installed in a region where the concentration of the host material 1013 is high as shown in FIG. FIG. 20B shows a schematic diagram of an expected band diagram when a concentration gradient as shown in the graph 1010 is formed.
[0143]
According to this element structure, conventionally, a five-layer structure (FIG. 20 (a)) consisting of a hole injection layer, a hole transport layer, a light emitting layer, a blocking layer (also serving as an electron transport layer), and an electron injection layer is a four-layer structure. (FIG. 20B). Moreover, as shown in FIG. 20B, each mixed layer has only a gentle energy barrier, and each mixed layer has a hole transport material 1012, a host material 1013, and a blocking material 1014 (also serving as an electron transport material). Are continuously joined, which is advantageous for carrier movement.
[0144]
Finally, materials suitable for a hole injection material, a hole transport material, an electron transport material, an electron injection material, a blocking material, a light emitting material, a constituent material of a cathode, and the like are listed below. However, the material used for the organic light emitting device of the present invention is not limited to these.
[0145]
As the hole injection material, a porphyrin-based compound is effective as long as it is an organic compound, such as phthalocyanine (abbreviation: H2Pc) and copper phthalocyanine (abbreviation: CuPc). There are also materials in which conductive polymer compounds are chemically doped. Polyethylenedioxythiophene (abbreviation: PEDOT) doped with polystyrene sulfonic acid (abbreviation: PSS), polyaniline (abbreviation: PAni), polyvinylcarbazole (abbreviation: PVK) ) And the like. An insulating polymer compound is also effective in planarizing the anode, and polyimide (abbreviation: PI) is often used. In addition, inorganic compounds are also used. In addition to metal thin films such as gold and platinum, there are ultra thin films of aluminum oxide (alumina).
[0146]
The most widely used hole transport material is an aromatic amine-based compound (that is, a compound having a benzene ring-nitrogen bond). As a widely used material, in addition to the above-mentioned TPD, its derivative 4,4′-bis [N- (1-naphthyl) -N-phenyl-amino] -biphenyl (abbreviation: α-NPD) 4,4 ′, 4 ″ -tris (N, N-diphenyl-amino) -triphenylamine (abbreviation: TDATA), 4,4 ′, 4 ″ -tris [N- (3-methylphenyl) And starburst aromatic amine compounds such as -N-phenyl-amino] -triphenylamine (abbreviation: MTDATA).
[0147]
As electron transport materials, metal complexes are often used, and the Alq described above is used. _Three And tris (4-methyl-8-quinolinolato) aluminum (abbreviation: Al (mq _Three )), Bis (10-hydroxybenzo [h] -quinolinato) beryllium (abbreviation: Be (Bq) ₂ ) And other metal complexes having a quinoline skeleton or a benzoquinoline skeleton, and mixed ligand complexes such as bis (2-methyl-8-quinolinolato)-(4-phenylphenolato) -aluminum (abbreviation: BAlq). . In addition, bis [2- (2-hydroxyphenyl) -benzoxazolate] zinc (abbreviation: Zn (BOX) ₂ ), Bis [2- (2-hydroxyphenyl) -benzothiazolate] zinc (abbreviation: Zn (BTZ) ₂ There are also metal complexes having an oxazole-based or thiazole-based ligand. In addition to metal complexes, 2- (4-biphenylyl) -5- (4-tert-butylphenyl) -1,3,4-oxadiazole (abbreviation: PBD), 1,3-bis [5- Oxadiazole derivatives such as (p-tert-butylphenyl) -1,3,4-oxadiazol-2-yl] benzene (abbreviation: OXD-7), 5- (4-biphenylyl) -3- (4 -Tert-butylphenyl) -4-phenyl-1,2,4-triazole (abbreviation: TAZ), 5- (4-biphenylyl) -3- (4-tert-butylphenyl) -4- (4-ethylphenyl) ) -1,2,4-triazole (abbreviation: p-EtTAZ) and other phenanthroline derivatives such as bathophenanthroline (abbreviation: BPhen) and bathocuproin (abbreviation: BCP) have electron transport properties.
[0148]
The electron transport material described above can be used as the electron injection material. In addition, an ultra-thin film of an insulator such as an alkali metal halide such as lithium fluoride or an alkali metal oxide such as lithium oxide is often used. In addition, alkali metal complexes such as lithium acetylacetonate (abbreviation: Li (acac)) and 8-quinolinolato-lithium (abbreviation: Liq) are also effective.
[0149]
As the blocking material, BAlq, OXD-7, TAZ, p-EtTAZ, BPhen, BCP and the like described above are effective because of their high excitation energy level.
[0150]
Light emitting materials (including those used as dopants) include the Alq described above. _Three , Al (mq) _Three , Be (Bq) ₂ , BAlq, Zn (BOX) ₂ , Zn (BTZ) ₂ In addition to metal complexes such as these, various fluorescent dyes are effective. A triplet light emitting material is also possible, and is mainly a complex having platinum or iridium as a central metal. As a triplet light-emitting material, tris (2-phenylpyridine) iridium (abbreviation: Ir (ppy) _Three ), 2, 3, 7, 8, 12, 13, 17, 18-octaethyl-21H, 23H-porphyrin-platinum (abbreviation: PtOEP) and the like are known.
[0151]
By combining the materials having the respective functions as described above and applying them to the organic light emitting device of the present invention, it is possible to produce an organic light emitting device having a lower driving voltage and a longer device life than conventional ones. it can.
[0152]
【Example】
[Example 1]
In this example, a device to which a hole transporting mixed layer is applied as shown in FIG. 5 in the embodiment of the invention is specifically illustrated.
[0153]
First, indium tin oxide (hereinafter referred to as “ITO”) is formed to a thickness of about 100 nm on the glass substrate 501 by sputtering to form the anode 502. Next, the hole transporting mixed layer 503 is formed by co-evaporating CuPc as the hole injection material and α-NPD as the hole transport material at a deposition rate ratio of 1: 1. The film thickness is 50 nm.
[0154]
Further, as the light emitting layer 504, Alq _Three A 10 nm layer of rubrene doped with 5 wt% is laminated. Finally, Alq as the electron transport layer 505 _Three Is formed with an Al: Li alloy (Li is 0.5 wt% in mass ratio) of about 150 nm as a cathode 506, whereby a yellow light emitting organic light emitting element derived from rubrene can be produced.
[0155]
[Example 2]
In this example, a device to which an electron transporting mixed layer is applied as shown in FIG. 6 in the embodiment of the invention is specifically illustrated.
[0156]
First, ITO is deposited on the glass substrate 601 by sputtering to a thickness of about 100 nm to form an anode 602. Next, the hole transport layer 603 is formed by depositing 50 nm of α-NPD which is a hole transport material.
[0157]
Furthermore, after laminating 10 nm of perylene as the light emitting layer 604, BPhen, which is an electron transport material, and Alq, which is an electron injection material. _Three Are co-evaporated at a deposition rate ratio of 1: 1 to form the electron transporting mixed layer 605. The film thickness is 40 nm. Finally, an Al: Li alloy (Li is 0.5 wt% in weight ratio) is formed to a thickness of about 150 nm as the cathode 606, whereby a blue light emitting organic light emitting element derived from perylene can be produced.
[0158]
[Example 3]
In this example, an organic light emitting device in which a hole injection region made of a hole injection material is inserted between the anode 2402 and the organic compound layer 2403 in the organic light emitting device shown in FIG.
[0159]
First, a glass substrate 2401 on which an anode 2402 is formed by depositing ITO with a thickness of about 100 nm is prepared. The glass substrate 2401 having the anode 2402 is carried into a vacuum chamber as shown in FIG. In this embodiment, four kinds of materials (three kinds are organic compounds and one kind is a metal that becomes a cathode) are vapor deposited, so that four vapor deposition sources are required.
[0160]
First, CuPc, which is a hole injection material, is deposited to 20 nm, but the deposition of CuPc reaches 20 nm, and at the same time, deposition of α-NPD, which is a hole transport material, is deposited at 0.3 nm / s without any interval. Start with a rate. The reason for not leaving the interval is to prevent the formation of the impurity layer as described above.
