阅读说明：本技术 发光器件及显示面板 (Light emitting device and display panel ) 是由 樊燕 温向敏 于 2021-07-16 设计创作，主要内容包括：本申请总体来说涉及显示技术领域,具体而言,涉及一种发光器件及显示面板,显示面板安装有该发光器件,发光器件包括基板,所述基板形成有发射一种颜色光的像素区,所述像素区包括远离所述基板上的第一电极层、有机功能层、第二电极层及出光层组,所述出光层组包括至少两个折射率不同的耦合层,且相邻两个耦合层之间折射率不同,表面等离子体激元模式的光从低折射率的耦合层传输至高折射率的耦合层后,表面等离子体激元的色散曲线与高折射率耦合层的色散曲线存在交点,实现波矢匹配,在折射率高的耦合层中辐射出光,从而提高耦合出光效率。(This application relates to and shows technical field generally, particularly, relates to a luminescent device and display panel, and this luminescent device is installed to display panel, and luminescent device includes the base plate, the base plate is formed with the pixel district of a transmission colour light, the pixel district is including keeping away from first electrode layer, organic functional layer, second electrode layer and light-emitting layer group on the base plate, the light-emitting layer group includes the coupling layer of two at least refractive index differences, and refractive index difference between two adjacent coupling layers, and the light of surface plasmon polariton mode is transmitted to the coupling layer of high refractive index from the coupling layer of low refractive index after, and there is the nodical in surface plasmon's dispersion curve and the dispersion curve of high refractive index coupling layer, realizes the wave vector and matches, radiates the light-emitting in the coupling layer that the refractive index is high to improve coupling light extraction efficiency.)

1. A light emitting device, comprising a substrate (100), wherein the substrate (100) is formed with a pixel region for emitting light of one color, and the pixel region comprises a first electrode layer (200), an organic functional layer (300), a second electrode layer (400) and a light emitting layer group (500) far away from the substrate (100);

the light-emitting layer group (500) comprises at least two coupling layers with different refractive indexes, and the refractive indexes of the two adjacent coupling layers are different, so that light in a surface plasmon mode is transmitted from the coupling layer with the low refractive index to the coupling layer with the high refractive index to be excited.

2. A light emitting device according to claim 1, wherein the group of light extraction layers (500) comprises a first coupling layer (510) and a second coupling layer (520) having a refractive index smaller than that of the first coupling layer (510);

the second coupling layer (520) is located on the second electrode layer (400), the coverage area of the second coupling layer (520) is smaller than the area of the pixel region, and the first coupling layer (510) covers and wraps the second coupling layer (520).

3. A light emitting device according to claim 2, wherein the second coupling layer (520) is provided in plurality in a same layer spaced apart from each other.

4. A light emitting device according to claim 2, wherein the first coupling layers (510) are disposed in a plurality at intervals on the same layer, the second coupling layer (520) is disposed between two adjacent first coupling layers (510), and each first coupling layer (510) covers and wraps at least one second coupling layer (520).

5. A light emitting device according to claim 1, wherein the light extraction layer group (500) comprises a first coupling layer (510) and a second coupling layer (520) having a smaller refractive index than the first coupling layer (510), the first coupling layer (510) and the second coupling layer (520) being located on the same layer and adjacent to each other.

6. A light emitting device according to claim 5, wherein the first coupling layer (510) and the second coupling layer (520) are alternately arranged in plurality.

7. The light-emitting device according to claim 1, wherein the coupling layers are arranged in a same layer, and refractive indices of the coupling layers are different from each other.

8. A light emitting device according to claim 7, wherein a refractive index of the coupling layer at the edge of the pixel region is greater than a refractive index of an adjacent coupling layer at an inner side thereof.

9. A light emitting device according to claim 1, wherein the second electrode layer (400) comprises a transparent metal electrode.

10. A display panel characterized in that the light-emitting device according to any one of claims 1 to 9 is mounted.

Technical Field

The present application relates generally to the field of display technologies, and in particular, to a light emitting device and a display panel.

Background

Organic Light Emitting Diodes (OLEDs) have been receiving much attention from researchers in recent years in lighting and flat panel display applications due to their advantages of portability, fast response, low operating voltage, wide color gamut, wide viewing angle, high brightness, low power consumption, and the like.

