KR100915617B1 - Organic EL element and organic EL panel - Google Patents

Abstract

The present _{invention, In 2 O 3 -ZnO, In} 2 O 3 -SnO 2, ZnO, SnO 2 in any installation with one transparent conductive film formed, and the transparent conductive film has a thickness in the light emitting layer side of the metal electrode of the organic EL device L is the optical distance from the organic light emitting layer to the metal electrode, λ is the light emission wavelength,

(n = 0, 1, 2, ...)

(n = 0, 1, 2, ...)

By setting so that the light reflected from the metal electrode is enhanced by interfering in the device, the external quantum efficiency can be improved without deterioration of brightness and the contrast can be improved. To provide.

Description

Organic EL element and organic EL panel {ORGANIC EL DEVICE AND ORGANIC EL PANEL}

The present invention relates to an organic EL (electroluminescent) device and an organic EL panel, and more particularly, to an organic EL device capable of improving external quantum efficiency without accompanying deterioration of luminance and capable of improving contrast, and using the same. It relates to an organic EL panel.

Since the introduction of high efficiency organic EL devices as two-layer stacked devices by Tang in 1987 (CW Tang et al., Appl. Phys. Lett. 51, 913 (1987)), various organic EL devices have been It is being developed, and some of it has already been put to practical use.

4 is a view for explaining the structure of the conventional organic EL device, the hole injection layer 42, the hole transport layer 43, the light emitting layer 44, and the electron transport layer 45 on the transparent electrode 41 as an anode ) And the electron injection layer 46 are sequentially stacked, and a metal electrode 47 serving as a cathode is provided on the electron injection layer 46 to form an element.

The quantum efficiency of the organic EL element of the structure shown in FIG. 4 is considered as follows. First, holes and electrons reached from the anode and the cathode form electron-hole pairs in the light emitting layer to become luminescent excitons, and the probability of generating the luminescent excitons is about 25%. On the other hand, the efficiency of extracting the light generated in the light emitting layer to the outside of the device is obtained by the following equation with n being the refractive index of the light emitting layer.

................................

......................

Since the refractive index of a general light emitting layer is 1.6, this external extraction efficiency is about 20%. Thus, the theoretical limit of external quantum efficiency is about 5%, given by the product of the emission probability of the luminescent excitons (about 25%) and the external extraction efficiency (about 20%).

However, the actual external quantum efficiency of the organic EL device is about 3%, which is about 60% of the above theoretical value. Therefore, when the current flowing to the device to extract light having a constant brightness is increased, the luminance deteriorates. Progresses, and furthermore, a problem arises that the power consumption is increased.

Moreover, the problem of contrast which makes it difficult to see a display by external light in a real panel becomes a problem practically. Such a decrease in contrast can be considered as one cause of the metal electrode reflecting external light.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object thereof is to provide an organic EL device capable of improving external quantum efficiency without accompanying deterioration in luminance and capable of improving contrast and an organic EL panel using the same.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and the invention according to claim 1 is an organic EL device having an organic EL light emitting unit including an organic light emitting layer between a metal electrode and a transparent electrode, wherein the metal A transparent conductive film is provided on the surface of the organic EL light emitting part of the electrode, and the film thickness of the transparent conductive film is represented by the following formula, wherein L is the optical distance from the organic light emitting layer to the metal electrode, and λ is the light emission wavelength of the organic light emitting layer. It is characterized in that it is set to satisfy.

(n = 0, 1, 2,...) ...................

(n = 0, 1, 2, ...) ...................

In addition, the invention according to claim 2 is an organic EL device having an organic EL light emitting part including an organic light emitting layer between a metal electrode and a transparent electrode, wherein the conductive surface is transparent to the organic EL light emitting part side of the metal electrode. A film is provided, and light of a wavelength different from the light emission wavelength of the organic EL light emitting layer is absorbed into at least one or both of the metal electrode and the transparent conductive film, so that only light having a wavelength emitted from the organic EL light emitting layer is emitted from the transparent electrode. It is characterized in that the injection from.