[0161]
After forming the hole transport region 2405 consisting of only α-NPD to 30 nm, the deposition rate of α-NPD is fixed at 0.3 nm / s, and the electron transport material Alq _Three Vapor deposition starts at 0.3 nm / s. That is, α-NPD and Alq _Three A mixed region 2407 having a rate ratio of 1: 1 is formed by co-evaporation.
[0162]
After the mixed region 2407 reaches 30 nm, α-NPD ends the deposition, and Alq _Three Only by continuing the deposition, the electron transport region 2406 is formed. The thickness is 40 nm. Finally, by depositing about 150 nm of Al: Li alloy as the cathode, Alq _Three A green light emitting organic light emitting device derived from the above is obtained.
[0163]
[Example 4]
In this example, in the organic light emitting device shown in FIG. 29A, an organic light emitting device in which a hole injection region made of a hole injection material is inserted between the anode 2702 and the organic compound layer 2703 is specifically described. Illustrate.
[0164]
First, a glass substrate 2701 on which ITO is formed to a thickness of about 100 nm by sputtering and an anode 2702 is formed is prepared. The glass substrate 2701 having the anode 2702 is carried into a vacuum chamber as shown in FIG. In this embodiment, five kinds of materials (four kinds are organic compounds and one kind is a metal to be a cathode) are vapor deposited, so that five vapor deposition sources are required.
[0165]
First, CuPc, which is a hole injection material, is deposited to 20 nm, but the deposition of CuPc reaches 20 nm, and at the same time, deposition of α-NPD, which is a hole transport material, is deposited at 0.3 nm / s without any interval. Start with a rate. The reason for not leaving the interval is to prevent the formation of the impurity layer as described above.
[0166]
After forming the hole transport region 2705 consisting only of α-NPD to 30 nm, the deposition rate of α-NPD is fixed at 0.3 nm / s, and the electron transport material Alq _Three Vapor deposition starts at 0.3 nm / s. That is, α-NPD and Alq _Three A mixed region 2707 having a rate ratio of 1: 1 is formed by co-evaporation. At the same time, 4- (dicyanomethylene) -2-methyl-6- (p-dimethylaminostyryl) -4H-pyran (abbreviation: DCM), which is a fluorescent dye, is added as the light-emitting material 2708. The ratio is Alq _Three : The deposition rate is controlled so that DCM = 50: 1.
[0167]
After the mixed region 2707 reaches 30 nm, α-NPD and DCM finish the deposition and Alq _Three Only by continuing the deposition, the electron transport region 2706 is formed. The thickness is 40 nm. Finally, an Al: Li alloy is deposited as a cathode to a thickness of about 150 nm to obtain a red light emitting organic light emitting device derived from DCM.
[0168]
[Example 5]
In this example, the organic light emitting device shown in FIG. 29B is specifically exemplified.
[0169]
First, a glass substrate 2701 on which ITO is formed to a thickness of about 100 nm by sputtering and an anode 2702 is formed is prepared. The glass substrate 2701 having the anode 2702 is carried into a vacuum chamber as shown in FIG. In this embodiment, four kinds of materials (three kinds are organic compounds and one kind is a metal that becomes a cathode) are vapor deposited, so that four vapor deposition sources are required.
[0170]
First, after forming 40 nm of hole transport region 2705 consisting only of α-NPD which is a hole transport material, the deposition rate of α-NPD is fixed at 0.3 nm / s, while Alq which is an electron transport material is Alq. _Three Vapor deposition starts at 0.3 nm / s. That is, α-NPD and Alq _Three A mixed region 2707 having a rate ratio of 1: 1 is formed by co-evaporation.
[0171]
The mixed region 2707 is formed to have a thickness of 30 nm. At this time, an intermediate 10 nm in the mixed region 2707 (that is, between 10 nm to 20 nm in the mixed region 30 nm) is 4- (dicyanomethylene) -2-methyl which is a fluorescent dye. -6- (p-dimethylaminostyryl) -4H-pyran (hereinafter referred to as “DCM”) is doped as a light emitting material 2708 at a ratio of about 1 wt%.
[0172]
After the mixed region reaches 30 nm, α-NPD finishes the deposition and Alq _Three Only by continuing the deposition, the electron transport region 2706 is formed. The thickness is 40 nm. Finally, an Al: Li alloy is deposited as a cathode to a thickness of about 150 nm to obtain a red light emitting organic light emitting device derived from DCM.
[0173]
[Example 6]
In this example, a device in which a concentration gradient is applied to the device to which the mixed region as shown in FIG. 26A in the embodiment of the invention is applied is specifically exemplified. In order to form a concentration gradient, an element is manufactured using an apparatus as shown in FIG. In the case of the present embodiment, three kinds of vapor deposition sources are required: a hole transport material, an electron transport material, and a light emitting material.
[0174]
First, an ITO film is formed to a thickness of about 100 nm on a glass substrate 2601 by sputtering to form an anode 2602. Next, a hole transport region 2605 is formed by depositing α-NPD which is a hole transport material to a thickness of 40 nm.
[0175]
Furthermore, as described in the embodiment of the invention, the electron transport material (Alq in this example) is simultaneously closed while the shutter of the deposition source of the hole transport material (α-NPD) is gradually closed. _Three Α-NPD and Alq by gradually opening the shutter of the vapor deposition source _Three A mixed region 2607 having a concentration gradient consisting of At this time, rubrene is doped at a rate of about 5 wt% as a light emitting material 2608 in a 10 nm region located in the middle of the 20 nm thickness of the mixed region 2607.
[0176]
After the mixed region reaches 20 nm, the electron transport material (Alq _Three ) Alq with only the shutter of the evaporation source opened _Three An electron transport region 2606 is formed. Finally, an Al: Li alloy (Li is 0.5 wt% by weight) is formed to a thickness of about 150 nm as the cathode 2604, whereby a yellow light-emitting organic light-emitting element derived from rubrene can be produced.
[0177]
[Example 7]
In this example, in the organic light emitting device shown in FIG. 26B, a hole injection region made of a hole injection material is inserted between the anode 2602 and the organic compound layer 2603, and the cathode 2604 and the organic compound layer 2603 are inserted. An organic light emitting device in which an electron injection region made of an electron injection material is inserted between them will be specifically illustrated.
[0178]
First, a glass substrate 2601 on which an anode 2602 is formed by depositing ITO to a thickness of about 100 nm is prepared. The glass substrate 2601 having the anode 2602 is carried into a vacuum chamber as shown in FIG. In the present embodiment, seven types of materials (6 types are organic compounds and one type is a metal to be a cathode) are vapor-deposited, so seven vapor deposition sources are required.
[0179]
First, CuPc, which is a hole injection material, is deposited by 20 nm. At the same time as the deposition of CuPc reaches 20 nm, deposition of TPD, which is a hole transport material, is performed at a deposition rate of 0.2 nm / s. Start. The reason for not leaving the interval is to prevent the formation of the impurity layer as described above.
[0180]
After forming the hole transport region 2605 consisting only of TPD to 30 nm, the deposition rate of TPD is fixed at 0.2 nm / s, and the electron transport material BeBq ₂ The vapor deposition starts at 0.8nm / s. That is, TPD and BeBq ₂ A mixed region 2607 having a rate ratio of 1: 4 is formed by co-evaporation.
[0181]
The mixed region 2607 is formed to have a thickness of 30 nm. At this time, the middle 10 nm in the mixed region 2607 (that is, between 10 nm to 20 nm in the mixed region 30 nm) is about 5 wt% of rubrene, which is a fluorescent dye, as the light emitting material 2608 Dope at a rate of. The last 10 nm in the mixed region 2607 (that is, between 20 nm and 30 nm in the mixed region 30 nm) is doped with BCP as the blocking material 2609. The deposition rate ratio of each material during BCP doping is TPD: BeBq ₂ : BCP = 1: 4: 3.