However, a serious problem in the OLED device is that most of the light generated by the active layer of the device is wasted in the surface plasmon mode, and the organic light emitting diode with high coupling light extraction efficiency is always the focus of research in this field.

Disclosure of Invention

In this summary, concepts in a simplified form are introduced that are further described in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

In order to solve the technical problem that light emitted by the existing light emitting device is wasted in a plasmon mode, the main object of the present application is to provide a light emitting device and a display panel.

In order to achieve the purpose of the invention, the following technical scheme is adopted in the application:

a light-emitting device comprises a substrate, wherein a pixel region emitting light of one color is formed on the substrate, and the pixel region comprises a first electrode layer, an organic functional layer, a second electrode layer and a light-emitting layer group which are far away from the substrate;

the light-emitting layer group comprises at least two coupling layers with different refractive indexes, and the refractive indexes of the two adjacent coupling layers are different, so that light in a surface plasmon mode is transmitted from the coupling layer with the low refractive index to the coupling layer with the high refractive index to be excited.

Further, in some embodiments of the present application, the light-emitting layer group includes a first coupling layer and a second coupling layer having a refractive index smaller than that of the first coupling layer;

the second coupling layer is located on the second electrode layer, the coverage area of the second coupling layer is smaller than that of the pixel region, and the first coupling layer covers and wraps the second coupling layer.

Further, in some embodiments of the present application, the second coupling layer is disposed at intervals on the same layer.

Further, in some embodiments of the present application, the first coupling layers are arranged on the same layer at intervals, the second coupling layer is arranged between two adjacent first coupling layers, and each first coupling layer at least covers and wraps one second coupling layer.

Further, in some embodiments of the present application, the light-emitting layer group includes a first coupling layer and a second coupling layer having a refractive index smaller than that of the first coupling layer, and the first coupling layer and the second coupling layer are located on the same layer and are disposed adjacent to each other.

Further, in some embodiments of the present application, the first coupling layer and the second coupling layer are alternately arranged in a plurality.

Further, in some embodiments of the present application, the coupling layers are arranged in the same layer, and refractive indexes of the coupling layers are different.

Further, in some embodiments of the present application, the refractive index of the coupling layer at the edge of the pixel region is greater than the refractive index of the coupling layer adjacent to the inner side of the pixel region.

Further, in some embodiments of the present application, the second electrode layer includes a transparent metal electrode.

A display panel is provided with the above light emitting device.

According to the technical scheme, the light-emitting device and the display have the advantages and positive effects that:

the light-emitting layer group comprises at least two coupling layers with different refractive indexes, the refractive indexes of the two adjacent coupling layers are different, light in a surface plasmon mode is transmitted to the coupling layer with the high refractive index from the coupling layer with the low refractive index and is excited and extracted, namely, the light in the surface plasmon mode is transmitted to the coupling layer with the high refractive index from the coupling layer with the low refractive index, an intersection point exists between a dispersion curve of the surface plasmon and a dispersion curve of the coupling layer with the high refractive index, wave vector matching is realized, light is radiated in the coupling layer with the high refractive index, and therefore the coupling light-emitting efficiency is improved.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and together with the description, serve to explain the principles of the invention.

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without inventive exercise.

Fig. 1 is a schematic diagram illustrating a light extraction layer set including two coupling layers in a light emitting device according to an exemplary embodiment.

Fig. 2 is a schematic diagram illustrating a light emitting device in which two coupling layers are alternately arranged according to an exemplary embodiment.

Fig. 3 is a schematic diagram illustrating an alternative arrangement of a plurality of coupling layers having different refractive indices in a light emitting device according to an exemplary embodiment.

Fig. 4 is a schematic diagram illustrating another structural state in which a light extraction layer group includes two coupling layers in a light emitting device according to an exemplary embodiment.

Fig. 5 is a schematic structural diagram illustrating a light extraction layer group including a plurality of second coupling layers in a light emitting device according to an exemplary embodiment.

Fig. 6 is a schematic view showing another structure of a plurality of coupling layers in a light emitting device according to an exemplary embodiment.

