CN101106180B - Image display system - Google Patents

Abstract

The present invention relates to an image display system. The image display system comprises an electroluminescent diode having a composite electrode structure, wherein the composite electrode structure comprises: a film layer having an alkali metal or alkaline earth metal compound, wherein the alkali metal or alkaline earth metal compound has a carbonyl group or fluorine; and a metal oxide layer or a semiconductor compound layer.

Description

Image display system

technical field

The invention relates to an image display system, in particular to an image display system with serial organic electroluminescent diodes.

Background technique

In recent years, with the advancement of electronic product development technology and its increasingly wide application, such as the advent of mobile phones, PDAs and notebook computers, the demand for flat-panel displays with smaller volume and power consumption characteristics compared with traditional displays Increasing day by day, become one of the most important electronic application products at present. Among flat-panel displays, organic electroluminescent devices will undoubtedly become the best choice for next-generation flat-panel displays due to their characteristics of self-luminescence, high brightness, wide viewing angle, high response speed, and easy fabrication.

Organic electroluminescent devices are light-emitting diodes that use organic layers as active layers, and have been gradually used in flat panel displays in recent years. The development of organic electroluminescent devices with high luminous efficiency and long service life is one of the main trends of flat panel display technology at present.

In recent years, in order to further increase the brightness of a single pixel of an organic electroluminescent device and achieve full colorization, a tandem organic electroluminescent device has been proposed in the industry. The tandem organic electroluminescence device, as its name implies, is to vertically stack a plurality of organic light emitting diodes (OLEDs), connect them in series, and drive them with a single power source.

Please refer to FIG. 1 , which shows a schematic diagram of a cross-sectional structure of a conventional tandem organic electroluminescent device 10 . The conventional tandem organic electroluminescent device 10 includes a first organic light emitting diode 20 and a second organic light emitting diode 30 stacked on the first organic light emitting diode 20, wherein the first organic light emitting diode 20 sequentially includes a first organic light emitting diode The electrode 21 , the first organic material layer 22 , and the connection electrode 23 , and the second organic light emitting diode 30 uses the connection electrode 23 as the bottom electrode, and includes the second organic material layer 32 and the second electrode 33 in sequence. It should be noted that the connection electrode 23 serves as the upper electrode of the first OLED 20 and as the lower electrode of the second OLED 30 .

In the research and development of tandem organic electroluminescent devices, the biggest challenge is how to develop an effective connection electrode structure, which is arranged between adjacent light-emitting units, so that the current can flow smoothly. without being hindered by the energy barrier of the substantial interface.

The structures and formation methods of conventional connecting electrodes are listed and discussed as follows:

Forrest, S.R. et al. (Science1997, 276, 2009; J.App.Phys.1999, 86, 4067; J.App.Phys.1999, 864076) first proposed the concept of tandem OLED's structure , which is used as the connecting electrode is ITO, and the method is to form an ITO electrode on the organic material layer of the first organic light emitting diode by sputtering after completing the organic material layer of the first organic light emitting diode, and then The organic material layer and the electrode layer of the second organic light emitting diode are formed on the ITO electrode. However, in the process of forming the ITO transparent conductive layer by sputtering, since the organic material layer as the under layer will be bombarded by the ions emitted by the target, the surface of the organic material layer will be oxidized, deteriorated, or the original The flatness is destroyed, thus increasing the energy barrier of the heterogeneous interface between the transparent cathode and the organic material layer, making it difficult for charge carriers to enter the organic material layer from the transparent cathode and accumulate at the interface, which will lead to device operation Voltage increases and device life decreases.

Howard, W.E.and Jones, G.W et al. (US Patent 6337492B1) used the composite structure of Mg:Ag/IZO as the connection electrode. After completing the organic material layer of the first organic light-emitting diode, the method was sputtered according to the method. The Mg:Ag electrode layer and the IZO electrode layer are formed sequentially, and then the organic material layer and the electrode layer of the second organic light emitting diode are formed on the IZO electrode. Howard uses the composite structure of Mg:Ag/IZO to facilitate the transport of charge carriers. However, since the connecting electrodes are still formed by sputtering, the organic material layer as the lining layer will still be damaged.

Kido, J et al. (SID03Digest2003, 34, 979) used Cs:Bphen/V ₂ O ₅ as the connection electrode structure, and the method was to use sputtering sequentially after completing the organic material layer of the first organic light-emitting diode. Forming the Cs:Bphen electrode layer and the V ₂ O ₅ electrode layer and then forming the organic material layer and the electrode layer of the second organic light emitting diode on the V ₂ O ₅ electrode. The obtained device has a device efficiency twice that of a single-layer device structure. However, the Cs and Bphen raw material costs are high, and the tandem OLED is not easy to mass-produce. In addition, Cs is easily oxidized during the evaporation process.

