TW201929216A - Light emitting device - Google Patents

Abstract

A light emitting device including a first electrode, a second electrode, a light emitting structure, a bank structure, and a reflecting layer is provided. The second electrode is disposed on the first electrode. The light emitting structure is disposed between the first electrode and the second electrode. The bank structure is disposed on the first electrode, and the bank structure surrounds the second electrode and the light emitting structure. The reflecting layer having an opening which exposed the second electrode is disposed on the second electrode.

Description

Light emitting element

The present invention relates to a light emitting element, and more particularly to a light emitting element having a reflective layer disposed on a light emitting structure.

With the advancement of science and technology, flat panel displays are the most noticeable display technology in recent years. Among them, organic light emitting diodes (OLEDs) are self-emitting, have no viewing angle dependence, save power, have simple manufacturing processes, low cost, Low temperature operating range and high response speed have great application potential, and it is expected to become the mainstream of next-generation flat panel displays.

Ink jet printing (IJP) technology can improve material utilization to reduce costs in the OLED manufacturing process, but before inkjet coating, a bank corresponding to the pixel settings needs to be formed to define each One pixel area. However, when liquid droplets are sprayed into the accommodating space formed by the retaining wall, the difference between the surface tension of the liquid and the adhesion of the retaining wall causes the thickness uniformity of the film formed by the subsequent drying process to be poor, resulting in Brightness and chromaticity are significantly different from the center.

Therefore, how to improve the brightness and chromaticity around the pixels when the uniformity of the film thickness is not good is obviously different from the center, which is one of the problems that the current R & D personnel want to solve.

The invention provides a light-emitting element having uniform brightness and chromaticity.

The invention provides a light-emitting element, which includes a first electrode, a second electrode, a light-emitting structure, a retaining wall structure, and a reflective layer. The second electrode is disposed on the first electrode. The light emitting structure is disposed between the first electrode and the second electrode. The retaining wall structure is disposed on the first electrode, and the retaining wall structure surrounds the second electrode and the light emitting structure. The reflective layer is disposed on the second electrode, and the reflective layer has an opening exposing the second electrode.

Based on the above, in the light-emitting element of the present invention, since the reflective layer is disposed on the second electrode and it has an opening exposing the second electrode, the light generated by the light-emitting structure can be made to the reflective layer by means of total reflection. After mixing evenly, shoot out from the same opening again. In this way, even if the brightness and chromaticity around the pixel are significantly different from the center (caused by poor film flatness), the light with different brightness and chromaticity can still be carried out under the reflective layer by means of total reflection. Mix uniformly, so that the light-emitting element has uniform brightness and chromaticity.

In order to make the above features and advantages of the present invention more comprehensible, embodiments are hereinafter described in detail with reference to the accompanying drawings.

Hereinafter, the present invention will be explained more fully with reference to the drawings of this embodiment. However, the present invention may be embodied in various forms and should not be limited to the embodiments described herein. The thicknesses of layers and regions in the drawings are exaggerated for clarity. The same or similar reference numbers indicate the same or similar elements, and the following paragraphs will not repeat them one by one. In addition, the directional terms mentioned in the embodiments, such as: up, down, left, right, front, or rear, are only directions referring to the attached drawings. Therefore, the directional terms used are used to illustrate and not to limit the present invention.

FIG. 1 is a schematic diagram of a light emitting device according to an embodiment of the present invention. It should be noted that, in order to clearly show the path of light passing between the reflective layer and the first electrode, the optical matching layer is omitted in FIG. 1. Fig. 2 is a schematic cross-sectional view taken along the dashed line A-A 'in Fig. 1. It should be noted that, in order to clearly indicate the relative positions of the film layers in the light-emitting element, the film surface differences or thickness differences of the film layers are not shown in FIG. 2.

Please refer to FIG. 1 and FIG. 2 at the same time. The light emitting device 100 includes a first electrode 102, a second electrode 104, a light emitting structure 106, a retaining wall structure 108, and a reflective layer 110. In this embodiment, the light emitting element 100 may include an organic light emitting diode.