In addition, the invention according to claim 3 is an organic EL device having an organic EL light emitting part including an organic light emitting layer between a metal electrode and a transparent electrode, wherein the conductive surface is transparent to the organic EL light emitting part side of the metal electrode. A film is provided, and the film thickness of the transparent conductive film is set so that L is the optical distance from the organic light emitting layer to the metal electrode, and λ is the light emission wavelength of the organic light emitting layer to satisfy the following equation,

(n = 0, 1, 2,....) ...................

(n = 0, 1, 2, ...) ...................

Light of a wavelength different from that of the organic EL light emitting layer is absorbed by the metal electrode or / and the transparent conductive film so that only light having a wavelength emitted from the organic EL light emitting layer is emitted from the transparent electrode. .

In the invention according to claim 4, the organic EL device according to any one of claims 1 to 3, wherein the material of the transparent conductive film is In ₂ O ₃ -ZnO, In _{It is} characterized by any one of ₂ O ₃ -SnO ₂ , ZnO, SnO ₂ .

In addition, the invention according to claim 5 is the organic EL device according to claim 2 or 3, wherein the transparent conductive film is formed by adding impurities and the color of light emitted from the organic EL light emitting layer. It is characterized by being colored in the same color.

In addition, the invention according to claim 6 is the organic EL device according to claim 5, wherein the organic EL light emitting layer emits blue light, and the transparent conductive film is any one of CuO, Co or Ti. containing the impurity at a concentration of 1% or less, and is composed of in ₂ O ₃ -ZnO, any material of the _{in 2 O 3 -SnO 2, ZnO} , SnO 2, wherein the transparent conductive film that absorbs light other than blue It features.

The invention according to claim 7 is the organic EL device according to any one of claims 2, 3, and 6, wherein the organic EL light emitting layer emits blue light. The metal electrode is made of Zn, Mo, Cr or an alloy of these metals, and the metal electrode absorbs light other than blue.

The invention according to claim 8 includes the organic EL device according to any one of claims 1 to 5 as a monochromatic panel or an area color panel.

The invention according to claim 9 is a color conversion system color panel, comprising the organic EL device according to claim 6, a blue monochromatic backlight, and a color conversion filter. Light other than blue is absorbed into the transparent conductive film of?, And only the blue monochromatic light from the backlight is reflected by the metal electrode.

Furthermore, the invention according to claim 10 is a color conversion system color panel, comprising the organic EL device according to claim 7, a blue monochromatic backlight, and a color conversion filter. It is characterized by absorbing light other than blue to reflect only blue monochromatic light from the backlight.

BRIEF DESCRIPTION OF THE DRAWINGS The figure for demonstrating the structural example of the organic electroluminescent element of this invention.

2 is a view for explaining a second configuration example of the organic EL device of the present invention.

3 is a cross-sectional view of a color conversion type color panel constructed using the organic EL device of the present invention.

4 is a diagram for explaining the structure of a conventional organic EL device.

(Explanation of the sign)

11, 21, 41 transparent electrode

13, 22, 43, 306 hole transport layer

12, 23, 42, 305 hole injection layer

14, 24, 44, 307 light emitting layer

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, 301, 310 substrates

302 TFT

309 stack

311, 312, 313 color conversion filters

314 gel body

315 outer sealant

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described with reference to drawings.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure for demonstrating the structural example of the organic electroluminescent element of this invention formed on a board | substrate, The said organic electroluminescent element is equipped with the organic electroluminescent part comprised from the several organic layer containing an organic luminescent layer, Specifically, The hole injection layer 12, the hole transport layer 13, the light emitting layer 14, the electron transport layer 15, and the electron injection layer 16 are sequentially stacked on the transparent electrode 11, which is an anode, and electron injection is performed. The transparent conductive film 17 is provided on the layer 16, and the metal electrode 18, which is a metal layer of the cathode, is provided on the transparent conductive film 17. Further, in constructing the organic EL device of the present invention, the glass substrate may be provided anywhere on the transparent electrode 11 as the anode or on the metal electrode 18 as the metal layer of the cathode.