Tang, CW et al. (Appl. Phys. Lett. 2004, 84, 167) used Alq:Li (or TPBI:Li)/NPB:FeCl ₃ as the connection electrode structure, and the method was to complete the first organic light-emitting diode After the organic material layer, form an Alq:Li (or TPBI:Li) layer by vapor deposition, and then form an NPB: _FeCl electrode layer, and then form an organic material layer and an electrode layer of the second organic light-emitting diode on the NPB: FeCl ₃ electrode layer. The obtained device has a device efficiency twice that of a single-layer device structure. However, its disadvantages are that it is not easy to control the concentration during Li doping, and Li is easily oxidized to Li ₂ O during evaporation.

Chen, CH et al. (Jpn J.Appl.Phys.2004, 43, 6418) used Alq:Mg/WO ₃ as the connection electrode structure, which was done by vapor deposition after completing the organic material layer of the first organic light-emitting diode. Alq:Mg/WO ₃ is sequentially formed in the same way, and then the organic material layer and electrode layer of the second organic light-emitting diode are formed on WO ₃ , and the device efficiency is 4 times that of a single-layer device structure. But its disadvantage is that it will cause color shift.

Tsutsui, T et al. (Curr.Appl.Phys.2005, 5, 341) used Alq:Mg/V ₂ O ₅ as the connection electrode structure, which was done by sputtering after the organic material layer of the first organic light-emitting diode was completed. The Alq:Mg electrode layer and the V ₂ O ₅ electrode layer are sequentially formed in this manner, and then the organic material layer and the electrode layer of the second organic light emitting diode are formed on the V ₂ O ₅ electrode. The device efficiency of the obtained device is twice that of a single-layer device structure.

Kwok, H.S. et al. (Appl. Phys. Lett. 2005, 87, 093504) used LiF/Ca/Ag (or Au) as the connection electrode structure, and the method was to use The evaporation method forms LiF, Ca, and Ag electrode layers in sequence, and then forms the organic material layer and electrode layer of the second organic light emitting diode on the Ag electrode. The device efficiency of the obtained device is 1.9 times that of a single-layer device structure. However, its disadvantage is that Ca is extremely easily oxidized.

In view of this, developing a novel connecting electrode structure of the tandem organic electroluminescent device to overcome the problems caused by the conventional technology is an important subject of the current tandem organic electroluminescent device technology.

Contents of the invention

In view of this, the object of the present invention is to provide an image display system with organic electroluminescent diodes, which has a novel composite electrode structure (or connection electrode structure), which can increase the organic electroluminescent diode (or series electroluminescent The luminous efficiency of the light-emitting diode) and the situation of avoiding color shift (color shift) can be avoided, which meets the demand of the current flat-panel display market.

In order to achieve the object of the present invention, the preferred embodiment of the present invention provides an image display system, the image display system includes an electroluminescent diode, and the electroluminescent diode has a composite electrode structure, wherein the composite electrode structure includes: a film layer of a metal compound, wherein the alkali metal or alkaline earth metal compound has a carbonyl group or fluorine; and a metal oxide layer or a semiconductor compound layer.

In addition, according to another preferred embodiment of the present invention, the image display system includes a tandem electroluminescent diode, and the electroluminescent diode includes: a first electrode, a second electrode, a plurality of organic electroluminescent units, and at least one Connect the electrode structure. Wherein, the plurality of organic electroluminescent units are formed between the first electrode and the second electrode, and the connecting electrode structure is arranged between any two adjacent organic electroluminescent units. Wherein, the connection electrode structure includes: a film layer having an alkali metal or alkaline earth metal compound, wherein the alkali metal or alkaline earth metal compound has a carbonyl group or a fluorine group, and a metal oxide layer or a semiconductor compound layer.

In order to make the above-mentioned object and features of the present invention more obvious and easy to understand, the preferred embodiments are specifically cited below, and in conjunction with the accompanying drawings, the detailed description is as follows:

Description of drawings

FIG. 1 is a schematic diagram showing a cross-sectional structure of a conventional tandem organic electroluminescent device.

FIG. 2 is a schematic diagram showing a general organic electroluminescent diode including a composite electrode structure according to a preferred embodiment of the present invention.

Figure 3 shows the series-connected electroluminescent diodes according to the preferred embodiment of the present invention.

FIG. 4 shows a series-connected electroluminescent diode according to another preferred embodiment of the present invention.

5 is a graph showing the relationship between the operating voltage and the current density of the electroluminescent diodes described in Examples 1-4 and Comparative Example 1 of the present invention.

6 is a graph showing the relationship between current density and luminance of the electroluminescent diodes described in Examples 1 to 4 and Comparative Example 1 of the present invention.

7 is a graph showing the relationship between the current density and luminous efficiency of the electroluminescent diodes described in Examples 1 to 4 and Comparative Example 1 of the present invention.

8 is a graph showing the relationship between the operating voltage and the current density of the electroluminescent diodes described in Examples 5-7 and Comparative Example 2 of the present invention.