Fig. 7 is a schematic diagram illustrating wave-vector matching of a light emitting device according to an exemplary embodiment.

Wherein the reference numerals are as follows:

100-a substrate; 200-a first electrode layer; 300-an organic functional layer; 400-a second electrode layer; 500-a light extraction layer group; 510-a first coupling layer; 520-a second coupling layer; 530-a third coupling layer; 540-a fourth coupling layer; 550-a fifth coupling layer; 560-sixth coupling layer.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments in the present application are within the scope of the present application without inventive efforts, and therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention but only to represent selected embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Since the organic light emitting diode has many advantages such as lightness, fast response speed, low working voltage, wide color gamut, wide viewing angle, high brightness, low power consumption, etc., in recent years, researchers have drawn extensive attention in illumination and flat panel display applications, however, a very serious problem in the OLED device is that most of the light generated by the active layer of the device is wasted in a surface plasmon mode, and the organic light emitting diode with high coupling light extraction efficiency is always the research focus in this field. In order to solve the technical problem that light emitted by the conventional light emitting device is wasted in a plasmon mode, the present application mainly aims to provide a display panel of a light emitting device, on which the light emitting device is mounted, wherein the light emitting device includes a substrate 100, the substrate 100 is formed with a pixel region for emitting light of one color, the pixel region includes a group of a first electrode layer 200, an organic functional layer 300, a second electrode layer 400 and a light emitting layer 500 far away from the substrate 100, the light emitting layer 500 group includes at least two coupling layers with different refractive indexes, and the refractive indexes between two adjacent coupling layers are different, photons of a surface plasmon mode are transmitted from a coupling layer with a low refractive index to a coupling layer with a high refractive index and are excited and extracted, that is, after the photons of the plasmon mode are transmitted from the coupling layer with the low refractive index to the coupling layer with the high refractive index, an intersection point exists between a dispersion curve of the surface plasmon mode and a dispersion curve of the light emitting layer 500 with the high refractive index, wave vector matching is realized, and light is radiated from the coupling layer with high refractive index, so that the coupling light-emitting efficiency is improved.

Example 1:

with reference to fig. 1 and 7, an embodiment of the present application provides a light emitting device and a display panel, where the light emitting device is mounted on the display panel, the light emitting device includes a substrate 100, a pixel region for emitting light of one color is formed on the substrate 100, the pixel region includes a first electrode layer 200, an organic functional layer 300, a second electrode layer 400, and a light exit layer 500 set far away from the substrate 100, the light exit layer 500 set includes a first coupling layer 510 and a second coupling layer 520 having a refractive index smaller than that of the first coupling layer 510, the first coupling layer 510 and the second coupling layer 520 are located on the same layer and adjacent to each other, so as to divide the pixel region into two light exit regions, the first coupling layer 510 is located in one of the light exit regions, and the second coupling layer 520 is located in the other light exit region.

In this embodiment, a plurality of pixel regions may be formed, each pixel region emits light of only one color, electrons and photons at the top interface of the second electrode layer 400 interact with each other, so that plasmons are formed at the top layer of the second electrode layer 400, a dispersion curve of surface plasmons covering the interface of the second coupling layer 520 does not have an intersection point with a dispersion curve of the second coupling layer 520, the surface plasmons cannot be directly coupled and output, the light in a surface plasmon mode is transmitted from the second coupling layer 520 to the first coupling layer 510, an intersection point exists between the dispersion curve of the surface plasmons and the dispersion curve of the first coupling layer 510, wave vector matching is achieved, light is radiated from the first coupling layer 510, and the coupling light extraction efficiency of the light emitting device is improved.

