CN102664240B - Organic electroluminescent display device and preparation method thereof - Google Patents

Abstract

The invention provides an organic electroluminescent display device and a preparation method thereof. The organic electroluminescent display device comprises a base plate, a transparent medium layer, an anode, a cavity transmission layer, a luminescent layer, an electronic transmission layer and a cathode, wherein spherical grooves which have certain size and are tightly distributed are formed on the transparent medium layer; the index of refraction of each spherical groove is between the index of refraction of a base plate material and the index of refraction of an anode material; and the chord length L of each spherical groove is between 2 mu m and 5 mu m, and the depth H of each spherical groove is between 1 mu m and 3 mu m. By adoption of the structure, the light emergence rate of the device can be improved, so the efficiency of the device is improved.

Description

A kind of organic electroluminescence display device and preparation method thereof

technical field

The invention belongs to the technical field of organic electroluminescence, and in particular relates to an organic electroluminescence display device and a preparation method thereof.

Background technique

Organic electroluminescent devices (OLEDs) have become an increasingly attractive technology for applications such as flat panel displays, lighting, and backlighting due to their advantages such as low driving voltage, solid-state light emission, and flexible displays. Luminous efficiency is an important parameter to characterize the luminous characteristics of OLEDs. The luminous efficiency of an OLED generally refers to the external quantum efficiency ηext of the device, which is mainly determined by the internal quantum efficiency ηint and the light extraction rate ηr (ηext=ηint×ηr). OLEDs with very high internal quantum efficiencies (85%) have been fabricated. The main reason for the low light extraction rate ηr is that light entering a material with a small refractive index from a material with a large refractive index will produce total reflection, so only part of the light exits through the interface.

Contents of the invention

The object of the present invention is to provide an organic electroluminescence display device and its preparation method, the display device has a high light extraction rate.

To achieve the above object, the present invention adopts the following technical solutions:

An organic electroluminescent display device, comprising a substrate, an anode, a hole transport layer, a light-emitting layer, an electron transport layer and a cathode arranged sequentially from bottom to top, a transparent medium layer is arranged between the substrate and the anode, and the transparent medium Spherical or nearly spherical grooves are distributed on the surface of the layer opposite to the anode, and the refractive index of the transparent medium layer is between the substrate and the anode.

The transparent medium layer is a transparent film prepared on the substrate by spin coating or printing.

The groove has a chord length of 2-5 μm and a depth of 1-3 μm.

The grooves are closely arranged.

A method for preparing the above-mentioned organic electroluminescent display device, comprising the following steps:

Spin-coat a processable transparent medium on the cleaned substrate to obtain a transparent film, use silk to rub or roll out spherical or approximate spherical grooves on the surface of the transparent film, and then dry the transparent film, and the transparent film after drying Evaporate the anode material to obtain the anode, evaporate the hole transport layer on the anode, evaporate the light-emitting layer on the hole transport layer, evaporate the electron transport layer on the light-emitting layer, and evaporate the cathode on the electron transport layer, evaporate After the cathode is plated, packaging is carried out to obtain an organic electroluminescent display device.

The transparent medium is transparent resin.

The transparent resin is polyimide.

The organic electroluminescent display device of the present invention changes the shape of the interface between the anode and the organic layer by preparing a transparent medium layer with grooves on the substrate, and reduces the ratio of total reflection of light at the interface between the anode and the organic layer, so The light extraction rate of the organic electroluminescent display device is significantly improved.

Description of drawings

Fig. 1 is a schematic cross-sectional structure diagram of an organic electroluminescent display device according to the present invention;

Fig. 2 is a schematic cross-sectional view of the groove of the present invention;

Fig. 3 is one of the schematic diagrams of the organic electroluminescent display device of the present invention;

Fig. 4 is the second schematic diagram of the organic electroluminescence display device of the present invention;

In the figure: 1. substrate; 2. transparent medium layer; 3. anode; 4. hole transport layer; 5. light emitting layer; 6. electron transport layer; 7. cathode.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and embodiments. It should be noted that the following examples are only used to illustrate the present invention, and are not intended to limit the implementation scope of the present invention.