9 is a graph showing the relationship between current density and luminance of the electroluminescent diodes described in Examples 5 to 7 and Comparative Example 2 of the present invention.

10 is a graph showing the relationship between the current density and the luminous efficiency of the electroluminescent diodes described in Examples 5 to 7 and Comparative Example 2 of the present invention.

11 is a graph showing the relationship between the intensity and the emission wavelength of the electroluminescent diodes described in Examples 5 to 7 and Comparative Example 2 of the present invention.

FIG. 12 is a schematic diagram showing the structure of an image display system according to the present invention.

【Description of main device symbols】

Conventional tandem organic electroluminescent device ~ 10; first organic light emitting diode ~ 20; second organic light emitting diode ~ 30; first electrode ~ 21; first organic material layer ~ 22; connecting electrode ~ 23; second organic material Layer ~ 32; second electrode ~ 33; general organic electroluminescent diode (single light-emitting unit structure) ~ 100; substrate ~ 110; anode ~ 120; organic electroluminescent unit ~ 130; light-emitting layer ~ 131; hole injection layer ~132; hole transport layer ~133; electron transport layer ~134; electron injection layer ~135; composite electrode structure ~140; film layer with alkali metal or alkaline earth metal compound ~142; metal oxide layer or semiconductor compound layer ~ 144; serial electroluminescent diode ~ 200; substrate ~ 210; anode ~ 220; first organic electroluminescent unit ~ 230; light emitting layer ~ 231; hole injection layer ~ 232; hole transport layer ~ 233; electron transport layer~234; electron injection layer~235; connecting electrode structure~240; film layer~242 with alkali metal or alkaline earth metal compound; metal oxide layer or semiconductor compound layer~244; metal layer~246; Light emitting unit ~ 250; cathode ~ 260; series electroluminescent diode ~ 300.

Detailed ways

The present invention provides a novel composite electrode structure, which can be used as the cathode electrode or anode electrode of a general organic electroluminescent diode (single light-emitting unit structure), or the connection electrode structure of a series organic electroluminescent diode, which can increase the The luminous efficiency of electroluminescent diodes (or series electroluminescent diodes) can be improved, and the situation of color shift can be avoided.

Please refer to FIG. 2 , which shows a general organic electroluminescent diode (single light-emitting unit structure) 100 using the composite electrode structure of the present invention as a cathode. The organic electroluminescent device 100 with a single light-emitting unit structure includes a substrate 110 , such as a glass, ceramic, plastic substrate or semiconductor substrate. The substrate can be selected as required, that is, if a top-emission organic electroluminescent device is to be formed, the substrate can also be an opaque substrate; For a light emitting device, the substrate may be a transparent substrate. The anode 120 is formed on the upper surface of the substrate 110 . The anode can be a transparent electrode, a metal electrode or a composite electrode, and its material can be selected from lithium, magnesium, calcium, aluminum, silver, indium, gold, tungsten, nickel, platinum, alloys formed of the above elements, indium tin oxide, etc. (ITO), Indium Zinc Oxide (IZO), Zinc Aluminum Oxide (AZO), Zinc Oxide (ZnO) or a combination thereof, which can be formed by thermal evaporation, sputtering or plasma enhanced chemical vapor deposition .

Next, an organic electroluminescence unit 130 is formed on the anode 120 . The organic electroluminescent unit 130 includes at least a light emitting layer 131 (light emitting layer), and may further include a hole injection layer 132 , a hole transport layer 133 , an electron transport layer 134 , and an electron injection layer 135 . Each film layer of the organic electroluminescent unit 130 can be a small molecule organic electroluminescent material or a polymer organic electroluminescent material. If it is a small molecule organic light emitting diode material, the organic light emitting diode material can be formed by vacuum evaporation. layer; if it is a polymer organic light emitting diode material, the organic light emitting diode material layer can be formed by spin coating, inkjet or screen printing. In addition, the light-emitting layer 131 may include organic electroluminescent materials and dopant, and those skilled in the art may change the content of the matched dopant depending on the organic electroluminescent material used and the required device characteristics. Doping amount. Therefore, the doping amount of the dopant is not a characteristic of the present invention, nor is it a basis for limiting the scope of the present invention. The dopant can be an energy transfer dopant material or a carrier trapping dopant material, and the dopant helps to suppress the concentration extinction phenomenon of the organic electroluminescent material , and make the device obtain high efficiency and high brightness. The organic electroluminescence material can be a fluorescence light-emitting material. However, in some preferred embodiments of the present invention, the organic electroluminescent material can also be a phosphorescence luminescent material.

Referring to FIG. 2 , the compound electrode structure 140 of the present invention is disposed on the organic electroluminescent unit 130 , and serves as the cathode of the general organic electroluminescent diode (single light emitting unit structure) 100 in this embodiment.