The light emitted from the light emitting layer 14 toward the hole transport layer 13 is extracted through the hole transport layer 13 and the hole injection layer 12 to the outside from the transparent electrode 11 and at the same time, the electron transport layer ( The light emitted to 15 is transmitted through the electron transport layer 15, the electron injection layer 16, and the transparent conductive film 17, reflected by the metal electrode 18, and returned to the inside of the device. Therefore, if the reflected light can be extracted to the outside without attenuating the inside of the device, the external quantum efficiency can be improved.

That is, the thickness of each layer of the electron transport layer 15, the electron injection layer 16 and the transparent conductive film 17 constituting the device is d _i (i = 1,2,3) and the refractive index is n _i (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, which is the sum of the optical distances of these layers.

.....................................

.........................

When the light is reflected at the interface between the metal electrode 18 and the transparent conductive film 17, the light phase is inverted. Therefore, the condition for the light to be enhanced inside the device is that the wavelength of the light is?                 

(n = 0, 1, 2, ...) ...................

(n = 0, 1, 2, ...) ...................

Becomes

The metal electrode 18 is used as a cathode, and since the electron transport layer 15, the electron injection layer 16, and the transparent conductive film 17 exist between the light emitting layer 14, the optical distances of these layers are in charge. By designing to satisfy Eq. (5), it is possible to improve the external quantum efficiency.

However, since the thickness of the electron injection layer 16 needs to be made thin about 0.5 to 1 nm, and furthermore, when the thickness of the electron transport layer 15 is made thick, there is a problem that the luminance of the device is significantly degraded. In the device, a transparent conductive film 17 is provided between the electron injection layer 16 and the metal electrode 18, and the light reflected from the metal electrode 18 satisfies the interference condition. The film thickness is set so that the external quantum efficiency is improved by extracting light to the outside without attenuating the light intensity inside the device.

In this way, the optical distance is set so that the external quantum efficiency is maximized by adjusting the film thickness of the transparent conductive film 17, as well as a monochromatic panel or an area color panel that emits light using a monochromatic backlight. It is especially useful in the color panel which employs the color conversion method which receives the light emitted from a monochromatic backlight in a color conversion layer, and converts it into light emission of RGB.

In addition, as one of the practical problems of the organic EL panel, the contrast is lowered by the external light, and it has been found that the cause is that the external light is directly reflected by the metal layer. According to equation (5), the light of the wavelength enhanced by the interference is limited, so that only the light of a specific wavelength is reflected, so that the reflection intensity of light of the wavelength not satisfying the equation (5) is reduced, so that the organic EL of the present invention It turns out that an element contributes also to the contrast improvement of organic electroluminescent panel.

Furthermore, in order to improve the contrast, a transparent conductive film and a metal layer are laminated to form a reflective layer, and the transparent conductive film in the reflective layer is colored with a light emitting color so as to have a structure in which reflection is not possible except for the light emitting color, or the material of the metal layer has a characteristic of absorbing other than the light emitting color. It is effective to make it a material. For this purpose, a method of absorbing light having a wavelength that does not need to be extracted to the outside of the transparent electrode in the laminated portion of the transparent conductive film and the metal layer and a method of absorbing the metal layer material are considered. In this case, it is preferable to configure each layer so that the optical distance of the layer existing between the metal electrode and the light emitting layer satisfies the expression (5), but is not limited thereto.

In particular, in the color conversion type color panel, since the backlight is blue, it is effective to use a metal having a larger reflection coefficient of blue compared to red as the reflective metal. Specifically, Zn, Mo, and Cr may be used. Moreover, the bluening method of a transparent conductive film can be achieved by methods, such as adding only 1% or less of CuO, Co, Ti, to the oxide layer which comprises a transparent conductive film.

The structure of the organic EL element of the present invention may be a structure shown in FIG. 2 in addition to the structure shown in FIG.                 

