KR20160044643A - Light Emitting Device - Google Patents

Abstract

The organic light emitting device according to the present invention may include a first light emitting device and a second light emitting device on the first light emitting device. The first light emitting device may include a first substrate, a first transparent electrode, a first light emitting layer, a second transparent electrode, and a capping layer sequentially stacked. The second light emitting device may include a second substrate, a third transparent electrode, a second light emitting layer, and a reflective electrode. The first light emitting device may further include a first light extracting layer formed on the first substrate or the first transparent electrode. The second light emitting device may further include a second light extracting layer formed on the second substrate or the third transparent electrode.

Description

[0001] Light Emitting Device [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting device, and more particularly to a color variable light emitting device.

In a light emitting device, for example, an organic light emitting diode, a hole supplied from an anode electrode and an electron supplied from a cathode electrode form an exciton in an organic light emitting layer, It is a device that emits light in the process. Organic light emitting diodes have been developed and applied to display devices due to their wide viewing angle, fast response speed and high color recall ratio. A stacked light emitting device has been proposed for obtaining a device with high brightness and long life, but the efficiency is reduced in white light and the spectrum varies depending on the viewing angle.

It is an object of the present invention to provide a color variable light emitting device which stabilizes color change characteristics according to a viewing angle and has improved light extraction efficiency.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not intended to limit the invention to the precise forms disclosed. Other objects, which will be apparent to those skilled in the art, It will be possible.

The present invention relates to a light emitting device. The light emitting device of the present invention includes a first substrate, a first transparent electrode, a first light emitting layer including a first transparent electrode, a first light emitting layer emitting a first wavelength light, a second transparent electrode, and a capping layer, A second light emitting element disposed on the capping layer and including a second substrate, a third transparent electrode, a second light emitting layer emitting light of a second wavelength, and a reflective electrode stacked in sequence, And a second light extracting layer laminated between the second substrate and the second light emitting layer. The first light extracting layer may include a first light extracting layer and a second light extracting layer, And the second light extracting layer may transmit the light of the second wavelength.

According to an embodiment, the light of the first wavelength may be in a complementary relation with the light of the second wavelength.

According to one embodiment, the first light extracting layer may include a random scattering layer.

According to one embodiment, the second light extracting layer may include any one selected from a photonic crystal, a microcavity, and a scattering layer.

According to one embodiment, the first light extracting layer may be formed on the first substrate, and the second light extracting layer may be formed on the second substrate.

According to an embodiment, the first transparent electrode and the third transparent electrode may be an anode, and the second transparent electrode and the reflective electrode may be a cathode.

According to an embodiment, the first light emitting layer and the second light emitting layer may be organic light emitting layers.

According to one embodiment, the first wavelength may be a red wavelength and the second wavelength may be a blue wavelength.

According to one embodiment, the second transparent electrode may include Al and Ag.

According to one embodiment, the capping layer may reflect light of the first wavelength and transmit light of the second wavelength.

The organic light emitting device according to the present invention includes a first light extracting layer for transmitting light of a first wavelength and a light of a second wavelength and a second light extracting layer for transmitting light of a second wavelength, Characteristics stabilization and high light extraction efficiency can be provided.

A first light emitting element and a second light emitting element to provide reliable color variable performance.

1 is a schematic view of a general organic light emitting device.
2 is a schematic view showing an organic light emitting device according to the present invention.
3 is a schematic view of a first light emitting layer of an organic light emitting device according to the present invention.
4 is a schematic view of a second light emitting layer of an organic light emitting device according to the present invention.
5 is a graph of spectral characteristics at various color temperatures of an organic light emitting device according to the present invention.
FIG. 6 is a color coordinate diagram at various color temperatures of the organic light emitting device according to the present invention.
7 (a) is a graph of spectral characteristics according to viewing angles of a general organic light emitting device.
7 (b) is a graph of spectral characteristics according to viewing angles of an organic light emitting diode according to the present invention.
8 is a graph of light distribution according to the viewing angle of the organic light emitting diode according to the present invention.