According to a preferred embodiment of the present invention, the composite electrode structure 140 for an electroluminescent diode includes a film layer 142 of an alkali metal or alkaline earth metal compound, and a metal oxide layer or a semiconductor compound layer 144 . Wherein, the alkali metal or alkaline earth metal compound has a carbonyl group or fluorine. The alkali metal or alkaline earth metal compound can be a fluoride containing Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr, or Ba. In a series of embodiments of the present invention, the alkali metal or alkaline earth The metal compound is NaF, KF, RbF, CsF, BeF ₂ , MgF ₂ , CaF ₂ , SrF ₂ , or BaF ₂ . The alkali metal or alkaline earth metal compound can be a carbonyl compound containing Na, K, Rb, Cs, Be, Mg, Ca, Sr, or Ba. In a series of embodiments of the present invention, the alkali metal or alkaline earth metal compound Li ₂ CO ₃ , LiCO ₃ , Na ₂ CO ₃ , NaCO ₃ , K ₂ CO ₃ , KCO ₃ , Rb ₂ CO ₃ , RbCO ₃ , Cs ₂ CO ₃ , CsCO ₃ , BeCO, BeCO ₃ , MgCO, MgCO ₃ , CaO, Ca ₂ CO ₃ , CaCO ₃ , SrCO, SrCO ₃ , BaCO or BaCO ₃ . It is worth noting that the film layer with alkali metal or alkaline earth metal compound can be further doped with an electron transport material (electron transport material), and the electron transport material can be any conventional electron transport material, such as Alq ₃ , BeBq _2. TPBI, PBD, or TAZ.

The metal oxide layer includes a transition metal oxide, wherein the transition metal oxide is an oxide of a Group IB, Group IIB, Group IVB, Group VB, or Group VIIIB metal, an oxide of Cr, or an oxide of W. It is preferably an oxide of V or W. In a series of embodiments of the present invention, the metal oxide layer may include WO, W ₂ O ₃ , WO ₂ , WO ₃ , W ₂ O ₅ , VO, V ₂ O ₃ , VO ₂ , or V ₂ O ₅ .

The semiconductor compound layer includes a semiconductor layer of Si, Ge, GaAs, SiC, or SiGe. According to a preferred embodiment of the present invention, the semiconductor compound layer is an undoped semiconductor compound layer. In addition, according to another preferred embodiment of the present invention, the semiconductor compound layer is a semiconductor compound layer doped with P-type elements or N-type elements, wherein the P-type elements can be, for example, boron, and the N-type elements can be, for example, phosphorus, arsenic , or antimony.

Please refer to FIG. 3 , which shows a tandem electroluminescent diode 200 according to a preferred embodiment of the present invention. Here, a tandem electroluminescent diode with two organic electroluminescent units is taken as an example. According to the spirit of the present invention, the tandem electroluminescent diode 200 of the present invention may also include more than two organic electroluminescent units. The tandem electroluminescent diode 200 includes a substrate 210 , such as a glass, ceramic, plastic substrate or semiconductor substrate. The substrate 210 can be selected as required, that is, if a top-emission organic electroluminescent device is to be formed, the substrate can also be an opaque substrate; Luminescent devices, the substrate can be a transparent substrate. The anode 220 is formed on the upper surface of the substrate 210 . The anode can be a transparent electrode, a metal electrode or a composite electrode, and its material can be, for example, selected from lithium, magnesium, calcium, aluminum, silver, indium, gold, tungsten, nickel, platinum, alloys formed of the above elements, indium tin Oxide (ITO), Indium Zinc Oxide (IZO), Zinc Aluminum Oxide (AZO), Zinc Oxide (ZnO) or combinations thereof, which can be formed by thermal evaporation, sputtering or plasma enhanced chemical vapor deposition Way.

Next, the first organic electroluminescent unit 230 is formed on the anode 220 . The organic electroluminescent unit 230 includes at least a light emitting layer 231 (light emitting layer), and may further include a hole injection layer 232 , a hole transport layer 233 , an electron transport layer 234 , and an electron injection layer 235 . Each film layer of the first organic electroluminescent unit 230 can be a small molecule organic electroluminescent material or a polymer organic electroluminescent material. If it is a small molecule organic light emitting diode material, it can be formed by vacuum evaporation. Diode material layer; if it is a polymer organic light emitting diode material, the organic light emitting diode material layer can be formed by spin coating, inkjet or screen printing. In addition, the light-emitting layer 231 may include organic electroluminescent materials and dopants, and those skilled in the art may change the properties of the matched dopants depending on the organic electroluminescent materials used and the required device characteristics. Doping amount. Therefore, the doping amount of the dopant is not an essential feature of the present invention, nor is it a basis for limiting the scope of the present invention. The dopant can be an energy transfer (energy transfer) type dopant material or a carrier trapping (carriertrapping) type dopant material, and the dopant helps to suppress the concentration extinction phenomenon of the organic electroluminescent material, And make the device obtain high efficiency and high brightness. The organic electroluminescence material can be a fluorescence light-emitting material. However, in some preferred embodiments of the present invention, the organic electroluminescent material can also be a phosphorescence luminescent material.

