TWI284010B - Organic electroluminescence device and organic electroluminescence panel - Google Patents

Abstract

The present invention aims to provide an organic electro-luminescence (OEL) device, which will not deteriorate along with the brightness but can increase the external quantum efficiency and improve the contrast, and an OEL panel using the OEL device. Mainly, a transparent conductive film, formed by any one of In2O3-ZnO, In2O3-SnO2, ZnO, and SnO2, is installed on the surface of the OEL layer of metal electrode in the OEL device. The thickness of the transparent conductive film is set to satisfy the equation: L=(2n+1)*lambda/4, where n=0, 1, 2, ..., L is the optical distance from the OEL layer to the metal electrode, and lambda is the light wavelength. Since the light reflected by the metal electrode can generate interference and enhance bonding in the device, the OEL device will not deteriorate along with the brightness but can increase the external quantum efficiency and improve the contrast.

Description

1284010 (1) 玖 发明 发明 发明 发明 发明 发明 发明 发明 发明 发明 有机 有机 有机 有机 有机 有机 有机 有机 有机 有机 有机 有机 有机 有机 有机 有机 有机 有机 有机 有机 有机 有机 有机 有机 有机 有机 有机 有机 有机 有机 有机 有机 有机 有机 有机 有机 有机An organic electroluminescent device that improves contrast and an organic electroluminescent panel using the element.

[Prior Art] In 1987, after Tang published a device with a two-layer laminate structure and a high-efficiency organic electroluminescence device (CW Tang et al., Appl. Phys· Lett. 51, 9 1 3 (1 9 8 7)), a variety of organic electroluminescent devices have been developed, and some of them have been put into practical use.

4 is a view for explaining the configuration of a conventional organic electroluminescent device, in which a positive hole transfer layer 42, a positive hole injection layer 43, a light emitting layer 44, an electron transport layer 45, and the like are sequentially laminated on the transparent electrode 41 of the anode. The electron injection layer 46 is provided with a metal electrode 47 belonging to the cathode on the electron injection layer 46, and the quantum efficiency of the organic electromagnetism of the structure shown in Fig. 4 is considered as follows. First, the positive holes and electrons reached by the anode and the cathode form an electron-positive hole pair in the light-emitting layer, and become an illuminating exciter'. However, the probability of generating the luminescent excitons is about 25 %. On the one hand, the efficiency n of the light generated in the light-emitting layer from the outside of the element is obtained by the refractive index of the light-emitting layer as follows. -4- (2)1284010 [Number 3]

(1) The refractive index of the general light-emitting layer is 1.6, and the external extraction efficiency is about 20%. Thus, the theoretical limit of external quantum efficiency is obtained by the product of the probability of generation of luminescent excitons (about 25 %) and external extraction efficiency (about 20%), which is about 5%. [Problem to be Solved by the Invention] However, the external quantum efficiency of an actual organic electroluminescence device is less than about 3% of the theoretical 値 about 6 times. Therefore, in order to take out light of a certain brightness to the outside, If the current flowing into the element is too large, and the brightness continues to deteriorate, the problem of an increase in power consumption occurs. However, the actual panel is difficult to see the contrast problem of the display by external light, which causes practical problems. One reason for the contrast reduction is that the metal electrode reflects external light. The present invention has been made in view of the above problems, and an object of the invention is to provide an organic electroluminescent device which can improve the contrast and which can improve the external quantum efficiency without deteriorating the brightness, and an organic electroluminescent panel using the same. . [Means for Solving the Problem] In order to solve the problem, the invention of the invention claims (3) 1284010 of the invention belongs to an organic electroluminescence light including an organic light-emitting layer between a metal electrode and a transparent electrode. The organic electroluminescence device of the portion is characterized in that a transparent conductive film is provided on a surface of the metal electrode on the side of the organic electroluminescence portion, and the film thickness of the transparent conductive film is L from the organic light-emitting layer to the metal The optical distance of the electrode and λ are the emission wavelengths of the organic light-emitting layer, and are set so as to satisfy the following formula. [Equation 4] L = -λ (η = 051? 2, ...) 4 The invention described in claim 2 belongs to the invention in which the organic light-emitting layer is provided between the metal electrode and the transparent electrode. An organic electroluminescence device of an electromechanical excitation portion, characterized in that a transparent conductive film is provided on a surface of the metal electrode on the side of the organic electroluminescence portion so as to have a wavelength different from an emission wavelength of the organic electroluminescence layer Light is absorbed by the metal electrode or/and the transparent conductive film, and only light of a wavelength emitted from the organic electroluminescence layer is emitted from the transparent electrode. The invention described in claim 3 is an organic electroluminescence device including an organic electroluminescence portion including an organic light-emitting layer between a metal electrode and a transparent electrode, and is characterized in that the metal electrode is A transparent conductive film is provided on a surface on the side of the organic electroluminescence portion, wherein the film thickness of the transparent conductive film is L, the optical distance from the organic light-emitting layer to the metal electrode, and λ is the emission wavelength of the organic light-emitting layer. And set the following formula, -6- (4) 1284010 [number 5] L = 2n + l 4 (π = 0,1,2"·.)