[0182]
After the mixed region 2607 reaches 30 nm, TPD and BCP finish the deposition, BeBq ₂ Only by continuing the deposition, the electron transport region 2606 is formed. The thickness is 40 nm. BeBq ₂ At the same time, the deposition of Li (acac), which is an electron injection material, is started to deposit about 2 nm without leaving an interval. The reason for not leaving the interval is to prevent the formation of the impurity layer as described above.
[0183]
Finally, aluminum is deposited as a cathode to a thickness of about 150 nm to obtain a yellow light emitting organic light emitting element derived from rubrene.
[0184]
[Example 8]
In this example, the organic light emitting device shown in FIG. 30B is specifically exemplified.
[0185]
First, a glass substrate 2701 on which ITO is formed to a thickness of about 100 nm by sputtering and an anode 2702 is formed is prepared. The glass substrate 2701 having the anode 2702 is carried into a vacuum chamber as shown in FIG. In this embodiment, five kinds of materials (four kinds are organic compounds and one kind is a metal to be a cathode) are vapor deposited, so that five vapor deposition sources are required.
[0186]
First, after forming a hole transport region 2705 consisting only of MTDATA, which is a hole transport material, to 40 nm, the deposition rate of MTDATA is fixed at 0.3 nm / s, while the deposition of PBD, which is an electron transport material, is also 0.3 nm / s. Start with. That is, a mixed region 2707 in which the ratio of MTDATA and PBD is 1: 1 is formed by co-evaporation.
[0187]
The mixed region 2707 is formed to have a thickness of 30 nm. At this time, in the middle 10 nm in the mixed region 2707 (that is, between 10 nm to 20 nm in the mixed region 30 nm), perylene as a fluorescent dye is added as the light emitting material 2708. The deposition rate is controlled so that the ratio is MTDATA: PBD: perylene = 4: 16: 1. Further, the last 10 nm in the mixed region 2707 (that is, between 20 nm and 30 nm in the mixed region 30 nm) is added with BCP as the blocking material 2709, and the rate ratio thereof is MTDATA: PBD: BCP = 1: 4. : 5.
[0188]
After the mixed region reaches 30 nm, MTDATA and BCP finish the deposition, and only the PBD is continuously deposited to form the electron transport region 2706. The thickness is 40 nm. Finally, an Al: Li alloy is deposited as a cathode to a thickness of about 150 nm to obtain a blue light emitting organic light emitting device derived from perylene.
[0189]
[Example 9]
In this example, a device in which a hole transporting mixed layer / bipolar mixed layer / electron transporting mixed layer is applied in combination as shown in FIG. . In this embodiment, in order to form a concentration gradient (graph 810 in FIG. 8), an evaporation source with a shutter as shown in FIG.
[0190]
First, an ITO film is formed to a thickness of about 100 nm on a glass substrate 801 by sputtering to form an anode 802. Next, a hole transporting mixed layer 803 made of CuPc as the hole injection material 811 and α-NPD as the hole transport material 812 is formed to a thickness of 40 nm. At this time, a density gradient as shown in graph 810 is formed by opening and closing the shutter.
[0191]
This time, the shutter of the deposition source of α-NPD is gradually closed, and at the same time, Alq which is the electron transport material 813 _Three By gradually opening the shutter of the evaporation source, a bipolar mixed layer 804 having a concentration gradient is formed to a thickness of 20 nm. At this time, the 10 nm region 807 located in the middle of the 20 nm thickness of the bipolar mixed layer 804 is 4- (dicyanomethylene) -2-methyl-6- (p-dimethylaminostyryl) -4H which is the light emitting material 815. -Doping with 1% by weight of pyran (hereinafter referred to as "DCM").
[0192]
After the bipolar mixed layer 804 reaches 20 nm, Alq _Three Alq with only the shutter open _Three Is deposited by 35 nm. In the last 5 nm region, Alq _Three At the same time as the deposition source shutter is gradually closed, the shutter of the deposition source of Li (acac) which is the electron injection material 814 is gradually opened to form the electron transporting mixed layer 805 having a total of 40 nm. In other words, the concentration gradient of Li (acac) is set steeply (in the graph 810, the inclination of the electron injection material 814 is constant, but in this embodiment, it rises sharply only at the end. become).
[0193]
Finally, by depositing about 150 nm of Al as the cathode 806, a red light-emitting organic light-emitting element derived from DCM can be manufactured.
[0194]
[Example 10]
In this example, in the organic light emitting device shown in FIG. 29B, a hole injection region made of a hole injection material is provided between the anode 2702 and the organic compound layer 2703 between the cathode 2704 and the organic compound layer. An example of an organic light emitting device in which an electron injection region made of an electron injection material is inserted and a triplet light emitting material is applied as a light emitting material will be specifically illustrated. The element structure is shown in FIG.
[0195]
First, a glass substrate on which ITO (anode) is formed by depositing ITO to a thickness of about 100 nm is prepared. The glass substrate having this ITO is carried into a vacuum chamber as shown in FIG. In this embodiment, seven types of materials (5 types are organic compounds and two types are inorganic materials that serve as a cathode) are vapor-deposited, so seven vapor deposition sources are required.
[0196]
First, CuPc, which is a hole injection material, is deposited to 20 nm, but the deposition of CuPc reaches 20 nm, and at the same time, deposition of α-NPD, which is a hole transport material, is deposited at 0.3 nm / s without any interval. Start with a rate. The reason for not leaving the interval is to prevent the formation of the impurity layer as described above.
[0197]
After forming a hole transport region consisting of only α-NPD to 30 nm, the deposition of BAlq, which is an electron transport material, is started at 0.3 nm / s while the deposition rate of α-NPD is fixed at 0.3 nm / s. That is, a mixed region (α-NPD + BAlq) in which the rate ratio of α-NPD and BAlq is 1: 1 is formed by co-evaporation.
[0198]
The mixed region is formed to 20 nm. At this time, the middle 10 nm in the mixed region (that is, between 5 nm to 15 nm in the mixed region 20 nm) is Ir (ppy) which is a triplet light emitting material. _Three Is added as a light emitting material. The ratio is BAlq: Ir (ppy) in weight ratio _Three = 50: 7.
[0199]
After the mixed region reaches 20 nm, α-NPD and Ir (ppy) _Three In this case, the deposition is completed, and only BAlq is continuously deposited to form the electron transport region. The thickness is 20 nm. At the same time as the deposition of BAlq is finished, without any interval, Alq, which is an electron injection material _Three Deposition of about 30 nm is started. The reason for not leaving the interval is to prevent the formation of the impurity layer as described above.
[0200]
Finally, LiF is deposited to about 1 nm and aluminum is deposited to about 150 nm to form a cathode and Ir (ppy) _Three A green light emitting triplet light emitting device derived from is obtained.
[0201]
[Example 11]
In this example, an element in which the present invention is applied to the triplet light emitting element as shown in FIG. 9 in the embodiment mode of the invention is specifically illustrated. The element structure is shown in FIG. In this embodiment, a vapor deposition source with a shutter as shown in FIG. 11 is used to form a concentration gradient (graph 1010 in FIG. 10).
[0202]
First, ITO is deposited on the glass substrate 1001 to a thickness of about 100 nm by sputtering to form an anode 1002. Next, a hole transporting mixed layer 1003 composed of CuPc as the hole injection material 1011 and α-NPD as the hole transport material 1012 is formed to a thickness of 40 nm. At this time, a density gradient as shown in graph 1010 is formed by opening and closing the shutter.
[0203]
Subsequently, while gradually reducing the deposition rate of α-NPD, deposition of 4,4′-N, N′-dicarbazole-biphenyl (hereinafter referred to as “CBP”) which is the host material 1013 of the triplet light emitting material By increasing the rate, a bipolar mixed layer 1004 having a concentration gradient composed of α-NPD and CBP is formed to 20 nm. Next, the blocking mixed layer 1005 having a concentration gradient composed of CBP and BCP is formed by increasing the deposition rate of BCP as the blocking material 1014 while decreasing the deposition rate of CBP. The film thickness is 10 nm.