Still referring to FIG. 3 , the connection electrode structure 240 is disposed on the first organic electroluminescence unit 230 . Wherein, the connection electrode structure 240 for the tandem electroluminescent diode 200 includes a film layer 242 having an alkali metal or alkaline earth metal compound, and a metal oxide layer or a semiconductor compound layer 244 . Wherein, the alkali metal or alkaline earth metal compound has a carbonyl group or fluorine. The alkali metal or alkaline earth metal compound can be a fluoride containing Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr, or Ba. In a series of embodiments of the present invention, the alkali metal or alkaline earth The metal compound is NaF, KF, RbF, CsF, BeF ₂ , MgF ₂ , CaF ₂ , SrF ₂ , or BaF ₂ . The alkali metal or alkaline earth metal compound can be a carbonyl compound containing Na, K, Rb, Cs, Be, Mg, Ca, Sr, or Ba. In a series of embodiments of the present invention, the alkali metal or alkaline earth metal Compounds are Li ₂ CO ₃ , LiCO ₃ , Na ₂ CO ₃ , NaCO ₃ , K ₂ CO ₃ , KCO ₃ , Rb ₂ CO ₃ , RbCO ₃ , Cs ₂ CO ₃ , CsCO ₃ , BeCO, BeCO ₃ , MgCO, MgCO _3. CaO, Ca ₂ CO ₃ , CaCO ₃ , SrCO, SrCO ₃ , BaCO or BaCO ₃ .

It is worth noting that the film layer with alkali metal or alkaline earth metal compound can be further doped with an electron transport material (electron transport material), and the electron transport material can be any conventional electron transport material, such as Alq ₃ , BeBq _2. TPBI, PBD, or TAZ.

The metal oxide layer includes a transition metal oxide, wherein the transition metal oxide is an oxide of a Group IB, Group IIB, Group IVB, Group VB, or Group VIIIB metal, an oxide of Cr, or an oxide of W. It is preferably an oxide of V or W. In a series of embodiments of the present invention, the metal oxide layer may include WO, W ₂ O ₃ , WO ₂ , WO ₃ , W ₂ O ₅ , VO, V ₂ O ₃ , VO ₂ , or V ₂ O ₅ .

The semiconductor compound layer includes a semiconductor layer of Si, Ge, GaAs, SiC, or SiGe. According to a preferred embodiment of the present invention, the semiconductor compound layer is an undoped semiconductor compound layer. In addition, according to another preferred embodiment of the present invention, the semiconductor compound layer is a semiconductor compound layer doped with P-type elements or N-type elements, wherein the P-type elements can be, for example, boron, and the N-type elements can be, for example, phosphorus, arsenic , or antimony.

Next, the second organic electroluminescence unit 250 is formed on the connection electrode structure 240 . The second organic electroluminescence unit 250 includes at least a light emitting layer 231 (light emitting layer), and may further include a hole injection layer 232 , a hole transport layer 233 , an electron transport layer 234 , and an electron injection layer 235 . Finally, a cathode 260 is formed on the second organic electroluminescence unit 250 . It is worth noting that the plurality of organic electroluminescent units can have excitation light of the same light color, for example, red, blue, and green light; in addition, the plurality of organic electroluminescent units can also have excitation light of different light colors. , so that the series electroluminescent diode emits white light.

In addition, according to another preferred embodiment of the present invention, the composite electrode structure or the connecting electrode structure may further include a metal layer. Please refer to FIG. 4, which is a tandem electroluminescent diode 300 according to a preferred embodiment of the present invention. The connection electrode structure 240 also includes a metal layer 246, which is arranged on the film layer 242 having an alkali metal or alkaline earth metal compound. 244 between the metal oxide layer or the semiconductor compound layer. Wherein, the metal layer 246 includes Al, Ag, Au, or alloys thereof.

The actual composition of each layer of the organic electroluminescent device according to the present invention and the advantages of the present invention are described below through Example 1, Example 2 and Comparative Example 1.

Fabrication of monochromatic electroluminescent diodes

Comparative Example 1:

A 100-nm-thick glass substrate having an ITO transparent electrode (anode) was cleaned by ultrasonic vibration using a neutral detergent, acetone, and ethanol. The substrate was blown dry with nitrogen and further cleaned with UV/ozone. Then, under a pressure of 10 ⁻⁵ Pa, a hole injection layer, a hole transport layer, an electron transport layer and light-emitting layer, an electron injection layer, and a metal electrode are sequentially deposited on the ITO electrode to obtain the electroluminescent device (1 ). The material and thickness of each layer are listed below.

Hole injection layer: the thickness is 20 nm, and the material is PEDT/PSS (poly(3,4-ethylenedioxythiophene) poly(styrenesulfonic acid) water-soluble dispersion).

Hole transport layer: thickness is 40nm, material is NPB (N, N'-di-1-naphthyl-N, N'-diphenyl-1,1'-biphenyl-1,1'-biphenyl base-4,4'-diamine).