FIG. 2 is a view for explaining the structure when the lower electrode of the organic EL element is an anode. The metal electrode 28, the anode, the transparent conductive film 27 and the hole injection layer 23 are formed on the substrate 29. The hole transport layer 22, the light emitting layer 24, the electron transport layer 25, the electron injection layer 26, and the transparent electrode 21 which is a cathode are laminated in order. Here, the structure of the electron injection layer 26 and the portion of the transparent electrode 21 serving as the cathode forms the electron injection layer 26 as an ultrathin film of an oxide, fluoride, boride, or chloride of an alkali or alkaline earth metal. A metal ultra thin film such as Al is deposited, and further, an In ₂ O ₃ -ZnO oxide layer (IZO) is disposed thereon, or a transparent electrode 21 made of a transparent oxide such as IZO is directly deposited on the electron injection layer 26. Configuration is contemplated.

On the other hand, the present invention is applicable to all the organic EL devices proposed as conventional organic EL device configurations, such as a configuration without a hole transport layer, in addition to the organic EL devices having a layer structure shown in Figs.

(Example 1)

3 is a cross-sectional view of a color conversion system color panel constructed using the organic EL device of the present invention. On the substrate 301 provided with the TFT 302, Cr (5 nm) / Pt (100 nm) is deposited as a metal electrode 303 as a reflective metal, and In is used as a transparent conductive film 304 as an anode thereon. _A 2O ₃ -ZnO oxide layer (IZO: refractive index 2.2) was deposited. The metal electrode 303 as the reflective metal used herein is not limited to a laminate of Cr / Pt as long as the unevenness is a metal or an alloy that is a conductor of 4 nm or less. In addition, although film formation of IZO is performed by the sputtering method, other film formation methods, such as an electron beam vapor deposition method and a resistive heating vapor deposition method, can also be used.

The hole injection layer 305, the hole transport layer 306, and the light emitting layer 307 are sequentially deposited on the transparent conductive film 304 by resistance heating deposition, and further, Al of 8-hydroxyquinoline as the electron transport layer 308. 20 nm of a complex (Al complex; Alq ₃ ) is laminated.

The stacked portion 309 of the electron injection layer and the upper transparent electrode deposits 0.5 nm of LiF as the electron injection layer, and then deposits 1 nm of Al and 220 nm IZO on the upper transparent electrode, and finally forms SiON as a protective film. It is comprised by depositing 300 nm.

The optical distance of the organic EL element having such a structure is adjusted between the transparent conductive film 304 and the hole injection layer 305 and the hole transport layer 306 and the Pt film constituting the metal electrode 303 of the lower electrode of the anode. It was. Since the wavelength of the color conversion backlight is 470 nm, and the hole injection layer 305 is 80 nm and the hole transport layer 306 is 20 nm, the refractive index of the organic material is 1.85, and the IZO is determined from the interference condition of Equation (5). The film thickness was 183 nm. Furthermore, 0.6% CuO was added to the IZO film, which is the transparent conductive film 304 constituting the lower electrode, and colored blue.

Thus, the protective layer 316 is provided on the element-formed substrate 301, and the gel body 314 is formed in the gap by opposing the substrate 310 on which the RGB color conversion filters 311, 312, and 313 are prepared. In the state of being charged, the element outer peripheral part was sealed with the outer periphery sealing agent 315, and the panel was completed. Here, the color conversion filter means a filter provided with a color filter and / or a fluorescence filter.

As a result of comparing the characteristics of the panel of the configuration shown in this embodiment with the characteristics of the panel of the conventional configuration, the external extraction efficiency can be improved from 2.0% to 3.0%, and the current flowing through the same brightness can be reduced to 2/3. It became possible. Furthermore, the contrast ratio obtained 200: 1 at 100 cd / m 2 under 1000 Lx.

In addition, the same comparative experiment was carried out in a monochrome panel or an area color, and the same result was obtained.

(Example 2)

A transparent conductive film, the film material even if the same comparison as in Example 1 using the In ₂ O ₃ of _{In 2 O 3 -SnO 2 (ITO} ) , instead of the thickness -ZnO 201㎚ (refractive index 2.0), Example The same effect as 1 was obtained. The ITO film can be formed by a method such as sputtering, vapor deposition, or CVD. In addition, the same result was obtained when the optical distance was adjusted using ZnO or SnO ₂ as the transparent conductive film material.