In order to fully understand the structure and effects of the present invention, preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below. The present invention may be embodied in various forms, and various modifications may be made. It will be apparent to those skilled in the art that the present invention may be embodied in many other specific forms without departing from the spirit or essential characteristics thereof. Those of ordinary skill in the art will understand that the concepts of the present invention may be practiced in any suitable environment.

The terminology used herein is for the purpose of illustrating embodiments and is not intended to be limiting of the present invention. In the present specification, the singular form includes plural forms unless otherwise specified in the specification. It is to be understood that the phrase "comprises" and / or "comprising" is used herein to mean excluding the presence or addition of one or more other components, steps, operations, and / I never do that.

When a layer is referred to herein as being on another layer or substrate, it may be formed directly on another layer or substrate, or a third layer may be interposed therebetween.

The terms used in the embodiments of the present invention may be construed in a sense generally known to those skilled in the art unless otherwise defined.

1 shows a general organic light emitting device. A general organic light emitting device may include a first electrode 120, an organic light emitting layer 130, and a second electrode 140 sequentially provided on a substrate 110.

The substrate 110 provides the mechanical strength of the organic light emitting device and serves as a transparent window. The substrate 110 may comprise glass or plastic that is light transmissive. For plastic, polyethylene terephthalate (PET), polycarbonate (PC), polyethersulfone (PES), or polyimide (PI) may be used.

The first electrode 120 and the second electrode 140 may each be an anode or a cathode. The first electrode 120 and the second electrode 140 may be transparent electrodes, for example, ITO (Indium Tin Oxide). The second electrode 140 has a polarity opposite to that of the first electrode 120.

Referring to FIG. 1, an organic light emitting layer 130 is provided between the first electrode 120 and the second electrode 140. The organic light emitting layer 130 may include an organic material. The organic light emitting layer 130 emits light of a specific wavelength while emitting energy generated upon recombination of electrons and holes.

2 is a schematic view showing the structure of an organic light emitting device according to the present invention. Referring to FIG. 2, the organic light emitting device according to the present invention may include a first light emitting device 200 and a second light emitting device 300 on the first light emitting device 200. The first light emitting device 200 may include a first substrate 210, a first transparent electrode 230, a first light emitting layer 240, a second transparent electrode 250, and a capping layer 260 that are sequentially stacked. have. The second light emitting device 300 may include a second substrate 310, a third transparent electrode 330, a second light emitting layer 340, and a reflective electrode 350. The first light emitting device 200 may further include a first light extracting layer 220 formed on the first substrate 210 or the first transparent electrode 230. The second light emitting device 300 may further include a second light extracting layer 320 formed on the second substrate 310 or the third transparent electrode 330.

The first substrate 210 may be a glass substrate.

The first light extracting layer 220 may have a random scattering layer. The random nanostructures may include irregular structures of several hundred nanometers in size. The irregular structures may be irregularly arranged without having a constant period. The random nanostructure generates a diffraction effect and acts as a light scattering layer.

The first transparent electrode 230 and the second transparent electrode 250 may each be an anode or a cathode. The first transparent electrode 230 may include, for example, indium tin oxide (ITO). The second transparent electrode 250 may have an opposite polarity to the first transparent electrode 230. The second transparent electrode 250 may comprise, for example, Al and / or Ag.

The first light emitting layer 240 is formed between the first transparent electrode 230 and the second transparent electrode 250. The first light emitting layer 240 may include an organic material. Referring to FIG. 3, the first light emitting layer 240 may include a hole transport layer 241, a spin layer 242, an electron transport layer 243, and an electron injection layer 244 stacked in that order.

The capping layer 260 may comprise NPB (4,4'-bis (N- (1-naphthyl) -N-phenylamino) biphenyl. The capping layer 260 reflects the light 410 of the first wavelength generated in the first light emitting layer 240 and transmits the light 420 of the second wavelength emitted from the second light emitting layer 340.

The second substrate 310 may be a glass substrate.