Electron transport layer and light-emitting layer: the thickness is 60nm, the material is Alq ₃ (tris(8-quinolinol)aluminum), the light color is yellow-green, λmax=540nm.

Electron injection layer: the thickness is 1 nm, and the material is Cs ₂ CO ₃ .

Metal electrode: the thickness is 100nm, and the material is Al.

Then, the optical characteristics of the electroluminescent device (1) were measured with PR650 and Minolta LS110. Please refer to FIG. 5, which shows the relationship between the operating voltage and current density of the electroluminescent device (1); FIG. 6 shows the relationship between current density and brightness; in addition, FIG. 7 shows the relationship between current density and luminous efficiency.

Example 1

A 100-nm-thick glass substrate having an ITO transparent electrode (anode) was cleaned by ultrasonic vibration using a neutral detergent, acetone, and ethanol. The substrate was blown dry with nitrogen and further cleaned with UV/ozone. Then, under a pressure of 10 ^-5 Pa, the hole injection layer, the first hole transport layer, the electron transport layer and the first light-emitting layer, the connection electrode structure, the second hole transport layer, the electron transport layer and the second A light-emitting layer, an electron injection layer, and a metal electrode are placed on the ITO electrode to obtain the electroluminescent device (2). The material and thickness of each layer are listed below.

Hole injection layer: the thickness is 20 nm, and the material is PEDT/PSS (poly(3,4-ethylenedioxythiophene) poly(styrenesulfonic acid) water-soluble dispersion).

The first hole transport layer: the thickness is 40nm, the material is NPB (N, N'-di-1-naphthyl-N, N'-diphenyl-1,1'-biphenyl-1,1'- biphenyl-4,4'-diamine).

Electron transport layer and first light-emitting layer: the thickness is 40nm, the material is Alq ₃ (tris(8-hydroxyquinoline)aluminum), the light color is yellow-green, λmax=540nm.

Connection electrode structure: the connection electrode structure sequentially includes a film layer with an alkali metal or alkaline earth metal compound, a metal layer and a metal oxide layer. Wherein, the thickness of the film layer with alkali metal or alkaline earth metal compound is 20nm, and the material is Alq ₃ layer doped with Cs ₂ CO ₃ , wherein the weight ratio of Cs ₂ CO ₃ and Alq ₃ is 1:4. The thickness of the metal layer is 5 nm, and the material is Al. In addition, the thickness of the metal oxide layer is 5 nm, and the material is MoO ₃ .

The second hole transport layer: the thickness is 40nm, the material is NPB (N,N'-di-1-naphthyl-N,N'-diphenyl-1,1'-biphenyl-1,1'- biphenyl-4,4'-diamine).

Electron transport layer and second light-emitting layer: the thickness is 60nm, the material is Alq ₃ (tris(8-hydroxyquinoline)aluminum), the light color is yellow-green, λmax=540nm.

Electron injection layer: the thickness is 1 nm, and the material is CsCO ₃ .

Metal electrode: the thickness is 100nm, and the material is Al.

Then, the optical characteristics of the electroluminescent device (2) were measured with PR650 and Minolta LS110. Please refer to FIG. 5, which shows the relationship between the operating voltage and current density of the electroluminescent device (2); FIG. 6 shows the relationship between current density and brightness; in addition, FIG. 7 shows the relationship between current density and luminous efficiency.

Embodiment 2～4:

The electroluminescence device (3) described in embodiment 2 is the same as embodiment 1 except that the thickness of the metal layer is adjusted to 1 nm.

The electroluminescence device (4) described in embodiment 3 is the same as embodiment 2 except that the material of the metal layer is changed to Ag.

The electroluminescence device (5) described in Example 4 is the same as that of Example 1 except that the metal layer is removed.

Please refer to Figures 5-7, which are a series of photoelectric characteristic comparisons of Comparative Example 1 and Examples 1-4. As shown in the figure, brightness (brightness, at 20mA/cm ² ): electroluminescent device (2~4) (3000cd/m ² )>electroluminescent device (5) (1200cd/m ² )>electroluminescent device Device (1) (700cd/m ² ); luminous efficiency (efficiency, at 20mA/cm ² ): electroluminescent device (2 and 4) (8.3cd/A) > electroluminescent device (3) (～8cd /A)>Electroluminescent device (5) (5.8cd/A)>Electroluminescent device (1) (3.8cd/A).

Fabrication of White Light Emitting Diodes

Comparative Example 2:

A 100-nm-thick glass substrate having an ITO transparent electrode (anode) was cleaned by ultrasonic vibration using a neutral detergent, acetone, and ethanol. The substrate was blown dry with nitrogen and further cleaned with UV/ozone. Then, a hole injection layer, a hole transport layer, a blue light emitting layer, a red light emitting layer, an electron transport layer, an electron injection layer, and a metal electrode are sequentially deposited on the ITO electrode under a pressure of 10 ⁻⁵ Pa to obtain the Electroluminescence device (6). The material and thickness of each layer are listed below.

