WO2016010172A1

WO2016010172A1 - Organic light-emitting diode having improved light extraction efficiency

Info

Publication number: WO2016010172A1
Application number: PCT/KR2014/006377
Authority: WO
Inventors: 이학규
Original assignee: (주)켐옵틱스
Priority date: 2014-07-15
Filing date: 2014-07-15
Publication date: 2016-01-21
Also published as: KR20160008797A

Abstract

The present invention relates to an organic light-emitting diode (OLED) and, more specifically, to an OLED having improved light extraction efficiency without performance deterioration of elements by minimizing absorption, reflection, and a waveguide phenomenon of light according to the differences in refractive indexes of stacked elements.

Description

Organic light emitting device with improved light extraction efficiency

The present invention relates to an organic light emitting diode (OLED), and more particularly, to an organic light emitting diode having improved light extraction efficiency without degrading device performance by minimizing light absorption, reflection, and waveguide phenomena due to the difference in refractive index of stacked devices. It is about.

An organic electric device refers to a device capable of inducing a flow of electric charge between a pole and an organic material using holes and / or electrons. According to the principle of operation, the exciton formed in the organic material layer is separated into electrons and holes by photons introduced into the device from an external light source, and the separated electrons and holes are transferred to different electrodes to be used as current sources. There is an electronic device of the type which is to inject holes and / or electrons to the organic material by applying a voltage or current to the two or more electrodes of the form, and operates by the injected electrons and holes. Examples of organic electronic devices include organic light emitting diodes (OLEDs), organic solar cells, organic photoconductor (OPC) drums or organic transistors.

The organic light emitting device refers to a self-luminous device using an electroluminescence phenomenon that emits light when a current flows through the light emitting organic compound. Organic light emitting devices are attracting attention as next-generation materials in various industrial fields such as displays and lighting because of their advantages of excellent thermal stability and low driving voltage. However, total reflection occurs in the process of the light generated from the inside of the stack structure of the device, which causes the internal light extraction efficiency of the device to decrease. Research to increase the internal light extraction efficiency has been continuously made.

FIG. 1 is a schematic view showing a laminated structure of a substrate 10 for a general organic light emitting device. As shown in the drawing, the substrate 10 includes a transparent electrode 12 made of an anode to supply a current to the organic light emitting layer 13, which is a light emitter, and a cathode 14 having one surface of the organic light emitting layer 13. And is placed in the form of a sandwich on the other side. The transparent electrode 12 positioned on one side of the organic light emitting layer 13 in a direction in which light is emitted uses a conventional transparent electrode ITO for transmitting light. In addition, a glass substrate 11 is used on one side of the transparent electrode 12 to stack the transparent electrode 12, the organic light emitting layer 13, and the cathode 14. In this case, an interface exists between the glass substrate 11, the transparent electrode 12, the organic light emitting layer 13, and the cathode 14, which are stacked, and the first boundary surface L1 and the second boundary surface (from one side to the other direction). L2) and the third boundary surface L3.

In this case, the refractive index of the organic light emitting layer 13 is typically 1.7 to 1.8, the refractive index of the transparent electrode 12 is about 1.95, and the refractive index of the glass substrate 11 is about 1.5. Therefore, since the refractive indices of the elements constituting each layer are different from each other, the reflections from the difference in the refractive indices on the first to third interfaces L1, L2, and L3, the layers absorbed by the elements constituting each layer, and the layers having high refractive index As a result, a waveguide phenomenon in which light is trapped is generated, and the light extraction efficiency of the light emitted from the organic light emitting layer 13 is reduced.

In particular, since the transparent electrode 12 has a higher refractive index than the glass substrate 11 on one side and the organic light emitting layer 13 on the other side, a waveguide phenomenon occurs in which light generated in the organic light emitting layer 13 is trapped on the transparent electrode 12. The amount of light transmitted to the substrate 11 is reduced, which is a major cause of impairing the light extraction efficiency.

2 is a schematic view showing a laminated structure of a substrate 20 for a conventional organic light emitting device for solving the above-described problems. As shown in the drawing, the substrate 20 includes a glass substrate 21, a light extraction layer 25, a transparent electrode 22, an organic light emitting layer 23, and a cathode 24, which are stacked. The first boundary surface L1, the fourth boundary surface L4, the fifth boundary surface L5, and the third boundary surface L3 are distinguished from one side to another in order.