In the present application, referring to the coordinate system in fig. 1, a direction perpendicular to the interface shown in fig. 1 is defined as a Y-axis, and referring to fig. 7, Kx is a wave vector in the X-direction, ω is an angular frequency, c is a light speed, n is a refractive index, and CPL1 is the first coupling layer 510; CPL2 is the second coupling layer 520, and CPL1 may refer to the coupling layer with the higher refractive index of the two adjacent coupling layers, and CPL2 refers to the coupling layer with the lower refractive index of the two adjacent coupling layers, as understood by those skilled in the art. As can be seen from fig. 7, the dispersion curve of the surface plasmon at the interface of the second coupling layer 520 does not intersect with the dispersion curve of the second coupling layer 520, and when the surface plasmon at the interface of the second coupling layer 520 is transmitted to the first coupling layer 510 and then is coupled to the first coupling layer 510510 has an intersection point, K, of the dispersion curves_XCPL2＝K_SPPAnd wave vector matching is realized, and light is radiated from the first coupling layer 510, so that the coupling light extraction efficiency of the light-emitting device is improved.

In this application, the second electrode layer 400 includes a metal electrode, which may be a transparent metal electrode, the metal electrode may be an anode of the light emitting device, and the anode may also be made of one metal material of aluminum (Al), magnesium (Mg), and silver (Ag), or a mixture of aluminum (Al), magnesium (Mg), and silver (Ag). The organic functional layer 300 is formed on the first electrode layer 200, and the organic functional layer 300 may include a small molecule organic material or a polymer molecule organic material, may be a fluorescent light emitting material or a phosphorescent light emitting material, may emit red light, green light or blue light, or may emit white light, etc., but only one color of light is emitted per pixel region. According to different practical needs, in different examples, the organic functional layer 300 may further include functional layers such as a hole injection layer, a hole transport layer, an organic light emitting layer, an electron transport layer, and an electron injection layer. The second electrode layer 400 covers the organic functional layer 300, and the polarity of the second electrode layer 400 is opposite to that of the first electrode layer 200; the second electrode layer 400 may be a cathode made of a metal material such as lithium (Li), aluminum (Al), magnesium (Mg), or silver (Ag). When a plurality of light emitting devices are formed on the same substrate 100, the first electrode layer 200 may be disconnected, each first electrode layer 200 corresponds to one organic functional layer 300, the second electrode layer 400 may be a full-surface electrode, and the same second electrode layer 400 may correspond to a plurality of organic functional layers 300. It is understood that the light emitting device provided in the embodiments of the present invention may further include, in addition to the above structures, a barrier layer, a buffer layer, a pixel defining layer, a spacer, and an encapsulation layer, which may be prepared by using materials and methods in the related art, and the implementation principle is the same as that of each structure in the related art, and will not be described in detail here.

Example 2:

with reference to fig. 2 and 7, an embodiment of the present application provides a light emitting device and a display panel, where the light emitting device is mounted on the display panel, the light emitting device includes a substrate 100, a pixel region for emitting light of one color is formed on the substrate 100, the pixel region includes a first electrode layer 200, an organic functional layer 300, a second electrode layer 400 and a light emitting layer 500 set far away from the substrate 100, the light emitting layer 500 set includes a plurality of first coupling layers 510 and second coupling layers 520 alternately arranged in the same layer, and a refractive index of the second coupling layers 520 is smaller than that of the first coupling layers 510.

In this embodiment, a plurality of pixel regions may be formed, each pixel region emits light of only one color, electrons and photons at a top interface of the second electrode layer 400 interact with each other, so that surface plasmons are formed on the top layer of the second electrode layer 400, a dispersion curve of the surface plasmons covering the interface of the second coupling layer 520 does not have an intersection with a dispersion curve of the second coupling layer 520, the surface plasmons cannot be directly coupled and output, light in a surface plasmon mode is transmitted from the second coupling layer 520 to the first coupling layer 510, an intersection exists between the dispersion curve of the surface plasmons and the dispersion curve of the first coupling layer 510, wave vector matching is implemented, light is radiated from the first coupling layer 510, so that the light coupling efficiency of the light emitting device is improved, the plurality of first coupling layers 510 and the second coupling layers 520 are alternately arranged, so that the wave vector matching regions are uniformly distributed, and the uniformity of the emergent light is enhanced.

Example 3:

with reference to fig. 3 and 7, an embodiment of the present application provides a light emitting device and a display panel, where the light emitting device is mounted on the display panel, the light emitting device includes a substrate 100, a pixel region for emitting light of one color is formed on the substrate 100, the pixel region includes a first electrode layer 200, an organic functional layer 300, a second electrode layer 400 and a light emitting layer 500 set far away from the substrate 100, the light emitting layer 500 set includes a plurality of coupling layers arranged on the same layer, and refractive indexes of the coupling layers are different, so that a high refractive index is formed between two adjacent coupling layers, and a low refractive index is formed between the two adjacent coupling layers.