Hole injection layer: the thickness is 60nm, and the material is HI-406, a triphenylamine derivative produced by Idemitsu).

Hole transport layer: the thickness is 20 nm, and the material is HT-302, a triphenylamine derivative produced by Idemitsu Kogyo.

Blue light-emitting layer: the thickness is 10nm, and the material is a BH-01 layer (anthracene (anthence) derivative produced by Idemitsu Kogyo) doped with BD-04 (anthracene (anthence) derivative produced by Idemitsu Kogyo), wherein the The weight ratio of BD-04 to BH-01 is 2.5:97.5.

Red light-emitting layer: the thickness is 25nm, and the material is BH-01 layer (anthracene derivative produced by Idemitsu Kosho) doped with RD-01 (anthracene derivative produced by Idemitsu Kosho, where the RD-01 and BH-01 The weight ratio is 2.68:97.32.

Electron transport layer: the thickness is 10 nm, and the material is Alq ₃ (tris(8-hydroxyquinoline)aluminum).

Electron injection layer: the thickness is 0.7nm, and the material is LiF.

Metal electrode: the thickness is 100nm, and the material is Al.

Next, measure the optical characteristic of this electroluminescent device (6) with PR650 and Minolta LS110. Please refer to FIG. 8, which shows the relationship between the operating voltage and current density of the electroluminescent device (6); FIG. 9 shows the relationship between current density and brightness; in addition, FIG. 10 shows the relationship between current density and luminous efficiency.

Example 5

A 100-nm-thick glass substrate having an ITO transparent electrode (anode) was cleaned by ultrasonic vibration using a neutral detergent, acetone, and ethanol. The substrate was blown dry with nitrogen and further cleaned with UV/ozone. Next, the first hole injection layer, the first hole transport layer, the first blue light-emitting layer, the first red light-emitting layer, the first electron transport layer ^, the connection electrode structure, the first Two hole injection layers, a second hole transport layer, a second blue light emitting layer, a second red light emitting layer, a second electron transport layer, an electron injection layer, and a metal electrode are placed on the ITO electrode to obtain the electroluminescence device (7). The material and thickness of each layer are listed below.

The first hole injection layer: the thickness is 60nm, and the material is HI-406.

The first hole transport layer: the thickness is 20nm, and the material is HT-302.

The first blue light-emitting layer: the thickness is 10 nm, and the material is BH-01 layer doped with BD-04, wherein the weight ratio of BD-04 and BH-01 is 2.5:97.5.

The first red light-emitting layer: the thickness is 25 nm, and the material is a BH-01 layer doped with RD-01, wherein the weight ratio of RD-01 and BH-01 is 2.68:97.32.

The first electron transport layer: the thickness is 10 nm, and the material is Alq ₃ (tris(8-hydroxyquinoline)aluminum).

Connection electrode structure: the connection electrode structure sequentially includes a film layer with an alkali metal or alkaline earth metal compound, a metal layer and a metal oxide layer. Wherein, the thickness of the film layer with alkali metal or alkaline earth metal compound is 20nm, and the material is Alq ₃ layer doped with Cs ₂ CO ₃ , wherein the weight ratio of Cs ₂ CO ₃ and Alq ₃ is 1:4%. The thickness of the metal layer is 1 nm, and the material is Al. In addition, the thickness of the metal oxide layer is 5 nm, and the material is MoO ₃ .

The second hole injection layer: the thickness is 50nm, and the material is HI-406.

The second hole transport layer: the thickness is 20nm, and the material is HT-302.

The second blue light-emitting layer: the thickness is 10 nm, and the material is the BH-01 layer doped with BH-04, wherein the weight ratio of the BH-04 and BH-01 is 2.5:97.5.

The second red light-emitting layer: the thickness is 25 nm, and the material is a BH-01 layer doped with RH-01, wherein the weight ratio of RH-01 and BH-01 is 2.68:97.32.

The second electron transport layer: the thickness is 25 nm, and the material is Alq ₃ (tris(8-hydroxyquinoline)aluminum).

Electron injection layer: the thickness is 1 nm, and the material is Cs ₂ CO ₃ .

Metal electrode: the thickness is 100nm, and the material is Al.

Then, measure the optical characteristic of this electroluminescent device (7) with PR650 and Minolta LS110. Please refer to FIG. 8, which shows the relationship between the operating voltage and current density of the electroluminescent device (7); FIG. 9 shows the relationship between current density and brightness; in addition, FIG. 10 shows the relationship between current density and luminous efficiency.

Embodiment 6～7:

The electroluminescent devices (8) and (9) described in Examples 6 and 7 are the same as in Example 5 except that the thickness of the second hole injection layer is adjusted to 55 nm and 60 nm, respectively.