The first electrode 102 is disposed on the substrate S. The material of the substrate S may be glass, quartz, organic polymers, opaque / reflective materials (for example, conductive materials, metals, wafers, ceramics, or other applicable materials) or other applicable materials. If a conductive material or metal is used, an insulating layer (not shown) is covered on the substrate S to avoid short-circuit problems. In some embodiments, the substrate S may further include an active device array (not shown), wherein the above active device array includes a plurality of transistors (not shown), which are respectively electrically connected to the corresponding first electrodes 102. . The material of the first electrode 102 is a conductive material such as aluminum (Al), silver (Ag), chromium (Cr), copper (Cu), nickel (Ni), titanium (Ti), molybdenum (Mo), and magnesium (Mg). , Platinum (Pt), gold (Au), or a combination thereof. The first electrode 102 may have a single-layer, double-layer, or multilayer structure. For example, the first electrode 102 may be a three-layer structure composed of Ti / Al / Ti or a three-layer structure composed of Mo / Al / Mo and ITO / Ag / ITO. In some embodiments, the first electrode 102 includes a reflective electrode, and a material thereof may be a metal having good reflectivity to visible light, such as aluminum, molybdenum, gold, or a combination thereof. In some embodiments, the method for forming the first electrode 102 may be chemical vapor deposition (CVD), physical vapor deposition (PVD), atomic layer deposition (ALD), evaporation (VTE), sputtering (SPT), or Its combination. In some embodiments, the first electrode 102 may be an anode of the light emitting element 100.

The second electrode 104 is disposed on the first electrode 102. The material of the second electrode 104 may be a transparent conductive material, such as a metal oxide such as indium tin oxide, indium zinc oxide, aluminum tin oxide, aluminum zinc oxide, or indium germanium zinc oxide. In some embodiments, the method for forming the second electrode 104 may be chemical vapor deposition (CVD), physical vapor deposition (PVD), atomic layer deposition (ALD), evaporation (VTE), sputtering (SPT), or Its combination. In some embodiments, the second electrode 104 may be a cathode of the light emitting element 100.

The light emitting structure 106 is disposed between the first electrode 102 and the second electrode 104. The light emitting structure 106 includes a hole injection layer HIL, a hole transport layer HTL, a light emitting layer EL, and an electron transport layer ETL. The material of the hole injection layer HIL is, for example, xylylene blue copper, star-shaped aromatic amines, polyaniline, polyethylene dioxythiophene, or other suitable materials. The material of the hole transport layer HTL is, for example, triarylamines, cross-structured diamine biphenyls, diamine biphenyl derivatives, or other suitable materials. The light-emitting layer EL may be a red organic light-emitting pattern, a green organic light-emitting pattern, a blue organic light-emitting pattern, or a light-emitting pattern of different colors (for example, white, orange, yellow, and the like) generated by mixing light of each spectrum. The material of the electron transport layer ETL may be an oxazole derivative and its dendrimer, a metal chelate (for example, Alq3), an azole compound, a diazaanthracene derivative, a silicon-containing heterocyclic compound, or other suitable materials. In this embodiment, the first electrode 102 is an anode; the second electrode is a cathode; the light emitting structure 106 includes the above-mentioned hole injection layer HIL, hole transport layer HTL, light emitting layer EL, and electrons in order from the first electrode 102. Transport layer ETL.

In this embodiment, in order to improve the utilization rate of materials to reduce the manufacturing cost of the light emitting device 100, the hole injection layer HIL, the hole transport layer HTL, and the light emitting layer EL may be formed by an inkjet coating process; and electron transmission The layer ETL is formed on the light-emitting layer EL by a thermal evaporation process to reduce the driving voltage of the light-emitting element 100. Based on the difference between the surface tension of the liquid and the adsorption force of the side wall of the retaining wall, the thickness of the light-emitting structure 106 formed by the above process may gradually increase as the thickness of the light-emitting structure 106 increases from the center of the liquid droplet drying process. . In some embodiments, the hole injection layer HIL, the hole transport layer HTL, the light emitting layer EL, and the electron transport layer ETL can also be formed by an inkjet coating process.

The retaining wall structure 108 is disposed on the first electrode 102, and the retaining wall structure 108 surrounds the second electrode 104 and the light emitting structure 106. Before the light-emitting structure 106 is formed by the inkjet coating process, the area of each pixel must be defined by the retaining wall structure 108, and then each film layer in the above-mentioned light-emitting structure 106 is sequentially sprayed on the retaining wall structure. The accommodating space 108a formed by 108. In some embodiments, the retaining wall structure 108 may be a hydrophobic material, for example, a negative photoresist containing fluorine is used as a material, and is formed by processes such as yellow light lithography. In this way, the liquid that is inkjet-coated in the accommodating space 108a can be well fixed therein.