Light having a wavelength different from an emission wavelength of the organic electroluminescence layer is absorbed by the metal electrode or/and the transparent conductive film, and only light having a wavelength emitted from the organic electroluminescence layer is received from the transparent electrode Shoot out. The invention described in claim 4 is the organic electroluminescent device according to any one of claims 1 to 3, wherein the material of the transparent conductive film is Ιη203 — ZnO, In2〇 3—Sn02, ZnO, and Sn02 are all characterized.

The invention described in claim 5 is the organic electroluminescent device according to the second or third aspect of the invention, wherein the transparent conductive film is coated with impurities and coated with the organic electroluminescent light. The layer emits the same color of light. The invention of claim 6 is the organic electroluminescent device according to claim 5, wherein the organic electroluminescent layer emits blue light, and the transparent conductive film is used at less than 1%. The concentration is composed of any one of In2〇3-ZnO, In2〇3-Sn02, ZnO, and SnO 2 containing any impurity of CuO, Co, or Ti, and the transparent conductive film is characterized by absorbing blue light. The invention described in claim 7 is the organic electroluminescent device described in any one of claims 2, 3, and 6 - (5) 1284010' The layer emits blue light, and the metal electrode is formed of Zn, Mo, Cr or an alloy of the metals, which is characterized by absorbing blue light. The invention described in claim 8 is a black-and-white panel or a partial color panel, and is characterized by comprising the organic electroluminescent device according to any one of claims 1 to 5.

The invention described in claim 9 is a color conversion type color panel, which is characterized in that: the organic electroluminescence element described in claim 6 of the patent application scope, and a blue monochrome backlight, and In the color conversion filter, the transparent conductive film of the organic electroluminescence element absorbs light other than blue, and only the blue monochromatic light from the backlight is reflected by the metal electrode.