[0204]
Since this embodiment is a triplet light emitting element, tris (2-phenylpyridine) iridium (hereinafter referred to as “Ir”) which is a triplet light emitting material 1016 is formed during the formation of the bipolar mixed layer 1004 and the blocking mixed layer 1005. (ppy) _Three Dope). The doped region 1008 is most suitable in the region where the concentration of CBP as the host material is high, that is, in the vicinity of the boundary between the bipolar mixed layer 1004 and the blocking mixed layer 1005. In this example, ± 5 nm of the boundary, a total of 10 nm is used as a doped region 1008 and 6 wt% is doped.
[0205]
Furthermore, the electron transporting mixed layer 1006 is made of BCP and Alq, which have a high electron transport capability. _Three Consists of. The concentration of BCP decreases with increasing distance from the anode. _Three On the contrary, a concentration gradient is formed so that the concentration of is increased. That is, in this case, BCP is a blocking material and electron transport material, Alq _Three Plays the role of electron injection material 1015. The film thickness of the electron transporting mixed layer 1006 is 40 nm.
[0206]
Finally, as the cathode 1007, an Al: Li alloy (Li is 0.5 wt% by weight) is deposited to a thickness of about 150 nm, so that Ir (ppy) _Three Thus, an organic light emitting device exhibiting green triplet emission derived from can be produced.
[0207]
[Example 12]
In this example, a light-emitting device including the organic light-emitting element disclosed in the present invention will be described. FIG. 12A is a sectional view of an active matrix light emitting device using the organic light emitting element of the present invention. Note that although a thin film transistor (hereinafter referred to as “TFT”) is used here as an active element, a MOS transistor may be used.
[0208]
Further, although a top gate TFT (specifically, a planar TFT) is exemplified as the TFT, a bottom gate TFT (typically an inverted staggered TFT) can also be used.
[0209]
In FIG. 12A, reference numeral 1201 denotes a substrate. Here, a substrate that transmits visible light is used. Specifically, a glass substrate, a quartz substrate, a crystallized glass substrate, or a plastic substrate (including a plastic film) may be used. Note that the substrate 1201 includes an insulating film provided on a surface thereof.
[0210]
A pixel portion 1211 and a driver circuit 1212 are provided over the substrate 1201. First, the pixel portion 1211 will be described.
[0211]
The pixel portion 1211 is an area for displaying an image. A plurality of pixels exist on the substrate, and each pixel has a TFT (hereinafter referred to as “current control TFT”) 1202 for controlling a current flowing through the organic light emitting element, a pixel electrode (anode) 1203, and an organic compound layer. 1204 and a cathode 1205 are provided. Although only the current control TFT is shown in FIG. 12A, a TFT (hereinafter referred to as “switching TFT”) for controlling the voltage applied to the gate of the current control TFT is provided.
[0212]
Here, the current control TFT 1202 is preferably a p-channel TFT. Although an n-channel TFT can be used, when a current control TFT is connected to the anode of the organic light emitting device as shown in FIG. 12A, the p-channel TFT can reduce power consumption. . However, the switching TFT may be an n-channel TFT or a p-channel TFT.
[0213]
Further, the pixel electrode 1203 is electrically connected to the drain of the current control TFT 1202. In this embodiment, since a conductive material having a work function of 4.5 to 5.5 eV is used as the material of the pixel electrode 1203, the pixel electrode 1203 functions as an anode of the organic light emitting element. As the pixel electrode 1203, typically, indium oxide, tin oxide, zinc oxide, or a compound thereof (ITO or the like) may be used. An organic compound layer 1204 is provided on the pixel electrode 1203.
[0214]
Further, a cathode 1205 is provided on the organic compound layer 1204. As a material for the cathode 1205, it is desirable to use a conductive material having a work function of 2.5 to 3.5 eV. As the cathode 1205, a conductive film containing an alkali metal element or alkalinity metal element, a conductive film containing aluminum, or a stack of aluminum or silver over the conductive film may be used.
[0215]
A layer including the pixel electrode 1203, the organic compound layer 1204, and the cathode 1205 is covered with a protective film 1206. The protective film 1206 is provided to protect the organic light emitting element from oxygen and water. As a material for the protective film 1206, silicon nitride, silicon nitride oxide, aluminum oxide, tantalum oxide, or carbon (specifically, diamond-like carbon) is used.
[0216]
Next, the drive circuit 1212 will be described. The driver circuit 1212 is an area for controlling the timing of signals (gate signal and data signal) transmitted to the pixel portion 1211, and is provided with a shift register, a buffer, a latch, an analog switch (transfer gate), or a level shifter. FIG. 12A shows a CMOS circuit including an n-channel TFT 1207 and a p-channel TFT 1208 as a basic unit of these circuits.
[0217]
The circuit configuration of the shift register, buffer, latch, analog switch (transfer gate) or level shifter may be a known one. In FIG. 12A, the pixel portion 1211 and the drive circuit 1212 are provided over the same substrate, but an IC or LSI can be electrically connected without providing the drive circuit 1212.
[0218]
In FIG. 12A, the pixel electrode (anode) 1203 is electrically connected to the current control TFT 1202, but a structure in which the cathode is connected to the current control TFT can also be adopted. In that case, the pixel electrode may be formed using the same material as the cathode 1205 and the cathode may be formed using the same material as the pixel electrode (anode) 1203. In that case, the current control TFT is preferably an n-channel TFT.
[0219]
Incidentally, the light emitting device shown in FIG. 12A is manufactured in the process of forming the wiring 1209 after the pixel electrode 1203 is formed. In this case, the pixel electrode 1203 may cause surface roughness. There is sex. Since the organic light-emitting element is a current-driven element, the characteristics may be deteriorated due to the surface roughness of the pixel electrode 1203.
[0220]
Therefore, as shown in FIG. 12B, a light emitting device in which the pixel electrode 1203 is formed after the wiring 1209 is formed is also conceivable. In this case, it is considered that the current injection property from the pixel electrode 1203 is improved as compared with the structure of FIG.
[0221]
In FIG. 12, each pixel provided in the pixel portion 1211 is separated by a positive taper bank-like structure 1210. By making this bank-like structure into, for example, a reverse taper type structure, it is possible to adopt a structure in which the bank-like structure does not contact the pixel electrode. An example is shown in FIG.
[0222]
In FIG. 34, a wiring and separation unit 3410 that also serves as a separation unit using wiring is provided. The shape of the wiring and separation part 3410 (structure with eaves) as shown in FIG. 34 is formed by laminating a metal constituting the wiring and a material (for example, metal nitride) having a lower etch rate than the metal, and etching. Can be formed. With this shape, a short circuit between the pixel electrode 3403 and the wiring and the cathode 3405 can be prevented. Note that in FIG. 34, unlike a normal active matrix light-emitting device, the cathode 3405 on the pixel has a stripe shape (similar to a passive matrix cathode).
[0223]
Here, FIG. 13 shows an appearance of the active matrix light-emitting device shown in FIG. 13A shows a top view, and FIG. 13B shows a cross-sectional view of FIG. 13A taken along PP ′. Further, the reference numerals in FIG. 12 are cited.
[0224]
In FIG. 13A, reference numeral 1301 denotes a pixel portion, 1302 denotes a gate signal side driving circuit, and 1303 denotes a data signal side driving circuit. Signals transmitted to the gate signal side drive circuit 1302 and the data signal side drive circuit 1303 are input from a TAB (Tape Automated Bonding) tape 1305 through the input wiring 1304. Although not shown, instead of the TAB tape 1305, a TCP (Tape Carrier Package) in which an IC (integrated circuit) is provided on the TAB tape may be connected.
[0225]
At this time, reference numeral 1306 denotes a cover material provided above the organic light emitting element shown in FIG. 12B, and is bonded by a sealing material 1307 made of resin. Any material may be used for the cover material 1306 as long as it does not transmit oxygen and water. In this embodiment, as shown in FIG. 13B, the cover material 1306 includes a plastic material 1306a and a carbon film (specifically, a diamond-like carbon film) 1306b provided on the front and back surfaces of the plastic material 1306a. 1306c.