The second light extracting layer 320 may have a photonic crystal, a microcavity, or a scattering layer. Photonic crystals are arranged in a nanometer scale with a constant periodicity and can transmit or reflect only light of a specific wavelength. The photonic crystal can not transmit light in a planar direction along a planar optical waveguide formed in the organic light emitting device so that light can be diverted to the outside without forming a waveguide mode. The micro cavity is a structure that improves the emission speed of light by using the microscopic vibration effect. The micro cavities generate resonance by forming a bragg mirror or a metal mirror layer on both sides with a spacer layer interposed therebetween. Since light of a specific wavelength band is strongly emitted, the micro cavity can be advantageously applied to monochromatic light. The scattering layer is a structure for extracting light using scattering effect. Application of light scattering layer increases light extraction efficiency, less color change with viewing angle, and brightness of panel is uniform.

The third transparent electrode 330 and the reflective electrode 350 may be an anode or a cathode. The third transparent electrode 330 may have, for example, indium tin oxide (ITO). The reflective electrode 350 may have a polarity opposite to that of the third transparent electrode 330. The reflective electrode 350 is a reflective layer that reflects all the light in the direction of the reflective electrode. The reflective electrode 350 may be a thick metal capable of total reflection, and may include, for example, Ag, Al, Mg, Mo, or an alloy thereof.

The second light emitting layer 340 is formed between the third transparent electrode 330 and the reflective electrode 350. The second light emitting layer 340 may include an organic material. 4, the second light emitting layer 340 includes a hole injecting layer 341, a hole transporting layer 342, a spinning layer 343, an electron transporting layer 344, and an electron injecting layer 345 stacked in this order. .

The light 410 of the first wavelength emitted from the first light emitting layer 240 may be complementary to the light 420 of the second wavelength emitted from the second light emitting layer 340.

<Experimental Example>

A method of forming an organic light emitting device according to an embodiment of the present invention will be described by way of example. Referring to Figs. 2 to 4, a first substrate 210 is prepared. The first substrate 210 may be a glass substrate. A random scattering layer is deposited on the first substrate 210 to a thickness of 200 nm to 500 nm to form a first light extracting layer 220. ITO (Indium Tin Oxide) is deposited to 100 nm on the first light extracting layer 220 to form a first transparent electrode 230.

Referring to FIG. 3, an HTL (Hole Transport Layer) 241, an EML (Emissive Layer) 242, an ETL (Electron Transport Layer) ) 243 and an EIL (electron injection layer, electron injection layer) 244 are stacked to form a first light emitting layer 240. Specifically, 10 nm of LG101 (a hole transport layer material produced by LG Chem), 10 nm of TAPC (1-Bis [4- [N, N-di (4-tolyl) amino] phenyl ] -cyclohexane 45 nm, LG101 5 nm, TAPC 45 nm, LG101 5 nm and TAPC 50 nm are laminated to form HTL 241. Bis (2-methyldibenzo [f, h] quinoxaline) (acetylacetonate (2-ethylhexyl) ) iridium (III)) is deposited to a thickness of 10 nm to form a RED EML (242) emitting red light. An ETL 243 of 55 nm is formed on the RED EML 242. ETL 243 is BmPyPB (1,3-bis (3,5-dipyrid-3-yl-phenyl) benzene). 1 nm of LiF is laminated on the ETL 243 to form the EIL 244.

Referring again to FIG. 2, a second transparent electrode 250 is formed by laminating Al 1.5 nm and Ag 20 nm on the first light emitting layer 240. NPB (4,4'-bis (N- (1-naphthyl) -N-phenylamino) biphenyl is deposited to a thickness of 10 nm to 140 nm on the second transparent electrode 250 to form a capping layer 260.

Referring again to FIG. 2, a second substrate 310 is formed on the capping layer 260. The second substrate 310 may be a glass substrate. A second cavity 320 is formed by laminating a micro cavity of 200 nm to 500 nm on the second substrate 310. ITO (Indium Tin Oxide) is deposited to a thickness of 100 nm on the second light extracting layer 320 to form a third transparent electrode 330.