Furthermore, the invention described in claim 10 is a color conversion type color panel, and is characterized in that the organic electroluminescence element described in claim 7 and blue monochrome are provided. The backlight and the color conversion filter absorb light other than blue at the metal electrode and reflect only blue monochromatic light from the backlight. [Embodiment] [Embodiment of the Invention] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Fig. 1 is a view showing an example of the configuration of an organic electroluminescence device of the present invention formed on a substrate, wherein the organic electroluminescence device includes an organic electroluminescence portion composed of a plurality of organic layers including an organic light-emitting layer. 'Specific-8-(6) 1284010 is a layer of a positive hole transfer layer 12, a positive hole injection layer 13 and a light-emitting layer 14; and an electron transport layer. The electron injection layer 16 is provided with a transparent conductive film 17 on the electron injection layer 16, and a metal electrode 18 belonging to the metal layer of the cathode is provided on the transparent conductive film 17. Further, in contrast to the organic electroluminescent element of the present invention, the glass substrate may be provided on either the transparent electrode 11 of the anode or the metal electrode 18 of the metal layer of the cathode. Among the light emitted from the light-emitting layer 14, the light radiated to the side of the positive hole injection layer 13 passes through the positive hole injection layer 13 and the positive hole transfer layer 12, and is taken out to the outside by the transparent electrode 1 1 . At the same time, light radiated to the side of the electron transport layer 15 passes through the electron transport layer 15, the electron injection layer 16, and the transparent conductive film 17, and is reflected at the metal electrode 18 to return to the inside of the element. Therefore, the reflected light is not attenuated inside the element, and can be taken out to the outside to improve the external quantum efficiency. That is, the layers of the electron transport layer 15 , the electron injection layer 16 , and the transparent conductive film 17 constituting the element are di (i = 1, 2, 3) and have a refractive index of ~ (i = 1, 2, 3). The optical distance L from the light-emitting layer 14 to the metal electrode 18 is obtained by the following equation of the sum of the optical distances of the layers. [Equation 6] L = [ Ά (2) When the light is reflected at the interface between the metal electrode 18 and the transparent conductive film 17, the phase of the light is reversed, so the light will enhance the bonding condition inside the element, and the light -9 - (7) 1284010 The wavelength is λ ' [7] L = % "t?. χ (/7 = 〇,1,2,...) (3) 4 The metal electrode 18 is used as the cathode 'in the light-emitting layer The electron transport layer 15, the electron injection layer 16, and the transparent conductive film 17' are interposed between the layers 14 so that the external quantum efficiency can be improved as long as the optical distance is designed to satisfy the formula (3). However, when the thickness of the electron injecting layer 16 is required to be as thin as about 5 to 1 nm, and the thickness of the electron transporting layer 15 is too thick, the organic electroluminescent element of the present invention may have a problem that the brightness of the element is significantly deteriorated. Then, a transparent conductive film 17 is disposed between the electron injection layer 16 and the metal electrode 18, and the light reflected by the metal electrode 18 is set to satisfy the above-mentioned interference condition, and the film thickness of the transparent conductive film 17 is set. The intensity does not decay and the light is taken out to the outside to increase the external quantum efficiency. The method of adjusting the film thickness of the transparent conductive film 17 to set the optical distance so that the external quantum efficiency is maximized is a black-and-white panel or a partial color panel that originally emits light using a single-color backlight, and light emitted from a monochrome backlight. A color panel that receives light in a color conversion layer and converts it into a color conversion method of RGB illumination is particularly useful. One of the practical problems of the organic electroluminescence panel is that the contrast is reduced by external light. This reason is clearly determined that the external light is directly reflected by the metal layer. According to the formula (3), only the wavelength light of the wavelength -10 (8) 1284010 with strong interference is limited, and only the relationship of the light of a specific wavelength is reflected, and the intensity of the light of the wavelength of the light of the formula (3) is not reduced, and the light intensity is known. The organic electroluminescent device of the invention is also used to enhance the contrast of the organic electroluminescent panel. Further, in order to improve the contrast, the transparent electrode and the metal layer are laminated to form a reverse layer, and the transparent electrode layer in the reflective layer is coated with a luminescent color to form a structure that does not reflect outside the light, or the metal layer material has an absorbing color. The material of the external characteristics is very effective. Therefore, it is a method of taking out the wavelength light which is not considered to be absorbed outside the transparent electrode, and is absorbed by the laminated portion of the transparent electrode and the metal layer and absorbed by the metal layer material. Further, in this case, the optical distance of the layer interposed between the metal electrode and the light-emitting layer is desirably configured to satisfy the formula (3), but the present invention is not limited thereto. In particular, the color conversion method is a blue backlight. It is effective to use a metal with a large blue reflection coefficient compared to red. Specifically, Zn, Mo, and Cr can be used. Further, the bluening method of the transparent electrode can be achieved by adding only 50% or less of CuO Co, Ti or the like to the oxide layer constituting the transparent electrode. The configuration of the organic electroluminescence device of the present invention may be the configuration shown in Fig. 2, in addition to the configuration shown in Fig. 1. Fig. 2 is a view showing a configuration in which the lower electrode of the organic electroluminescence element is used as a pole, and the metal electrode 28, the anode transparent conductive film 27, the positive hole injection layer 23, and the positive hole transmission layer are sequentially laminated on the substrate 29. 