[0226]
Further, as shown in FIG. 13B, the sealing material 1307 is covered with a sealing material 1308 made of resin so that the organic light emitting element is completely enclosed in the sealed space 1309. The sealed space 1309 may be filled with an inert gas (typically nitrogen gas or a rare gas), a resin, or an inert liquid (for example, liquid fluorinated carbon typified by perfluoroalkane). It is also effective to provide a hygroscopic agent or oxygen scavenger.
[0227]
Further, a polarizing plate may be provided on the display surface (the surface on which an image is observed) of the light emitting device shown in this embodiment. This polarizing plate has an effect of suppressing reflection of light incident from the outside and preventing an observer from being reflected on the display surface. Generally, a circularly polarizing plate is used. However, in order to prevent light emitted from the organic compound layer from being reflected by the polarizing plate and returning to the inside, it is preferable to adjust the refractive index so that the structure has less internal reflection.
[0228]
Note that any of the organic light-emitting elements disclosed in the present invention may be used as the organic light-emitting element included in the light-emitting device of this example.
[0229]
[Example 13]
In this embodiment, an active matrix light-emitting device is illustrated as an example of a light-emitting device including an organic light-emitting element disclosed in the present invention. Unlike Example 12, on the side opposite to a substrate on which an active element is formed. 1 shows a light emitting device having a structure for extracting light from a light source (hereinafter referred to as “upward emission”). FIG. 35 shows a cross-sectional view thereof.
[0230]
Note that although a thin film transistor (hereinafter referred to as “TFT”) is used here as an active element, a MOS transistor may be used. Further, although a top gate TFT (specifically, a planar TFT) is exemplified as the TFT, a bottom gate TFT (typically an inverted staggered TFT) can also be used.
[0231]
In this embodiment, the substrate 3501, the current control TFT 3502 formed in the pixel portion, and the drive circuit 3512 may have the same configuration as in the twelfth embodiment.
[0232]
The first electrode 3503 connected to the drain of the current control TFT 3502 is used as an anode in this embodiment. Therefore, it is preferable to use a conductive material having a higher work function. Typical examples include metals such as nickel, palladium, tungsten, gold, and silver. In this embodiment, it is preferable that the first electrode 3503 does not transmit light, but in addition, it is more preferable to use a material having high light reflectivity.
[0233]
An organic compound layer 3504 is provided on the first electrode 3503. Further, a second electrode 3505 is provided on the organic compound layer 3504, which is a cathode in this embodiment. In that case, it is desirable to use a conductive material having a work function of 2.5 to 3.5 eV as the material of the second electrode 3505. Typically, a conductive film containing an alkali metal element or alkalinity metal element, a conductive film containing aluminum, or a stack of aluminum or silver over the conductive film may be used. However, since this embodiment uses upward emission, it is a major premise that the second electrode 3505 is light transmissive. Therefore, when these metals are used, an ultrathin film of about 20 nm is preferable.
[0234]
In addition, a layer including the first electrode 3503, the organic compound layer 3504, and the second electrode 3505 is covered with a protective film 3506. The protective film 3506 is provided to protect the organic light emitting element from oxygen and water. In this embodiment, any material that transmits light may be used.
[0235]
In FIG. 35, the first electrode (anode) 3503 is electrically connected to the current control TFT 3502, but a structure in which the cathode is connected to the current control TFT can also be adopted. In that case, the first electrode may be formed of a cathode material and the second electrode may be formed of an anode material. At this time, the current control TFT is preferably an n-channel TFT.
[0236]
Further, reference numeral 3507 denotes a cover material, which is bonded by a sealing material 3508 made of resin. The cover material 3507 may be made of any material that does not transmit oxygen and water and that transmits light. In this embodiment, glass is used. The sealed space 3509 may be filled with an inert gas (typically nitrogen gas or a rare gas), a resin, or an inert liquid (for example, liquid fluorinated carbon typified by perfluoroalkane). It is also effective to provide a hygroscopic agent or oxygen scavenger.
[0237]
Signals transmitted to the gate signal side drive circuit and the data signal side drive circuit are input from a TAB (Tape Automated Bonding) tape 3514 through the input wiring 3513. Although not shown, instead of the TAB tape 3514, a TCP (Tape Carrier Package) in which an IC (integrated circuit) is provided on the TAB tape may be connected.
[0238]
Further, a polarizing plate may be provided on the display surface (the surface on which an image is observed) of the light emitting device shown in this embodiment. This polarizing plate has an effect of suppressing reflection of light incident from the outside and preventing an observer from being reflected on the display surface. Generally, a circularly polarizing plate is used. However, in order to prevent light emitted from the organic compound layer from being reflected by the polarizing plate and returning to the inside, it is preferable to adjust the refractive index so that the structure has less internal reflection.
[0239]
Note that any of the organic light-emitting elements disclosed in the present invention may be used as the organic light-emitting element included in the light-emitting device of this example.
[Example 14]
[0240]
In this example, a passive matrix light-emitting device is illustrated as an example of a light-emitting device including the organic light-emitting element disclosed in the present invention. FIG. 14 (a) shows a top view thereof, and FIG. 14 (b) shows a cross-sectional view of FIG. 14 (a) taken along PP ′.
[0241]
In FIG. 14A, reference numeral 1401 denotes a substrate, and here a plastic material is used. Plastic materials include polyimide, polyamide, acrylic resin, epoxy resin, PES (polyethylene sulfide), PC (polycarbonate), PET (polyethylene terephthalate) or PEN (polyethylene naphthalate) in plate form or on film Can be used.
[0242]
Reference numeral 1402 denotes a scanning line (anode) made of an oxide conductive film. In this embodiment, an oxide conductive film obtained by adding gallium oxide to zinc oxide is used. Reference numeral 1403 denotes a data line (cathode) made of a metal film. In this embodiment, a bismuth film is used. Reference numeral 1404 denotes a bank made of acrylic resin, which functions as a partition for dividing the data line 1403. Both the scanning lines 1402 and the data lines 1403 are formed in a plurality of stripes, and are provided so as to be orthogonal to each other. Although not shown in FIG. 14A, an organic compound layer is sandwiched between the scanning line 1402 and the data line 1403, and the intersection 1405 becomes a pixel.
[0243]
The scanning line 1402 and the data line 1403 are connected to an external drive circuit via the TAB tape 1407. Note that 1408 represents a wiring group formed by aggregating scanning lines 1402, and 1409 represents a wiring group formed by a set of connection wirings 1406 connected to the data line 1403. Further, although not shown, instead of the TAB tape 1407, a TCP provided with an IC on the TAB tape may be connected.
[0244]
14B, reference numeral 1410 denotes a sealing material, and reference numeral 1411 denotes a cover material bonded to the plastic material 1401 by the sealing material 1410. As the sealing material 1410, a photo-curing resin may be used, and a material with low degassing and low hygroscopicity is desirable. The cover material is preferably the same material as the substrate 1401, and glass (including quartz glass) or plastic can be used. Here, a plastic material is used.
[0245]
Next, an enlarged view of the structure of the pixel region is shown in FIG. Reference numeral 1413 denotes an organic compound layer. As shown in FIG. 14C, the bank 1404 has a shape in which the lower layer is narrower than the upper layer, and the data line 1403 can be physically divided. Further, the pixel portion 1414 surrounded by the sealing material 1410 has a structure in which the organic compound layer is prevented from being deteriorated by being blocked from the outside air by a sealing material 1415 made of resin.
[0246]
The light emitting device of the present invention having the above structure can be manufactured by a very simple process because the pixel portion 1414 is formed of the scanning lines 1402, the data lines 1403, the banks 1404, and the organic compound layer 1413. .