Referring to FIG. 4, a HIL (Hole Injection Layer) 341, an HTL 342, an EML 343, an ETL 344, and an ETL 344 are formed on the third transparent electrode 330, And an EIL 345 are stacked to form a second light emitting layer 340. [ Specifically, 110 nm / 10 nm of NPB / TCTA (tetra (4-carbazoyl-9-ylphenyl) amine) is sequentially deposited on the third transparent electrode 330 to form HIL 341 / HTL 342 . 20 nm of SH03: SD1 is deposited on the HTL 342 to form a BLUE EML 343 that emits blue light. 30 nm / 1 nm of BmPyPB / LiF is sequentially laminated on the BLUE EML 343 to form an ETL 344 / EIL 345.

Referring again to FIG. 2, a reflective electrode 350 is formed by stacking 100 nm of Al on the second light emitting layer 340.

The adjustment of the color temperature and the color coordinate value of the organic light emitting diode according to one embodiment of the present invention will be described by way of example.

FIG. 5 shows spectral characteristics at various color temperatures of an organic light emitting device according to the present invention. FIG. 6 shows the color coordinates in various color temperatures of the organic light emitting device according to the present invention.

Referring to FIGS. 5 and 6, it can be seen that the color temperature and color coordinates of the present invention can be changed by adjusting the current density ratio of the first light emitting device and the second light emitting device.

5, J _TOLED is the current density of the first light emitting device. J _BOLED is a current density applied to the second light emitting element. J _TOLED : When J _BOLED = 10: 0, the color temperature corresponds to ORANGE / RED. The color temperature rises as J _BOLED becomes larger than J _TOLED . J _TOLED : If J _BOLED = 0: 10, the graph has a color temperature corresponding to BLUE.

Each point in FIG. 6 is a color coordinate value corresponding to the color temperature of FIG. The results are as follows.

Color temperature (K) CIEx CIEy Blue 0.18 0.20 106367 0.30 0.27 5729 0.34 0.29 3472 0.39 0.32 2447 0.45 0.35 Orange / Red 0.57 0.42

Therefore, the color temperature and the color coordinate value can be adjusted by the current density.

The color change problem and the light extraction efficiency improvement according to the viewing angle of the organic light emitting diode according to an embodiment of the present invention will be described by way of example.

7A is a graph of light intensity according to a viewing angle of 0 ° to -70 ° of a general organic light emitting device. The EL intensity (intensity of light) has different values depending on the viewing angle. FIG. 7 (b) is a graph when a random scattering layer according to an embodiment of the present invention is applied. There is little change in EL intensity with viewing angle. Therefore, the problem of color change according to the viewing angle is improved by applying the random nano structure to the organic light emitting device according to the present invention.

FIG. 8 is a graph of a white light distribution result of (b) when a general case (a) and a random scattering layer are applied. When the random nano structure is applied, the light distribution result of (b) is higher than that of (a). Therefore, it can be seen from FIG. 8 that the random nanostructure is disposed in the present invention to improve power efficiency and external quantum efficiency by improving the light distribution at all angles.

It will be understood by those skilled in the art that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. It is therefore to be understood that the above-described embodiments and experiments are illustrative in all aspects and not restrictive. The scope of the present invention is defined by the appended claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be interpreted as being included in the scope of the present invention.

110, 210, and 310, a substrate 120, a first electrode
130 ... light emitting layer 140 ... second electrode
200: first light emitting device 220, 320: light extracting layer
230, 250, and 330, transparent electrodes 240 and 340,
241, 342 ... Hole transport layer 242, 343 ... Radiation layer
243, 344 electron transport layer 244, 245 electron injection layer
260 ... capping layer 300 ... second light emitting element
341 ... hole injection layer 350 ... reflective electrode
410 ... light of the first wavelength 420 ... light of the second wavelength

Claims (1)

A first light emitting device including a first substrate, a first transparent electrode, a first light emitting layer emitting light of a first wavelength, a second transparent electrode, and a capping layer stacked in order;
A second light emitting device disposed on the capping layer and including a second substrate, a third transparent electrode, a second light emitting layer emitting light of a second wavelength, and a reflective electrode sequentially stacked; And
And a second light extracting layer including a first light extracting layer laminated between the first substrate and the first light emitting layer, the second light extracting layer being laminated between the second substrate and the second light emitting layer,
Wherein the first light extracting layer transmits the light of the first wavelength and the light of the second wavelength, and the second light extracting layer transmits the light of the second wavelength.

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