The substrate 20 is basically a concave-convex 21a on the other surface of the glass substrate 21 using a micro lens array or the like to prevent reflection of light due to the difference in refractive index between the air layer (refractive index 1.0) and the glass substrate 21. To form. Therefore, the light scatters while passing through the unevenness 21a to reduce the difference in refractive index between the air layer and the glass substrate 21 and to prevent the reflection of light at the first interface L1.

In addition, the substrate 20 may additionally have a light extraction layer having a refractive index of about 1.85, which is about the middle of the refractive index of each of the glass substrate 21 and the transparent electrode 22 between the glass substrate 21 and the transparent electrode 22. Insertion of 25 reduces light reflection due to the difference in refractive index on the fourth boundary surface L4 or the fifth boundary surface L5, resulting in improved light extraction efficiency than the substrate 10 shown in FIG. . However, since the refractive index of the transparent electrode 22 layer is the highest, the waveguide phenomenon of the transparent electrode 22 layer cannot be prevented, and thus there is a limitation in improving the light extraction efficiency.

3 is a schematic view showing a laminated structure of a substrate 30 for an organic light emitting device according to another conventional embodiment for solving the above-described problems. As shown in the drawing, the substrate 30 includes a glass substrate 31, a light extraction layer 35, a transparent electrode 32, an organic light emitting layer 33, and a cathode 34, which are stacked between them. The first boundary surface L1, the sixth boundary surface L6, the seventh boundary surface L7, and the third boundary surface L3 are divided in order from one side to the other side.

The illustrated substrate 30 also applies the unevenness 31a on the glass substrate 31, and has a refractive index of about 1.95 so that the refractive index between the glass substrate 31 and the transparent electrode 32 is larger than that of the transparent electrode 32. The light extraction layer 35 is inserted to prevent the waveguide phenomenon of the transparent electrode 32 layer, thereby improving light extraction efficiency. However, since the difference in refractive index between the glass substrate 31 and the light extraction layer 35 becomes larger, the efficiency decrease due to the reflection of light on the sixth interface is inevitably accompanied.

Accordingly, there is a need for the development of an organic light emitting device that improves light extraction efficiency by minimizing light reflection and waveguide phenomenon of a transparent electrode layer according to a difference in refractive index of each layer of stacked layers.

The present invention has been made to solve the above problems, an object of the present invention, by applying a plurality of light extraction layer having a refractive index optimized for reflection of light and prevention of waveguide phenomenon between the glass substrate and the transparent electrode An organic light emitting device having improved extraction efficiency is provided.

According to the present invention, a glass substrate, a transparent electrode of an anode disposed on the other surface of the glass substrate, an organic light emitting layer disposed on the other surface of the transparent electrode, and a cathode disposed on the other surface of the organic light emitting layer are laminated. In an organic light emitting device, the organic light emitting device, the first light extraction layer disposed between the glass substrate and the transparent electrode; And a second light extraction layer disposed between the first light extraction layer and the transparent electrode. The refractive index of the second light extraction layer is higher than the refractive index of the transparent electrode, the refractive index of the first light extraction layer is lower than the refractive index of the transparent electrode and higher than the refractive index of the glass substrate.

In this case, the first light extraction layer, the scattering layer is applied to the scattering particles on one surface of the other surface of the glass substrate abuts; It includes, the other surface abuts one surface of the second light extraction layer is made of a flat surface.

The second light extracting layer may include an adhesive layer for bonding the first light extracting layer and the transparent electrode.

In addition, the first light extraction layer, the refractive index is characterized in that the average value of the refractive index of the glass substrate and the refractive index of the transparent electrode.

In another embodiment, the first light extraction layer is characterized in that the refractive index is the average value of the refractive index of the glass substrate and the refractive index of the second light extraction layer.

The organic light emitting device of which the light extraction efficiency of the present invention is improved by the above configuration is excellent in light extraction efficiency without degrading the performance of the device. In addition, the flatness of the light extraction layer is excellent, there is an effect of excellent uniformity of light emission. In addition, since it does not deviate significantly from the existing manufacturing process, the process and material cost are low, and mass production is easy.