The reflective layer 110 is disposed on the second electrode 104, and the reflective layer 110 has an opening 110 a that exposes the second electrode 104. In this way, the light generated by the light emitting structure 106 can be uniformly mixed under the reflective layer 110 in a total reflection manner, and then emitted through the same opening 110a to be transmitted to the viewer O. In this way, even if the brightness and chrominance around the pixel PX (the part adjacent to the retaining wall structure 108) are significantly different from its center, the light with different brightness and chrominance can still be reflected on the reflective layer 110 by means of total reflection. The light-emitting element 100 has uniform brightness and chromaticity. For example, the thickness of the light emitting structure 106 at the position P1 and the position P2 is different. Therefore, when the same unit area of current is injected, the light produced by the light emitting structure 106 also has different brightness and chromaticity, but the two can be totally reflected by Method (paths L1 and L2 through which light travels as shown in FIG. 1) are uniformly mixed under the reflective layer 110, and then emitted through the opening 110a, so that the pixels PX have uniform brightness and chromaticity. In other words, the pixel PX can maintain the original brightness and chromaticity under the same current per unit area of the light emitting element 100 without being affected by the poor flatness of the film surface, so that the light emitting element 100 has a good life. And efficiency performance. In some embodiments, the light generated at the position P2 has a shorter wavelength than the light generated by the light emitting structure 106 at the position P1.

In some embodiments, the opening 110 a is disposed in the center of the light emitting structure 106. In this way, since the central surface of the light emitting structure 106 is relatively flat, when light exits there and passes through the second electrode 104, it is less susceptible to the influence of uneven thickness. In addition, the size and shape of the opening 110a can be appropriately adjusted according to the design, as long as the light generated by the light emitting structure 106 can pass through the opening 110a.

In some embodiments, an optical matching layer 112 (as shown in FIG. 2) may be selectively provided between the reflective layer 110 and the second electrode 104 to increase the light extraction rate. For example, the optical matching layer 112 may be a refractive index matching layer.

3 is a schematic diagram of a light-emitting element according to another embodiment of the present invention. The light-emitting element 200 is substantially the same as the light-emitting element 100. The difference is that the first electrode 202 of the light-emitting element 200 has an uneven microstructure 202a, so it is the same or similar. The components use the same or similar reference numerals. The connection relationships, materials, functions and processes of the remaining components have been described in detail in the foregoing, so they will not be repeated here.

Referring to FIG. 3, the light-emitting element 200 includes a first electrode 202, a second electrode 104, a light-emitting structure 106, a retaining wall structure 108, and a reflective layer 110.

In this embodiment, the first electrode 202 has a concavo-convex microstructure 202a on a surface adjacent to the light emitting structure 106, and the concavo-convex microstructure 202a is disposed near the retaining wall structure 108 (at the edge of the pixel PX). In this way, in addition to the light at the edge of the pixel PX, it can be concentrated between the reflective layer 110 and the first electrode 202 in the opening 110a in a total reflection manner, and it can also allow the light at the edge to be reflected by the concave-convex microstructure 202a. Scattering, thereby helping the light at the edges to pass to the center of the pixel PX, so that the pixel PX has more uniform brightness and chromaticity. In this embodiment, the concave-convex microstructure 202 a may be composed of a plurality of circular protrusions (as shown in FIG. 3), but the present invention is not limited thereto. In other embodiments, the concave-convex microstructure 202a may also be composed of other protrusions with different shapes or numbers. In some embodiments, part of the concave-convex microstructure 202 a may be disposed in the retaining wall structure 108.

4 is a schematic diagram of a light-emitting element according to another embodiment of the present invention. The light-emitting element 300 is substantially the same as the light-emitting element 100. The difference is that the retaining wall structure 308 of the light-emitting element 300 has a reflective structure 308a, so the same or similar elements The same or similar reference numerals are used. The connection relationship, materials, functions and processes of the remaining components have been described in detail in the foregoing, so they will not be repeated hereafter.

Referring to FIG. 4, the light-emitting element 300 includes a first electrode 102, a second electrode 104, a light-emitting structure 106, a retaining wall structure 308, and a reflective layer 110.