22. The composition of the hair layer 24, the electron transport layer 25, the electron injection layer 26, and the transparent electrode of the cathode. In this example, the electron injection layer 26 and the transparent electrode 21 portion of the cathode are formed by an alkali, an alkaline earth metal oxide, a fluoride, a boride, and a helper color. The electrode film of the chlorinated 11 - (9) 1284010 compound forms an electron injecting layer 26, and a thin film of a metal such as A1 is deposited on the layer, and a structure of Ιη203-ZnO oxide layer (IZO) is further provided on the layer, or It is considered that the transparent electrode 2 1 made of a transparent oxide such as IZO is directly deposited on the electron injection layer 26. Further, in addition to the organic electroluminescent device of the layer structure shown in Figs. 1 and 2, the present invention can be applied, for example, to a conventional organic electroluminescent device which does not have a positive hole transmission layer structure or the like. All organic electroluminescent elements are constructed. [Embodiment 1] Fig. 3 is a cross-sectional view showing a color conversion color panel using the organic electroluminescence device of the present invention. A metal electrode 303 with Cr (5 nm) / Pt (100 nm) as a reflective metal is deposited on the substrate 301 having the TFT 312, and a ZnO ZnO oxide layer (IZO: refractive index 2.2 nm) is deposited thereon as an anode. The transparent conductive film 306, the metal electrode 303 of the reflective metal used here may be a metal or an alloy of a conductor having a thickness of 4 nm or less, and is not limited to a laminated body of Cr/Pt. The film formation of IZO is by sputtering, but it may be another film forming method such as electron beam evaporation method or resistance heating vapor deposition method. On the transparent conductive film 404, a positive hole injection layer 305, a positive hole transfer layer 306, and a light-emitting layer 307 are sequentially stacked by a resistance heating vapor deposition method, and the A1 coordination of the 8-hydroxyquinoline is further carried out. A 20 nm layer of the (Alq3) layer is used as the electron transport layer 308. The layered portion 3 09 of the electron injecting layer and the upper transparent electrode is formed by depositing LiF stacking -12-(10) 1284010 〇.5 nm as an electron injecting layer, and stacking 1A1 and 220 nm of JZO on the upper transparent electrode, and finally stacking SiON 3 00nm is composed of a protective film. The optical distance of the organic electroluminescence element of this configuration is the transparent conductive film 304 of the IZO constituting the lower electrode belonging to the anode, the positive hole injection layer 305, the positive hole transmission layer 306, and the metal electrode 30,000. Make adjustments between Pt membranes. Because the original wavelength of the backlight of the color conversion method is 470 nm, 'the positive hole injection layer 3 0 5 is stacked 80 nm, the positive hole transmission layer 3 06 is 20 nm, so the organic matter has a refractive index of 1.85, and the interference condition of the formula (3), IZO The film thickness was 1 83 nm. Further, 0.6% of CuO was added to the IZO film of the transparent conductive film 304 constituting the lower electrode, and blue was applied. Thus, a protective layer 316 is formed on the substrate 301 formed of the element, and the substrate 310 on which the RGB color conversion filters 311, 312, and 313 are previously formed face each other, and the gel is filled in the gap 3 1 4 In the state of the outer peripheral portion of the element, the sealant 3 15 is sealed to complete the panel. Here, the color conversion filter refers to a filter provided with a color filter or/and a fluorescent filter. As a result of comparing the panel characteristics of the conventional embodiment with the panel characteristics of the conventional configuration, the external extraction efficiency can be increased from 2 · 〇 % to 3 · 〇 %, and the current flowing in the same brightness can be reduced by 2/3. The same result was obtained when the contrast experiment was performed at a black panel or partial color with a contrast ratio of 1 000 Lx and 100 cd/m2 and 200:1 °. [Example 2] -13- (11) 1284010 Substituting Ιη2 03 - ZnO The same thickness as in Example 1 was carried out using ln2 03 -Sn02 (ITO) (refractive index 2.0) having a film thickness of 201 nm as a transparent conductive film material. In the comparison, the same effects as in the first embodiment can be obtained. The ITO film can be formed by a sputtering method, a vapor deposition method, a CVD method or the like. The transparent conductive film material is Ζ η Ο or S η Ο 2, and the same result can be obtained when the optical distance is matched. [Effect of the Invention] As described above, according to the present invention, a transparent conductive film is provided on the surface of the metal electrode of the organic electroluminescent device on the side of the light-emitting layer, and the film thickness of the transparent conductive film is adjusted, and the light is reflected by the metal electrode. Interference in the component and enhanced bonding will not improve the external quantum efficiency as the brightness deteriorates. It is because the metal electrode and the transparent conductive film absorb light of a specific wavelength, so that the contrast can be improved, thereby providing no As the luminance is deteriorated, the external quantum efficiency can be improved, and the organic electroluminescence element and the organic electroluminescence panel using the element can be improved. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a view showing an example of the configuration of an organic electroluminescence device of the present invention. Fig. 2 is a view for explaining a second configuration example of the organic electroluminescence device of the present invention. Fig. 3 is a cross-sectional view showing a color panel of a color conversion method using the organic electroluminescence element of the present invention. -14- (12) 1284010 Fig. 4 is a view showing the configuration of a conventional organic electroluminescent device. [Description of Symbols] 1 2 2, 4 1 Transparent Electrodes 12, 11, 42, 306 Positive Hole Transfer Layers 13, 24, 43, 305 Positive Hole Injection Layers 14, 24, 44, 307 Light Emitting Layers 15, 25' 45, 308 electron transport layer 16, 26, 46 electron injection layer 17, 27, 304 transparent conductive film 18, 28, 47, 303 metal electrode 29 ^ 30 1 '310 substrate 302 TFT 309 laminate portion 3 11 , 3 1 2 3 1 3 Color Conversion Filter 3 14 Gel 315 Peripheral Sealant