1 is a schematic view showing a laminated structure of a general organic light emitting device

2 is a schematic view showing a laminated structure of a conventional organic light emitting device

3 is a schematic view showing a laminated structure of another organic light emitting diode according to another embodiment

4 is a schematic view showing the laminated structure of the organic light emitting device of the present invention

1000: organic light emitting device

100: glass substrate

200: transparent electrode

300: organic light emitting layer

400: cathode

500: first light extraction layer 510: scattering layer

600: second light extraction layer

L10: first boundary surface L20: second boundary surface

L30: third boundary surface L40: fourth boundary surface

L50: fifth boundary surface

Hereinafter, an embodiment of the present invention as described above will be described in detail with reference to the accompanying drawings.

4 is a schematic view showing a laminated structure of an organic light emitting device 1000 according to an embodiment of the present invention. As shown, the organic light emitting diode 1000 includes a glass substrate 100, a transparent electrode 200 of an anode, an organic light emitting layer 300, and a cathode 400, and additionally includes a first light extracting layer 500 and a first light extracting layer 500. It further comprises two light extraction layer (600).

The organic light emitting device 1000 has a glass substrate 100, a first light extraction layer 500, a second light extraction layer 600, a transparent electrode 200, an organic light emitting layer 300, and a cathode 400 from one side to the other side. ) Are sequentially stacked. Hereinafter, the boundary layer formed between the air and the glass substrate 100 is the first boundary layer L10, and the boundary layer formed between the glass substrate 100 and the first light extraction layer 500 is the second boundary layer L20 and the first light. The boundary layer formed between the extraction layer 500 and the second light extraction layer 600 is the third boundary layer L30, and the boundary layer formed between the second light extraction layer 600 and the transparent electrode 200 is the fourth boundary layer L40. ), A boundary layer formed between the transparent electrode 200 and the organic light emitting layer 500 is defined as a fifth boundary layer L50.

Herein, the glass substrate 100, the transparent electrode 200, the organic light emitting layer 300, and the cathode 400 may be similarly applied to the organic light emitting diode OLED. Is omitted.

The first light extracting layer 500 is disposed between the glass substrate 100 and the second light extracting layer 600, and reduces the difference in refractive index between the glass substrate 100 and the transparent electrode 200 to reflect the light. Configured to minimize. Therefore, the refractive index of the first light extracting layer 500 is larger than the refractive index of the glass substrate 100 and smaller than the refractive index of the transparent electrode 200. More preferably, it may be configured similarly to the average value of the refractive index of the glass substrate 100 and the refractive index of the transparent electrode 200. For example, when the refractive index of the glass substrate 100 is 1.5 and the refractive index of the transparent electrode 200 is 1.95, the refractive index of the first light extraction layer 500 is formed to exceed 1.5 and less than 1.95, more preferably. May be formed between 1.65 and 1.85. When the refractive index of the first light extracting layer 500 is less than 1.65, a difference in refractive index with the transparent electrode 200 increases, causing a problem in that light extraction efficiency due to reflection of light in the third boundary layer L30 is reduced. In addition, when the refractive index of the first light extracting layer 500 exceeds 1.85, the difference in refractive index with the glass substrate 100 becomes large, so that the light extraction efficiency due to the reflection of light in the second boundary layer L20 is deteriorated. Occurs.

In another embodiment, the refractive index of the first light extraction layer 500 may be configured to be similar to the average value of the refractive index of the glass substrate 100 and the refractive index of the second light extraction layer 600. For example, when the refractive index of the glass substrate 100 is 1.5 and the refractive index of the second light extraction layer 600 is 2.0, the refractive index of the first light extraction layer 500 is formed to be greater than 1.5 but less than 2.0. More preferably, it may be formed between 1.7 and 1.9.

As the refractive index difference between the glass substrate 100 and the transparent electrode 200 is reduced through the first light extraction layer 500 as described above, the reflection of the light transmitted from the transparent electrode 200 to the glass substrate 100 is minimized. There is an advantage that the light extraction efficiency is improved.

In addition, a scattering layer 510 to which scattering particles are applied may be formed on one surface of the first light extracting layer 500 that contacts the other surface of the glass substrate 100. The scattering layer 510 is formed in an uneven shape according to the application of the scattering particles, and in order to minimize the reflection of light due to the difference in refractive index at the first interface L10 between the air layer (refractive index 1.0) and the glass substrate 100. It is composed. Therefore, since the light reflection of the first boundary surface L10 is minimized through the first light extraction layer 500, a separate process example for preventing the reflection of the light of the first boundary surface L10 on the glass substrate 100 will be described. For example, there is an advantage that can eliminate the irregular shape processing process.