[0247]
Further, a polarizing plate may be provided on the display surface (the surface on which an image is observed) of the light emitting device shown in this embodiment. This polarizing plate has an effect of suppressing reflection of light incident from the outside and preventing an observer from being reflected on the display surface. Generally, a circularly polarizing plate is used. However, in order to prevent light emitted from the organic compound layer from being reflected by the polarizing plate and returning to the inside, it is preferable to adjust the refractive index so that the structure has less internal reflection.
[0248]
Note that any of the organic light-emitting elements disclosed in the present invention may be used as the organic light-emitting element included in the light-emitting device of this example.
[0249]
[Example 15]
In this embodiment, an example in which a printed wiring board is provided in the light emitting device shown in Embodiment 14 to form a module is shown.
[0250]
In the module shown in FIG. 15A, a TAB tape 1504 is attached to a substrate 1501 (here, including a pixel portion 1502, wirings 1503a and 1503b), and a printed wiring board 1505 is attached via the TAB tape 1504. Yes.
[0251]
Here, a functional block diagram of the printed wiring board 1505 is shown in FIG. Inside the printed wiring board 1505, at least ICs functioning as I / O ports (input or output units) 1506 and 1509, a data signal side drive circuit 1507, and a gate signal side circuit 1508 are provided.
[0252]
In this specification, a module having a configuration in which a TAB tape is attached to a substrate having a pixel portion formed on the substrate surface and a printed wiring plate having a function as a drive circuit is attached via the TAB tape is described in this specification. In particular, it will be called a drive circuit external module.
[0253]
Note that any of the organic light-emitting elements disclosed in the present invention may be used as the organic light-emitting element included in the light-emitting device of this example.
[0254]
[Example 16]
In this embodiment, an example in which a printed wiring board is provided in the light emitting device shown in Embodiment 12, 13 or 14 and modularized is shown.
[0255]
In the module shown in FIG. 16A, a TAB tape 1605 is attached to a substrate 1601 (including a pixel portion 1602, a data signal side driving circuit 1603, a gate signal side driving circuit 1604, wirings 1603a and 1604a). A printed wiring board 1606 is attached via a TAB tape 1605. A functional block diagram of the printed wiring board 1606 is shown in FIG.
[0256]
As shown in FIG. 16 (b), at least I / O ports 1607 and 1610 and an IC functioning as a control unit 1608 are provided inside the printed wiring board 1606. Although the memory unit 1609 is provided here, it is not always necessary. The control unit 1608 is a part having a function for controlling control of the driving circuit, correction of video data, and the like.
[0257]
A module having a configuration in which a printed wiring board having a function as a controller is attached to a substrate on which an organic light emitting element is formed is specifically referred to as a controller external module in this specification.
[0258]
Note that any of the organic light-emitting elements disclosed in the present invention may be used as the organic light-emitting element included in the light-emitting device of this example.
[0259]
[Example 17]
In this example, an example of a light-emitting device in which the triplet light-emitting element as shown in Examples 10 and 11 is driven by digital time gray scale display is shown. The light emitting device of this embodiment is very useful because it can achieve high luminous efficiency by utilizing light emission from a triplet excited state and at the same time can obtain a uniform image by digital time gradation display.
[0260]
A circuit configuration of a pixel using an organic light emitting element is shown in FIG. Tr represents a transistor, and Cs represents a storage capacitor. In the circuit configuration in FIG. 36 (a), the source line is connected to the source side of the transistor Tr1, and the gate line is connected to the gate of the transistor Tr1. The power supply line is connected to the storage capacitor Cs and the source side of the transistor Tr2. Since the anode of the organic light emitting element of the present invention is connected to the drain side of the transistor Tr2, the opposite side of the transistor Tr2 across the organic light emitting element is a cathode.
[0261]
In this circuit, when a gate line is selected, a current flows from the source line to Tr1, and a voltage corresponding to the signal is accumulated in Cs. And the voltage between the gate and source of Tr2 (V _gs The current controlled by) flows in Tr2 and the organic light emitting element.
[0262]
After Tr1 is selected, Tr1 is turned off and the Cs voltage (V _gs ) Is held. Therefore, V _gs It is possible to continue the current as much as depending on the current.
[0263]
FIG. 36B shows a chart for driving such a circuit by digital time gray scale display. That is, one frame is divided into a plurality of subframes, but in FIG. 36 (b), 6-bit gradation is used to divide one frame into six subframes (SF1 to SF6). TA is the write time. In this case, the ratio of each sub-frame light emission period is 32: 16: 8: 4: 2: 1 as shown in the figure.
[0264]
FIG. 36 (c) shows an outline of the TFT substrate drive circuit in this embodiment. In the substrate configuration in FIG. 36 (c), the power supply line and the cathode as shown in FIG. 36 (a) are connected to the pixel portion in which the organic light emitting device of the present invention is used as each pixel. The shift register is connected to the pixel portion in the order of shift register → latch 1 → latch 2 → pixel portion. A digital signal is input to the latch 1, and image data can be sent to the pixel portion by a latch pulse input to the latch 2.
[0265]
The gate driver and the source driver are provided on the same substrate. In this embodiment, since the pixel circuit and the driver are designed to be digitally driven, a uniform image can be obtained without being affected by variations in TFT characteristics.
[0266]
[Example 18]
In this embodiment, an example of an active matrix type constant current driving circuit which is driven by passing a constant current through the organic light emitting element disclosed in the present invention is shown. The circuit configuration is shown in FIG.
[0267]
A pixel 3710 illustrated in FIG. 37 includes a signal line Si, a first scanning line Gj, a second scanning line Pj, and a power supply line Vi. The pixel 3710 includes Tr1, Tr2, Tr3, Tr4, a mixed junction organic light emitting element 3711, and a storage capacitor 3712.
[0268]
The gates of Tr3 and Tr4 are both connected to the first scanning line Gj. One of the source and drain of Tr3 is connected to the signal line Si, and the other is connected to the source of Tr2. One of the source and drain of Tr4 is connected to the source of Tr2, and the other is connected to the gate of Tr1. That is, one of the source and drain of Tr3 and one of the source and drain of Tr4 are connected.
[0269]
The source of Tr1 is connected to the power supply line Vi, and the drain is connected to the source of Tr2. The gate of Tr2 is connected to the second scanning line Pj. The drain of Tr2 is connected to the pixel electrode of the organic light emitting element 3711. The organic light emitting element 3711 includes a pixel electrode, a counter electrode, and an organic compound layer provided between the pixel electrode and the counter electrode. A constant voltage is applied to the counter electrode of the organic light emitting element 3711 by a power source provided outside the light emitting panel.
[0270]
Note that Tr3 and Tr4 may be either n-channel TFTs or p-channel TFTs. However, Tr3 and Tr4 have the same polarity. Tr1 may be either an n-channel TFT or a p-channel TFT. Tr2 may be either an n-channel TFT or a p-channel TFT. One of the pixel electrode and the counter electrode of the organic light emitting device is an anode, and the other is a cathode. When Tr2 is a p-channel TFT, it is desirable to use the anode as the pixel electrode and the cathode as the counter electrode. Conversely, when Tr2 is an n-channel TFT, it is desirable to use the cathode as the pixel electrode and the anode as the counter electrode.
[0271]
The storage capacitor 3712 is formed between the gate and the source of Tr1. The storage capacitor 3712 is a voltage between the gate and the source of Tr1 (V _gs ) Is more reliably maintained, but is not necessarily provided.
[0272]
In the pixel shown in FIG. 37, the current supplied to the signal line Si is controlled by a current source included in the signal line driver circuit.
[0273]
By applying the circuit configuration as described above, it is possible to perform a constant current drive in which a constant current is supplied to the organic light emitting element to keep the luminance constant. Although the organic light emitting device having the mixed region disclosed in the present invention has a longer life than the conventional organic light emitting device, it is effective because the life can be further extended by performing constant current driving as described above. It is.
[0274]
[Example 19]
The light-emitting device of the present invention described in the above embodiment has an advantage of low power consumption and long life. Therefore, an electric appliance in which the light-emitting device is included as a display unit or the like is an electric appliance that can operate with lower power consumption than the conventional one and that can be maintained for a long time. In particular, an electric appliance such as a portable device that uses a battery as a power source is extremely useful because low power consumption is directly linked to convenience (battery is unlikely to run out).