Please refer to Figures 8-10 for a series of photoelectric characteristic comparisons between Example 2 and Examples 5-7. As shown in the figure, brightness (brightness, at 20mA/cm2): electroluminescent device (7~9) (3600cd/m2) > electroluminescent device (6) (1500cd/m2); luminous efficiency (efficiency, at 20mA/cm2): electroluminescent device (9) (17.5cd/A) > electroluminescent device (7) (16.9cd/A) > electroluminescent device (8) (16.6cd/A) > electroluminescent device Lighting device (6) (8.3 cd/A). In addition, please refer to FIG. 11. It is worth noting that the maximum emission wavelength (λ _max ) of the luminescence spectrum obtained by the electroluminescent device (7-9) is the same as that of the single-layer device, and there is no color shift (color shift) occur.

Please refer to FIG. 12 , which shows a schematic structural diagram of an image display system including an electroluminescent device according to the present invention, wherein the image display system 600 including an electroluminescent device includes a display panel 400, and the display panel has the image display system described in the present invention. An active organic electroluminescent device (such as the electroluminescent diode 100 , 200 , or 300 shown in FIG. 2 , FIG. 3 , or FIG. 4 ), and the display panel 400 can be, for example, an organic electroluminescent diode panel. Still referring to FIG. 5 , the display panel 400 can be a part of an electronic device (such as the image display system 600 shown in the figure). Generally speaking, the image display system 600 includes a display panel 400 and an input unit 500 connected to the display panel, wherein the input unit transmits signals to the display panel to make the display panel display images. The image display system 600 can be, for example, a mobile phone, a digital camera, a PDA (Personal Data Assistant), a notebook computer, a desktop computer, a television, a car monitor, or a portable DVD player.

Although the present invention has been described above with preferred embodiments, it is not intended to limit the present invention. Any skilled person in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the present invention The scope of protection should be defined by the appended claims.

Claims (15)

1. An image display system, comprising: An electroluminescent diode having a composite electrode structure, wherein the composite electrode structure comprises: a film layer having an alkali metal or alkaline earth metal compound, wherein the alkali metal or alkaline earth metal compound has a carbonyl group or fluorine; and A transition metal oxide or semiconductor compound layer, wherein the transition metal oxide is an oxide of a Group IB, Group IIB, Group IVB, Group VB, or Group VIIIB metal, an oxide of Cr, or an oxide of W. 2. The image display system as claimed in claim 1, wherein the alkali metal or alkaline earth metal compound is a fluoride containing Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr, or Ba. 3. The image display system as claimed in claim 2, wherein the alkali metal or alkaline earth metal compound is NaF, KF, RbF, CsF, BeF ₂ , MgF ₂ , CaF ₂ , SrF ₂ , or BaF ₂ . 4. The image display system as claimed in claim 1, wherein the alkali metal or alkaline earth metal compound is a carbonyl compound containing Na, K, Rb, Cs, Be, Mg, Ca, Sr, or Ba. 5. The image display system as claimed in claim 4, wherein the alkali metal or alkaline earth metal compound is Li ₂ CO ₃ , LiCO ₃ , Na ₂ CO ₃ , NaCO ₃ , K ₂ CO ₃ , KCO ₃ , Rb ₂ CO ₃ , RbCO ₃ , Cs ₂ CO ₃ , CsCO 3 , BeCO, BeCO ₃ , MgCO, MgCO ₃ , CaO, Ca ₂ CO ₃ , _{CaCO 3} , SrCO, SrCO ₃ , BaCO or BaCO ₃ . 6. The image display system as claimed in claim 1, wherein the metal oxide layer comprises vanadium (V) metal oxide. 7. The image display system as claimed in claim 6, wherein the metal oxide layer comprises VO, V ₂ O ₃ , VO ₂ , or V ₂ O ₅ . 8. The image display system as claimed in claim 1, wherein the metal oxide layer comprises WO, W ₂ O ₃ , WO ₂ , WO ₃ , or W ₂ O ₅ . 9. The image display system as claimed in claim 1, wherein the semiconductor compound layer comprises Si, Ge, GaAs, SiC, or SiGe. 10. The image display system as claimed in claim 1, wherein the film layer with alkali metal or alkaline earth metal compound is doped with electron transport material. 11. The image display system as claimed in claim 1, wherein the composite electrode structure further comprises a metal layer disposed between the film layer having alkali metal or alkaline earth metal compound and the metal oxide layer or semiconductor compound layer. 12. The image display system as claimed in claim 8 or 11, wherein the metal layer comprises Al, Ag, Au, or alloys thereof. 13. The image display system of claim 1, further comprising a display panel, wherein the electroluminescent diode is a part of the display panel. 14. The image display system as claimed in claim 13, further comprising an electronic device, the electronic device comprising: the display panel; and The input unit is connected with the display panel. 15. The image display system as claimed in claim 14, wherein the electronic device is a mobile phone, a digital camera, a personal data assistant, a notebook computer, a desktop computer, a television, a car monitor, or a portable DVD player .

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