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Claims (1)

1284010 ί. - 8 ./ ',.- - , ·' ·.·:; ,. -7 Pick up, apply for patent coverage 92 1 1 573 6 Patent application Chinese application patent scope amendments January 1996 8th Correction 1 · An organic electroluminescence device is an organic electroluminescence device having an organic electroluminescence portion including an organic light-emitting layer between a metal electrode and a transparent electrode, and is characterized in that: a transparent conductive film is provided on a surface of the metal electrode on the side of the organic electroluminescence portion, and the film thickness of the transparent conductive film is such that L is an optical distance from the organic light-emitting layer to the metal electrode, and λ is the organic light-emitting layer. The wavelength of the light is set in a manner that satisfies the following formula [number 1] L = 4 (π = 0 from ...) 2. An organic electroluminescence device comprising an organic electroluminescence device comprising an organic electroluminescence portion comprising an organic light-emitting layer between a metal electrode and a transparent electrode, wherein: the organic electro-excitation of the metal electrode a surface of the light portion side is provided with a transparent conductive film; light having a wavelength different from an emission wavelength of the organic electroluminescence layer is absorbed by the metal electrode or/and the transparent conductive film, and only the organic electroluminescence layer is Light of a wavelength of light is emitted from the aforementioned transparent electrode by 1284010. 3. An organic electroluminescence device, which is an organic electroluminescence device comprising an organic electroluminescence portion including an organic light-emitting layer between a metal electrode and a transparent electrode, wherein: the organic electrode of the metal electrode a transparent conductive film is provided on a surface on the side of the excitation light portion; the film thickness of the transparent conductive film is such that L is an optical distance from the organic light-emitting layer to the metal electrode, and λ is an emission wavelength of the organic light-emitting layer, and the film satisfies the following formula The way to set, Φ [number 2] 〇 7 = 051 again...) Light having a wavelength different from an emission wavelength of the organic electroluminescence layer is absorbed by the metal electrode or/and the transparent conductive film, and only light having a wavelength emitted from the organic electroluminescence layer is received from the transparent electrode Shoot out. The organic electroluminescent device according to any one of the items 1 to 3, wherein the transparent conductive film is made of ln203 - ΖηΟ, Iη2 〇3 - Sn〇2, ΖηΟ, Sn〇2 Any ~^ species. The organic electroluminescent device according to claim 2, wherein the transparent conductive film is filled with an impurity and has the same color as that of the light emitted from the organic electroluminescent layer. 6. The organic electroluminescent device according to claim 5, wherein the organic electroluminescence layer emits blue light, and the transparent conductive film contains CxiO at a concentration of 1% or less. Any of the materials of any of Co or Ti, I112O3 - ΖηΟ 'Ιη2〇3 - Sn〇2, ΖηΟ, 811〇2; the transparent conductive film absorbs blue light. 7. The organic electroluminescent device of claim 2, wherein the organic electroluminescent layer emits blue light; and the metal electrode is made of Zn, Mo, Cr or an alloy of the metals. Formed; the metal electrode absorbs blue light. A black-and-white panel or a partial color panel, which is characterized by comprising the organic electroluminescent device according to any one of claims 1 to 5. 9. A color conversion type color panel, comprising: an organic electroluminescence element according to item 6 of the patent application scope, a blue monochrome backlight, and a color conversion filter; The transparent conductive film of the excitation light element absorbs light other than blue; the metal electrode reflects only the blue monochromatic aperture 10 from the backlight, and the color conversion method color panel is characterized in that: The organic electroluminescence device according to claim 7 or the blue monochromatic backlight and the color conversion filter; the metal electrode absorbs light other than blue, and reflects only from the former -3- 1284010 Backlit blue monochromatic light.