[0275]
Further, since the light-emitting device is a self-luminous type, a backlight like a liquid crystal display device is not necessary, and the thickness of the organic compound layer is less than 1 μm, so that it can be thin and light. Therefore, an electric appliance in which the light emitting device is included as a display unit or the like is an electric appliance that is thinner and lighter than conventional ones. This is also extremely useful because it is directly connected to convenience (lightness and compactness when carrying), especially with respect to electric appliances such as portable devices. Furthermore, in general electrical appliances, there is no doubt that being thin (not bulky) is also useful from the viewpoint of transportation (capable of mass transportation) and installation (securement of space such as rooms).
[0276]
Note that since the light-emitting device is a self-luminous type, the light-emitting device is superior in visibility in a bright place as compared with a liquid crystal display device and has a wide viewing angle. Therefore, an electric appliance having the light-emitting device as a display portion has a great merit in terms of easy viewing.
[0277]
That is, the electric appliance using the light emitting device of the present invention is extremely useful because it has the advantages of low power consumption and long life in addition to the advantages of the conventional organic light emitting device such as thin and light weight and high visibility.
[0278]
In this embodiment, an electric appliance including the light emitting device of the present invention as a display portion is illustrated. Specific examples thereof are shown in FIGS. Note that any of the metal complexes disclosed in the present invention may be used for the organic light-emitting element included in the electric appliance of this example. In addition, any of the forms shown in FIGS. 12 to 16 and FIGS. 34 to 37 may be used as the form of the light emitting device included in the electric appliance of the present embodiment.
[0279]
FIG. 17A shows a display device using an organic light emitting element, which includes a housing 1701a, a support base 1702a, and a display portion 1703a. By manufacturing a display using the light-emitting device of the present invention as the display portion 1703a, a thin and light display that can be kept long can be realized. Therefore, transportation becomes simple, space saving during installation is possible, and the service life is also long.
[0280]
FIG. 17B shows a video camera, which includes a main body 1701b, a display portion 1702b, an audio input portion 1703b, operation switches 1704b, a battery 1705b, and an image receiving portion 1706b. By manufacturing a video camera using the light-emitting device of the present invention as the display portion 1702b, a lightweight video camera with low power consumption can be realized. Therefore, the consumption of the battery is reduced and the carrying becomes easy.
[0281]
FIG. 17C illustrates a digital camera, which includes a main body 1701c, a display portion 1702c, an eyepiece portion 1703c, and an operation switch 1704c. By manufacturing a digital camera using the light-emitting device of the present invention as the display portion 1702c, a lightweight digital camera with low power consumption can be realized. Therefore, the consumption of the battery is reduced and the carrying becomes easy.
[0282]
FIG. 17D shows an image reproducing device provided with a recording medium, which includes a main body 1701d, a recording medium (such as CD, LD, or DVD) 1702d, an operation switch 1703d, a display unit (A) 1704d, and a display unit (B) 1705d. including. The display unit (A) 1704d mainly displays image information, and the display unit (B) 1705d mainly displays character information. By producing the image reproducing device using the light emitting device of the present invention as the display unit (A) 1704d and the display unit (B) 1705d, the image reproducing device that is low in power consumption and lightweight and that is kept long. realizable. Note that the image reproducing device provided with the recording medium includes a CD reproducing device, a game machine, and the like.
[0283]
FIG. 17E illustrates a portable (mobile) computer, which includes a main body 1701e, a display portion 1702e, an image receiving portion 1703e, an operation switch 1704e, and a memory slot 1705e. By manufacturing a portable computer using the light-emitting device of the present invention as the display portion 1702e, a thin and light portable computer with low power consumption can be realized. Therefore, the consumption of the battery is reduced and the carrying becomes easy. The portable computer can record information on a recording medium in which flash memory or nonvolatile memory is integrated, and can reproduce the information.
[0284]
FIG. 17F shows a personal computer, which includes a main body 1701f, a housing 1702f, a display portion 1703f, and a keyboard 1704f. By manufacturing a personal computer using the light-emitting device of the present invention as the display portion 1703f, a thin and lightweight personal computer with low power consumption can be realized. In particular, when a portable application such as a notebook computer is required, it is a great advantage in terms of battery consumption and lightness.
[0285]
In addition, the electric appliances often display information distributed through an electronic communication line such as the Internet or wireless communication such as radio waves, and in particular, opportunities for displaying moving image information are increasing. The response speed of the organic light emitting device is very fast, and it is suitable for such moving image display.
[0286]
Next, FIG. 18A shows a mobile phone, which includes a main body 1801a, an audio output unit 1802a, an audio input unit 1803a, a display unit 1804a, an operation switch 1805a, and an antenna 1806a. By manufacturing a mobile phone using the light-emitting device of the present invention as the display portion 1804a, a thin and light mobile phone with low power consumption can be realized. Therefore, the battery consumption is reduced, the carrying becomes easier and the body can be made compact.
[0287]
FIG. 18B shows an audio device (specifically, an on-vehicle audio), which includes a main body 1801b, a display portion 1802b, and operation switches 1803b and 1804b. By manufacturing an acoustic device using the light-emitting device of the present invention as the display portion 1802b, a lightweight acoustic device with low power consumption can be realized. In the present embodiment, in-vehicle audio is shown as an example, but it may be used for home audio.
[0288]
In addition, in the electric appliances as shown in FIGS. 17 to 18, the light emission luminance is modulated according to the brightness of the use environment by further incorporating a light sensor and providing means for detecting the brightness of the use environment. It is effective to have such a function. The user can recognize the image or the character information without any problem if the brightness of 100 to 150 can be secured in the contrast ratio as compared with the brightness of the usage environment. That is, when the usage environment is bright, it is possible to increase the brightness of the image for easy viewing, and when the usage environment is dark, the brightness of the image can be suppressed to reduce power consumption.
[0289]
Various electric appliances using the light-emitting device of the present invention as a light source can be said to be very useful because they can operate with low power consumption and can be thin and light. Typically, an electrical appliance including the light-emitting device of the present invention as a light source such as a backlight or a front light of a liquid crystal display device or a light source of a lighting device can achieve low power consumption and be thin and lightweight.
[0290]
Accordingly, even when the display units of the electric appliances of FIGS. 17 to 18 shown in this embodiment are all liquid crystal displays, the electric appliances using the light emitting device of the present invention as the backlight or front light of the liquid crystal display. By producing a thin, lightweight electric appliance with low power consumption can be achieved.
[0291]
【The invention's effect】
By implementing the present invention, a light-emitting device with low power consumption and excellent lifetime can be obtained. Furthermore, by using such a light-emitting device for a light source or a display portion, it is possible to obtain an electric appliance that is bright and consumes little power and is kept long.
[Brief description of the drawings]
FIG. 1 shows the role of a hole injection layer.
FIG. 2 is a diagram showing a concentration gradient.
FIG. 3 is a diagram showing a concentration gradient.
FIG. 4 is a diagram showing a concentration gradient.
FIG. 5 shows a structure of an organic light emitting element.
FIG. 6 shows a structure of an organic light emitting element.
FIG. 7 shows a structure of an organic light emitting element.
FIG. 8 shows a structure of an organic light emitting element.
FIG. 9 shows a structure of an organic light emitting element.
FIG. 10 shows a structure of an organic light emitting element.
FIG. 11 shows a vapor deposition apparatus.
FIG 12 illustrates a cross-sectional structure of a light-emitting device.
FIGS. 13A and 13B illustrate a top structure and a cross-sectional structure of a light-emitting device. FIGS.
FIGS. 14A and 14B illustrate a top structure and a cross-sectional structure of a light-emitting device. FIGS.
FIG 15 illustrates a structure of a light-emitting device.
FIG 16 illustrates a structure of a light-emitting device.
FIG. 17 shows a specific example of an electric appliance.
FIG. 18 is a diagram showing a specific example of an electric appliance.