Referring to FIG. 1 and FIG. 2, the organic electroluminescent display device of the present invention includes a substrate 1, an anode 3, a hole transport layer 4, a light emitting layer 5, an electron transport layer 6 and a cathode 7 arranged sequentially from bottom to top, A transparent medium layer 2 is arranged between the substrate 1 and the anode 3, and spherical or approximately spherical grooves are distributed on the surface of the transparent medium layer 2 opposite to the anode 3, and the refractive index of the transparent medium layer 2 is between that of the substrate. 1 and the anode 3, the transparent medium layer 2 is a transparent film prepared on the substrate 1 by spin coating or printing, which has certain machinability and facilitates the processing of grooves. The grooves are closely arranged, so The chord length of the groove is 2-5 μm, and the depth is 1-3 μm.

The method for preparing the above-mentioned organic electroluminescence display device comprises the following steps:

Spin-coat a machinable transparent medium on the cleaned substrate to obtain a transparent film. The transparent medium is a transparent resin, and the transparent resin is polyimide. Use silk to rub or roll out a spherical or approximate spherical surface on the surface of the transparent film. Then the transparent film is dried, and the anode material (such as aluminum + molybdenum oxide) is evaporated on the dried transparent film to obtain the anode 3, and the hole transport layer 4 is evaporated on the anode 3. The light-emitting layer 5 is evaporated on the layer 4, the electron transport layer 6 is evaporated on the light-emitting layer 5, and the cathode 7 is evaporated on the electron transport layer 6. After the cathode is evaporated, the organic electroluminescent display device is obtained by packaging.

Referring to Figure 3 and Figure 4, θ _c is the critical angle at which light is totally reflected at the interface between the anode and the organic layer (ab in Figure 3). The lengths of both are r, ab is the chord length L of the spherical groove, L=2rsinθ _c , and the depth of the spherical groove H=r(1-cosθ _c ), when the light incident on point a along the horizontal direction, when the incident angle is less than At the critical angle, it is refracted into the substrate glass, and part of the incident light is reflected or refracted by the adjacent spherical groove interface and emerges from the front of the substrate glass. Since the proportion of total reflection of light is reduced, the light extraction efficiency is improved. Usually about 46% of the light energy is consumed in the organic layer/anode. Considering that although the grooves are closely arranged, there are still gaps in the middle, and assuming that all the light entering the glass substrate exits, this structure can increase the light extraction rate by more than 20%. The determination of the chord length and depth is to consider the continuity of film formation and the overall thickness of the organic layer in the device. The chord height is determined to be about 1-3 μm, and the relationship between the chord length and the radius of the arc is determined accordingly.

Setting the transparent medium layer between the substrate and the anode can significantly improve the waveguide effect between the anode and the organic layer. If the transparent medium layer is placed outside the substrate, the waveguide effect between the organic layer and the anode will be improved little. It is conducive to the improvement of the light extraction rate.

Claims (5)

1. prepare a method for organic elctroluminescent device, it is characterized in that: comprise the following steps:

On substrate after cleaning, the machinable transparent medium of spin coating obtains transparent membrane, with silk at transparent membrane mantle friction or the groove rolling out sphere or approximate sphere, then transparent membrane is dried, on transparent membrane after the drying, evaporation anode material obtains anode (3), at the upper evaporation hole transmission layer (4) of anode (3), at the upper evaporation luminescent layer (5) of hole transmission layer (4), at the upper evaporation electron transfer layer (6) of luminescent layer (5), again at the upper evaporation negative electrode (7) of electron transfer layer (6), carry out encapsulation after the complete negative electrode of evaporation and obtain organic elctroluminescent device.

2. a kind of method preparing organic elctroluminescent device according to claim 1, is characterized in that: described transparent medium is transparent resin.

3. a kind of method preparing organic elctroluminescent device according to claim 2, is characterized in that: described transparent resin is polyimides.

4. a kind of method preparing organic elctroluminescent device according to claim 1, is characterized in that: the chord length of described groove is 2-5 μm, and the degree of depth is 1-3 μm.

5. a kind of method preparing organic elctroluminescent device according to claim 1, is characterized in that: described groove close-packed arrays.