The surface plasmon is formed on the coupling layer with the low refractive index, the dispersion curve of the surface plasmon and the dispersion curve of the coupling layer in the area where the surface plasmon is located do not have an intersection point, the surface plasmon cannot be directly coupled and output, and after the light in the surface plasmon mode is transmitted to the coupling layer with the high adjacent refractive index from the coupling layer with the low refractive index, the intersection point exists between the dispersion curve of the surface plasmon and the dispersion curve of the coupling layer with the high adjacent refractive index, so that wave vector matching is realized, and the coupling light extraction efficiency of the light-emitting device is improved.

In this embodiment, the light emitting layer 500 set includes a first coupling layer 510, a second coupling layer 520, a third coupling layer 530, a fourth coupling layer 540, a fifth coupling layer 550, and a sixth coupling layer 560, which are arranged in an array, wherein a refractive index of the first coupling layer 510 is greater than a refractive index of the second coupling layer 520, and a refractive index of the sixth coupling layer 560 is greater than a refractive index of the fifth coupling layer 550, so that the refractive index of the coupling layer near the edge of the pixel region is greater than the refractive index of the coupling layer adjacent to the inner side of the pixel region, and the light emitting effect at the edge of the pixel region is enhanced.

Example 4:

with reference to fig. 4 and 7, an embodiment of the present application provides a light emitting device and a display panel, where the light emitting device is mounted on the display panel, the light emitting device includes a substrate 100, a pixel region for emitting light of one color is formed on the substrate 100, the pixel region includes a first electrode layer 200, an organic functional layer 300, a second electrode layer 400 and a light emergent layer 500 set far away from the substrate 100, the light emergent layer 500 set includes a first coupling layer 510 and a second coupling layer 520, a refractive index of the second coupling layer 520 is smaller than a refractive index of the first coupling layer 510, the second coupling layer 520 is located on the second electrode layer 400, a coverage area of the second coupling layer 520 is smaller than an area of the pixel region, the second coupling layer 520 cannot completely cover the second electrode layer 400, and the first coupling layer 510 covers and wraps the second coupling layer 520, so that a portion of the first coupling layer 510 is located on the second electrode layer 400. Preferably, the coverage area of the first coupling layer 510, the area of the pixel region, and the area of the first electrode layer 200 are the same.

The top interface electrons of the second electrode layer 400 interact with photons, so that surface plasmons are formed on the top layer of the second electrode layer 400, the dispersion curve of the surface plasmons covering the interface of the second coupling layer 520 does not have an intersection point with the dispersion curve of the second coupling layer 520, the surface plasmons cannot be directly coupled and output, light in a surface plasmon mode is transmitted from the second coupling layer 520 to the first coupling layer 510, the intersection point exists between the dispersion curve of the surface plasmons and the dispersion curve of the first coupling layer 510, wave vector matching is realized, light is radiated from the first coupling layer 510, and the coupling light extraction efficiency of the light emitting device is improved.

Referring to fig. 5, in the embodiment of the application, the first coupling layer 510 may further cover and wrap the plurality of second coupling layers 520, the plurality of second coupling layers 520 are arranged at intervals, and a plurality of wave vector matching regions are formed in the first coupling layer 510, so that the light intensity distribution of the pixel region is more uniform.