FIG. 19 shows an energy band diagram.
FIG. 20 is a diagram showing an energy band diagram.
FIG. 21 is a diagram illustrating a state of an organic compound layer.
FIG. 22 shows a vapor deposition apparatus.
FIG. 23 shows formation of an impurity layer.
FIG. 24 shows a structure of an organic light emitting element.
FIG. 25 is a diagram illustrating a state of an organic compound layer.
FIG. 26 shows a structure of an organic light emitting element.
FIG. 27 shows a structure of an organic light emitting element.
FIG. 28 is a diagram showing a density profile.
FIG. 29 shows a structure of an organic light emitting element.
FIG. 30 shows a structure of an organic light emitting element.
FIG. 31 shows a vapor deposition apparatus.
FIG. 32 shows a vapor deposition apparatus.
FIG. 33 shows a structure of an organic light emitting element.
FIG 34 illustrates a cross-sectional structure of a light-emitting device.
FIG 35 illustrates a cross-sectional structure of a light-emitting device.
FIG 36 illustrates a structure of a light-emitting device.
FIG 37 illustrates a structure of a light-emitting device.

Claims (14)

In a light emitting device including an organic light emitting element including an anode, a cathode, and an organic compound layer provided between the anode and the cathode, the organic compound layer includes a hole transport region formed of a hole transport material. An electron transport region made of an electron transport material, and the hole transport region is located closer to the anode than the electron transport region, and between the hole transport region and the electron transport region. In addition, a mixed region including both the hole transport material and the electron transport material is provided, and a light emitting region to which a light emitting material that emits light is added only at the center in the mixed region is provided ,
A blocking material having a large energy difference between the highest occupied molecular orbital and the lowest unoccupied molecular orbital compared to the hole transporting material and the electron transporting material is added to a part of the mixed region, and the light emission The region is located closer to the anode than the region to which the blocking material is added . In a light emitting device including an organic light emitting element comprising an anode, a cathode, a hole injection region provided in contact with the anode, and an organic compound layer provided between the hole injection region and the cathode, The organic compound layer includes a hole transport region made of a hole transport material and an electron transport region made of an electron transport material, and the hole transport region is located closer to the anode than the electron transport region. In addition, a mixed region including both the hole transport material and the electron transport material is provided between the hole transport region and the electron transport region, and emits light only at the center in the mixed region. A light emitting region to which a light emitting material is added is provided ,
A blocking material having a large energy difference between the highest occupied molecular orbital and the lowest unoccupied molecular orbital compared to the hole transporting material and the electron transporting material is added to a part of the mixed region, and the light emission The region is located closer to the anode than the region to which the blocking material is added . In a light-emitting device including an organic light-emitting element comprising: an anode; a cathode; an electron injection region provided in contact with the cathode; and an organic compound layer provided between the anode and the electron injection region. The compound layer includes a hole transport region made of a hole transport material, and an electron transport region made of an electron transport material, and the hole transport region is located on the anode side of the electron transport region, In addition, a light emitting material in which a mixed region including both the hole transport material and the electron transport material is provided between the hole transport region and the electron transport region, and emits light only at the center in the mixed region. A light emitting region to which is added ,
A blocking material having a large energy difference between the highest occupied molecular orbital and the lowest unoccupied molecular orbital compared to the hole transporting material and the electron transporting material is added to a part of the mixed region, and the light emission The region is located closer to the anode than the region to which the blocking material is added . An anode, a cathode, a hole injection region provided in contact with the anode, an electron injection region provided in contact with the cathode, and an organic provided between the hole injection region and the electron injection region In the light emitting device including the organic light emitting element, the organic compound layer includes a hole transport region made of a hole transport material and an electron transport region made of an electron transport material, and A hole transport region is located on the anode side of the electron transport region, and a mixed region including both the hole transport material and the electron transport material between the hole transport region and the electron transport region. Is provided, and a light emitting region to which a light emitting material that emits light is added only at the center in the mixed region is provided ,
A blocking material having a large energy difference between the highest occupied molecular orbital and the lowest unoccupied molecular orbital compared to the hole transporting material and the electron transporting material is added to a part of the mixed region, and the light emission The region is located closer to the anode than the region to which the blocking material is added . The light emitting device according to any one of claims 1 to 4, to the direction from the anode to the cathode, the concentration of the hole transporting material in the mixed region is reduced, the mixing zone A light-emitting device, wherein the concentration of the electron transport material is increased. In a light emitting device including an organic light emitting element including an anode, a cathode, and an organic compound layer provided between the anode and the cathode, the organic compound layer includes a hole transport region formed of a hole transport material. An electron transport region made of an electron transport material, and a mixed region containing the hole transport material and the electron transport material at a certain ratio between the hole transport region and the electron transport region. And a light emitting region to which a light emitting material that emits light is added is provided only in the center of the mixed region ,
A blocking material having a large energy difference between the highest occupied molecular orbital and the lowest unoccupied molecular orbital compared to the hole transporting material and the electron transporting material is added to a part of the mixed region, and the light emission The region is located closer to the anode than the region to which the blocking material is added . In a light emitting device including an organic light emitting element comprising an anode, a cathode, a hole injection region provided in contact with the anode, and an organic compound layer provided between the hole injection region and the cathode, The organic compound layer includes a hole transport region made of a hole transport material and an electron transport region made of an electron transport material, and the positive transport layer is between the hole transport region and the electron transport region. A mixed region including a hole transport material and the electron transport material at a certain ratio is formed, and a light emitting region to which a light emitting material that emits light is added is provided only in the center of the mixed region ,
A blocking material having a large energy difference between the highest occupied molecular orbital and the lowest unoccupied molecular orbital compared to the hole transporting material and the electron transporting material is added to a part of the mixed region, and the light emission The region is located closer to the anode than the region to which the blocking material is added . In a light-emitting device including an organic light-emitting element comprising: an anode; a cathode; an electron injection region provided in contact with the cathode; and an organic compound layer provided between the anode and the electron injection region. The compound layer includes a hole transport region made of a hole transport material and an electron transport region made of an electron transport material, and the hole transport is between the hole transport region and the electron transport region. A mixed region including a material and the electron transport material at a certain ratio is formed, and a light emitting region to which a light emitting material that emits light is added is provided only in the center of the mixed region ,
A blocking material having a large energy difference between the highest occupied molecular orbital and the lowest unoccupied molecular orbital compared to the hole transporting material and the electron transporting material is added to a part of the mixed region, and the light emission The region is located closer to the anode than the region to which the blocking material is added . An anode, a cathode, a hole injection region provided in contact with the anode, an electron injection region provided in contact with the cathode, and an organic provided between the hole injection region and the electron injection region In the light emitting device including the organic light emitting element, the organic compound layer includes a hole transport region made of a hole transport material and an electron transport region made of an electron transport material, and A mixed region containing the hole transport material and the electron transport material at a certain ratio is formed between the hole transport region and the electron transport region, and light is emitted only at the center in the mixed region. a light emitting region where the light emitting material is added exhibiting provided,
A blocking material having a large energy difference between the highest occupied molecular orbital and the lowest unoccupied molecular orbital compared to the hole transporting material and the electron transporting material is added to a part of the mixed region, and the light emission The region is located closer to the anode than the region to which the blocking material is added . The light emitting device according to any one of claims 1 to 9, relates to the mixing area, the percentage of the mass of the hole transporting material and hole transporting material to the total mass of the electron transport material A light emitting device characterized by being 10 percent or more and 90 percent or less. The light emitting device according to any one of claims 1 to 10, wherein the mixed region 10 nm or more, light emitting device which is a thickness of less than 100 nanometers. The light emitting device according to any one of claims 1 to 11, wherein the luminescent material, light emitting device, characterized in that exhibits light emission from a triplet excited state. The light emitting device according to any one of claims 1 to 12, wherein the light emitting material, the light emitting device, characterized in that the complex, of which central metal is iridium. An electrical appliance using the light emitting device according to any one of claims 1 to 13 .

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