As described above, according to the present invention, a transparent conductive film is disposed on the light emitting layer side of the metal electrode of the organic EL device, and the film thickness of the transparent conductive film is adjusted so that the light reflected from the metal electrode is interfered and strengthened in the device. Therefore, the external quantum efficiency can be improved without accompanying the deterioration of the luminance, and furthermore, the contrast is improved because the metal electrode and the transparent conductive film are adapted to absorb light of a specific wavelength, thereby not involving the deterioration of the luminance. It is possible to provide an organic EL element which can improve the external quantum efficiency and improve the contrast, and an organic EL panel using the same.

Claims (11)

An organic EL device comprising an organic EL light emitting unit including an organic light emitting layer between a metal electrode and a transparent electrode, A transparent conductive film is provided on the side of the organic EL light emitting portion of the metal electrode, 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 light emission wavelength of the organic light emitting layer,

(n = 0, 1, 2, .....) ...................

An organic EL device characterized in that it is set to satisfy. An organic EL device comprising an organic EL light emitting unit including an organic light emitting layer between a metal electrode and a transparent electrode, A transparent conductive film is provided on the side of the organic EL light emitting portion of the metal electrode, The transparent conductive film is colored with a light emitting color to make it impossible to reflect other than the light emitting color, or the material of the metal electrode is selected from a material having a characteristic of absorbing other than the light emitting color, so that light having a wavelength different from that of the organic light emitting layer is emitted from the metal. An organic EL element characterized by absorbing at least one or both of an electrode and the transparent conductive film, and emitting only light having a wavelength emitted from the organic light emitting layer from the transparent electrode. An organic EL device comprising an organic EL light emitting unit including an organic light emitting layer between a metal electrode and a transparent electrode, A transparent conductive film is provided on the side of the organic EL light emitting portion of the metal electrode, 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 light emission wavelength of the organic light emitting layer,

(n = 0, 1, 2, .....) ................

Is set to satisfy The transparent conductive film is colored with a light emitting color to make it impossible to reflect other than the light emitting color, or the material of the metal electrode is selected from a material having a characteristic of absorbing other than the light emitting color, so that light having a wavelength different from that of the organic light emitting layer is emitted from the metal. An organic EL device, which absorbs at least one of an electrode and the transparent conductive film and emits only light having a wavelength emitted from the organic light emitting layer from the transparent electrode. The method according to any one of claims 1 to 3, The transparent conductive film material is an organic EL device, characterized in that at least one of _{In 2 O 3 -ZnO, In 2} O 3 -SnO 2, ZnO, SnO 2. The method of claim 2 or 3, The transparent conductive film is an organic EL device characterized in that an impurity is added and colored with the same color as the light emitted from the organic light emitting layer. The method of claim 5, wherein The organic light emitting layer emits blue light, Composed of the transparent conductive film is CuO, any of the material of the Co or Ti containing any one of the impurity in a concentration of up to 1% of _{In 2 O 3 -ZnO, In 2} O 3 -SnO 2, ZnO, SnO 2 It is An organic EL device characterized in that the transparent conductive film absorbs light other than blue. The method of claim 2 or 3, The organic light emitting layer emits blue light, The metal electrode is made of Zn, Mo, Cr, or an alloy of these metals, and the metal electrode absorbs light other than blue. The organic panel of any one of Claims 1-3 is provided, The monochrome panel characterized by the above-mentioned. An area color panel, comprising the organic EL element according to any one of claims 1 to 3. The organic electroluminescent element of Claim 6, the blue monochromatic backlight, and the color conversion filter are provided, Absorbs light other than blue into the transparent conductive film of the organic EL element, And the blue color monochromatic light from the backlight is reflected by the metal electrode. The organic electroluminescent element of Claim 7, the blue monochromatic backlight, and the color conversion filter are provided, A color conversion type color panel, wherein the metal electrode absorbs light other than blue to reflect only blue monochromatic light from the backlight.

Images