In this embodiment, the retaining wall structure 308 has a reflective structure 308a disposed therein. In this way, in addition to the light at the edge of the pixel PX can be concentrated between the reflective layer 110 and the first electrode 202 in the opening 110a in a total reflection manner, it can also allow the lateral light to be reflected by the reflective structure 308a. Reflected back to the center of the pixel PX to reduce the loss of light, so that the pixel PX has more uniform brightness and chromaticity. In some embodiments, the material of the reflective structure 308a may be a metal, such as Al, Ag, Cr, Cu, Ni, Ti, Mo, Mg, Pt, Au, or a combination thereof. In addition, in other embodiments, the surface of the first electrode 102 may optionally have a concave-convex microstructure (as shown in FIG. 3, the concave-convex microstructure 202 a), and the concave-convex microstructure may be disposed adjacent to the retaining wall structure 108. (At the edge of the pixel PX). The concave-convex microstructure is constituted by a plurality of circular protrusions (as shown in FIG. 3), but the present invention is not limited thereto.

In summary, in the light-emitting element of the above embodiment, since the reflective layer is disposed on the second electrode and has an opening exposing the second electrode, the light generated by the light-emitting structure can be made by total reflection. After uniformly mixing under the reflective layer, it is emitted from the same opening. In this way, even if the brightness and chromaticity around the pixel are significantly different from the center (caused by poor film flatness), the light with different brightness and chromaticity can still be carried out under the reflective layer by means of total reflection. Mix uniformly, so that the light-emitting element has uniform brightness and chromaticity.

Although the present invention has been disclosed as above with the examples, it is not intended to limit the present invention. Any person with ordinary knowledge in the technical field can make some modifications and retouching without departing from the spirit and scope of the present invention. The protection scope of the present invention shall be determined by the scope of the attached patent application.

100, 200, 300‧‧‧ light-emitting elements

102、202‧‧‧First electrode

104‧‧‧Second electrode

106‧‧‧light emitting structure

108, 308‧‧‧ Retaining wall structure

108a‧‧‧accommodation space

110‧‧‧Reflective layer

110a‧‧‧ opening

112‧‧‧Optical matching layer

202a‧‧‧ Bump Microstructure

308a‧‧‧Reflective structure

S‧‧‧ substrate

HIL‧‧‧ Hole injection layer

HTL‧‧‧ Hole Transmission Layer

EL‧‧‧Light-emitting layer

ETL‧‧‧Electronic Transmission Layer

O‧‧‧ viewers

PX‧‧‧Pixels

P1, P2‧‧‧Position

L1, L2‧‧‧ Light route

FIG. 1 is a schematic diagram of a light emitting device according to an embodiment of the present invention. Fig. 2 is a schematic cross-sectional view taken along the dashed line A-A 'in Fig. 1. FIG. 3 is a schematic diagram of a light emitting device according to another embodiment of the present invention. FIG. 4 is a schematic diagram of a light emitting device according to another embodiment of the present invention.

Claims (10)

A light-emitting element includes: a first electrode; a second electrode disposed on the first electrode; a light-emitting structure disposed between the first electrode and the second electrode; a retaining wall structure disposed on the first electrode; On the first electrode, and the retaining wall structure surrounds the second electrode and the light-emitting structure; and a reflective layer is disposed on the second electrode, and the reflective layer has an opening exposing the second electrode. The light-emitting element according to item 1 of the scope of patent application, wherein the thickness of the light-emitting structure increases as it moves away from the center of the light-emitting structure. The light-emitting element according to item 2 of the scope of patent application, wherein the opening is provided at the center of the light-emitting structure. The light-emitting element according to item 1 of the application, wherein the first electrode includes a reflective electrode. The light-emitting element according to item 4 of the application, wherein the first electrode has a concave-convex microstructure on a surface adjacent to the light-emitting structure, and the concave-convex microstructure is disposed at a position adjacent to the retaining wall structure. The light-emitting element according to item 1 of the patent application scope further includes: a reflective structure disposed in the retaining wall structure. The light-emitting element according to item 1 of the patent application scope further includes: an optical matching layer disposed between the reflective layer and the second electrode. The light-emitting element according to item 1 of the scope of patent application, wherein the light-emitting structure includes a hole injection layer, a hole transport layer, a light-emitting layer, and an electron transport layer in order from the first electrode, and the electricity The hole injection layer, the hole transport layer, and the light emitting layer are formed by an inkjet coating process. The light-emitting element according to item 1 of the patent application scope, wherein the light-emitting element includes an organic light-emitting diode. The light-emitting element according to item 1 of the patent application scope, wherein the retaining wall structure comprises a hydrophobic material.