In addition, a flat surface may be formed on the other surface of the first light extraction layer 500 which is in contact with one surface of the second light extraction layer 600. As the flat surface is formed on the other surface of the first light extraction layer 500, the light uniformity of the light is excellent by preventing scattering of light transmitted from the transparent electrode 200.

The second light extracting layer 600 is disposed between the first light extracting layer 500 and the transparent electrode 200 to minimize the waveguide phenomenon in which light is trapped on the transparent electrode 200. Therefore, the refractive index of the second light extracting layer 600 is larger than the refractive index of the transparent electrode 200. For example, when the refractive index of the transparent electrode 200 is 1.95, the refractive index of the second light extraction layer 600 is configured to exceed 1.95, and more preferably, may be formed between 2.0 and 2.05. If the refractive index of the second light extracting layer 600 is less than 2.0, the waveguide phenomenon suppression effect is insignificant. If the refractive index of the second light extracting layer 600 is greater than 2.05, the difference in refractive index with the transparent electrode 200 is increased, and the light according to the reflection of light at the fourth boundary surface L40 is obtained. There arises a problem that the extraction efficiency is lowered.

Since the refractive index of the second light extracting layer 600 is greater than the refractive index of the transparent electrode 200, the light transmitted through the fifth interface L50 in the organic light emitting layer 300 is not trapped in the transparent electrode 200. Instead of being transmitted to the second light extraction layer 600, the light extraction efficiency is improved.

In addition, the second light extracting layer 600 may be configured to bond the first light extracting layer 500 and the transparent electrode 200 through the second light extracting layer 600 by using an adhesive layer having the aforementioned refractive index. . Through the above configuration, the manufacturing process is simplified and the manufacturing cost is reduced.

In particular, as the second light extraction layer 600 is formed of an adhesive layer, one surface of the second light extraction layer 600 may be molded into a flat surface shape corresponding to the other surface of the first light extraction layer 500, and the second The other surface of the light extraction layer 600 may be molded into a flat surface shape corresponding to one surface of the transparent electrode 200, thereby preventing the scattering of light transmitted from the transparent electrode 200 to prevent the second light extraction layer ( There is an advantage that the light emission uniformity of the light passing through 600 is excellent.

The technical spirit should not be interpreted as being limited to the above embodiments of the present invention. Various modifications may be made at the level of those skilled in the art without departing from the spirit of the invention as claimed in the claims. Therefore, such improvements and modifications fall within the protection scope of the present invention as long as it will be apparent to those skilled in the art.

Claims

In an organic light emitting device, a glass substrate, a transparent electrode of an anode disposed on the other surface of the glass substrate, an organic light emitting layer disposed on the other surface of the transparent electrode, and a cathode disposed on the other surface of the organic light emitting layer are laminated. In

The organic light emitting device,

A first light extracting layer disposed between the glass substrate and the transparent electrode; And

A second light extracting layer disposed between the first light extracting layer and the transparent electrode; Including;

The refractive index of the second light extraction layer is higher than the refractive index of the transparent electrode, the refractive index of the first light extraction layer is lower than the refractive index of the transparent electrode and higher than the refractive index of the glass substrate, the organic light emitting device with improved light extraction efficiency.
The method of claim 1,

The first light extraction layer,

A scattering layer having scattering particles coated on one surface of the glass substrate abutting the other surface thereof; A light emitting efficiency improved organic light emitting device comprising a.
The method of claim 2,

The first light extraction layer,

The organic light emitting device of which the light extraction efficiency is improved, the other surface of which the one surface of the second light extraction layer is in contact with the flat surface.
The method of claim 3, wherein

The second light extraction layer,

An organic light emitting device having an improved light extraction efficiency, comprising an adhesive layer for bonding the first light extraction layer and the transparent electrode.
The method of claim 1,

The first light extraction layer,

The refractive index is an average value of the refractive index of the glass substrate and the refractive index of the transparent electrode, light extraction efficiency improved organic light emitting device.
The method of claim 1,

The first light extraction layer,

The refractive index is an average value of the refractive index of the glass substrate and the refractive index of the second light extraction layer, characterized in that the light extraction efficiency improved organic light emitting device.