Referring to fig. 6, in the embodiments of the present application, the light-exiting layer 500 includes a first coupling layer 510 and a second coupling layer 520, the refractive index of the second coupling layer 520 is smaller than the refractive index of the first coupling layer 510, the second coupling layer 520 has two structural forms, the second coupling layer 520 in the first structural form is arranged in a staggered manner with the first coupling layer 510, the second coupling layer 520 in the second structural form is covered and wrapped by the first coupling layer 510, the dispersion curve of the surface plasmons covering the interface of the second coupling layer 520 does not have an intersection with the dispersion curve of the second coupling layer 520, the surface plasmons cannot be directly coupled out, the light in the surface plasmon mode is transmitted from the second coupling layer 520 to the first coupling layer 510, the dispersion curve of the surface plasmons has an intersection with the dispersion curve of the first coupling layer 510, wave-vector matching is achieved, light is radiated at the first coupling layer 510, thereby improving the coupled-out efficiency of the light emitting device. Under the understanding of those skilled in the art, in fig. 6, there are only two coupling layers with different refractive indexes, a coupling layer with a higher refractive index may be defined as a first coupling layer 510, a coupling layer with a lower refractive index may be defined as a second coupling layer 520, the first coupling layer 510 may be provided in plural, the sizes of the plural first coupling layers 510 may be the same, the sizes and the forms of the plural second coupling layers 520 may be the same or different, and the refractive indexes of two adjacent coupling layers may be different, that is, the two coupling layers may be laterally adjacent or vertically adjacent.

In summary, the present application provides a light emitting device and a display panel, the display panel is installed with this light emitting device, the light emitting device has a pixel area, the pixel area can be formed with a plurality ofly, each pixel area only jets out the light of a colour, the pixel area includes first electrode layer 200, organic functional layer 300, second electrode layer 400 and light emitting layer 500 group of keeping away from on the base plate 100, light emitting layer 500 group includes two at least coupled layers, the refracting index between two adjacent coupled layers is different, the structural style of light emitting layer 500 group includes in the scheme of this application:

a: as shown in fig. 1, the light-exiting layer 500 includes a first coupling layer 510 and a second coupling layer 520 having a refractive index smaller than that of the first coupling layer 510, and the first coupling layer 510 and the second coupling layer 520 are disposed on the same layer and adjacent to each other.

b: as shown in fig. 2, the light-exiting layer 500 includes a plurality of first coupling layers 510 and second coupling layers 520 arranged in a staggered manner, and the refractive index of the first coupling layers 510 is greater than that of the second coupling layers 520.

c: as shown in fig. 3, a plurality of coupling layers are arranged in the same layer, the coupling layers have different refractive indexes, and the refractive index of the coupling layer at the edge of the pixel region is greater than that of the coupling layer adjacent to the inner side of the pixel region.

d: as shown in fig. 4 and 5, the light emitting layer 500 includes a first coupling layer 510 and a second coupling layer 520 having a refractive index smaller than that of the first coupling layer 510, the second coupling layer 520 is located on the second electrode layer 400, a coverage area of the second coupling layer 520 is smaller than an area of the pixel region, and the first coupling layer 510 covers and wraps one, two, or a plurality of second coupling layers 520 arranged at intervals on the same layer.

e: as shown in fig. 6, the light extraction layer 500 group includes a first coupling layer 510 and a second coupling layer 520 having a refractive index smaller than that of the first coupling layer 510, the second coupling layer 520 is located on the second electrode layer 400, a coverage area of the second coupling layer 520 is smaller than an area of the pixel region, the first coupling layer 510 covers and wraps one, two or more second coupling layers 520 arranged at intervals on the same layer, the first coupling layers 510 are arranged at intervals on the same layer, and the second coupling layer 520 is arranged between two adjacent first coupling layers 510.

The refractive indexes of two adjacent coupling layers are different on a pixel area emitting the same colored light, surface plasmons are formed on the coupling layers with low refractive indexes, the dispersion curve of the surface plasmons does not have an intersection point with the dispersion curve of the coupling layer in the area where the surface plasmons are located, the surface plasmons cannot be directly coupled and output, after the light in the surface plasmons mode is transmitted to the coupling layer with high adjacent refractive index from the coupling layer with low refractive index, the intersection point exists between the dispersion curve of the surface plasmons and the dispersion curve of the coupling layer with high adjacent refractive index, wave vector matching is achieved, the light in the surface plasmon stereo mode on the top layer of the second electrode layer 400 is extracted, and the coupling light extraction efficiency of the light emitting device is improved.

It is noted that, in this document, relational terms such as "first" and "second," and the like, may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

The foregoing are merely exemplary embodiments of the present invention, which enable those skilled in the art to understand or practice the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the general inventive concept. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.