JP2005129455A - Organic light emitting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic light emitting element having prolonged life time by reducing operating temperature of the element as well as improved light emission efficiency, and emitting white light. <P>SOLUTION: In the organic light emitting element having a plurality of light emitters 27, 37 and 97 provided between a positive electrode 23 and a negative electrode 19, the light emitters 27, 37 and 97 individually emit different colored lights and are laminated in order between the negative electrode 23 and the positive electrode 19. The organic light emitting element emits a variety of colored lights by the effect of laminated light emitters 27, 37 and 97 in response to a supplied voltage, and a current density of a current passing through the element is reduced without reducing an entire luminance. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an organic light emitting device, and more particularly, to an organic light emitting device having an effect of increasing the luminous efficiency and at the same time effectively lowering the temperature of the device and extending its life.

Organic light emitting device (Organic Light Emitting Device, commonly known as OLED) was realized in 1987 by Kodak's CWTang and SAVanslyke by using vacuum vacuum deposition to make Aiq ₃ and HTM2 different structures. It has a self-luminous property, has a high response speed, is thin and light, has a low viewing angle, has a wide viewing angle, has a high illuminance, is full color, and has a simple manufacturing process. Having excellent properties has revolutionized the monitor industry.
Describing the above in more detail, as shown in FIG. 1, a known organic light emitting device 10 is mainly formed with an anode (ITO) 13 having transparent conductivity on a transparent substrate 11 by vacuum deposition, and A hole transmission layer (HTL) 15, a light emitting layer (EML or emitting layer) 17, and a metal cathode 19 are further provided on the anode 13 in order. Is mixed with fluorescent substance D. When a bias voltage of 18 is applied between the anode 13 and the cathode 19, the holes are transmitted from the anode 13 through the hole transmission layer 15 to the light emitting layer 17, and the battery is also opposed to the light emitting layer from the cathode 19. 17 is transmitted. The electrons and holes in the light emitting layer 17 further generate excitons (exciton) by recombination, and when the excitons emit energy and return to the normal state, Emits light, or emits light at a wavelength within a specific range by exciting the mixed fluorescent substance D as an excited state.

The known OLED organic light emitting devices as described above are very convenient because they have the effect of projecting a light source, but the overall luminous efficiency (Yield; cd / A) is increased and the operating temperature of the device is increased. There are still problems to be solved such as effective reduction, white light emission, and problems in extending the life of the device.
Therefore, in view of the above-mentioned drawbacks, the organic light-emitting device of the present invention is provided in order to increase the light emission efficiency and simultaneously reduce the operation temperature of the device to extend the lifetime and to provide a white light source.

  The first conductive layer and the second conductive layer are provided. First, the first conductive layer includes a plurality of light emitters, and the first light emitter is provided on the upper surface of the first conductive layer. In addition, other light emitters are sequentially stacked on the upper surface, the second conductive layer is provided on the upper surface of the Nth light emitter, which is the last layer, and between the first conductive layer. Connect the supply voltage.

  According to the present invention, the operating temperature is lowered while the luminous efficiency is increased, so that the effect of extending the lifetime of the element is obtained, and at the same time, a white light source is successfully provided.

As shown in FIG. 2, in the first embodiment of the present invention, the organic light emitting device (abbreviated as OLED) is an anode (ITO) or the like on the light transmitting substrate 21 by vacuum deposition or sputtering. A conductive layer 23 is formed. A first light emitter (1 ^st emitter) 27 for generating a first colored light source is formed on the upper surface of the anode 23, and a second colored light source is further generated on the upper surface of the first light emitter 27. A second light emitter 37 is formed, and a plurality of light emitters are formed by the method of overlapping in the same manner as described above until reaching the Nth light emitter 97 that generates the Nth colored light source, which is the last one. Further, a second conductive layer (metal such as Al, Mg, Li) is further provided on the upper surface of the Nth light emitter 97, and between the first conductive layer 23 and the second conductive layer 29. Is loaded with voltage 28.

  Since the plurality of light emitters 27, 37, and 97 are sequentially formed between the anode 23 and the cathode 29 in the overlapping manner as described above, each colored light source that is generated similarly has a stacking effect. When the supply voltage 28 is applied, the voltage V received by each of the light emitters 27, 37, and 97 is basically equal, and therefore when the light source generated in the light emitters 27, 37, and 97 is the same color light, The illuminance of the light source projected by increases relatively. Conversely, when the light source generated in each of the light emitters 27, 37, and 97 is one of red, blue, green, etc., a white light source is obtained by mixing them.

逆に本発明において、二層の発光体（２７，３７）を具有する有機発光素子構造（図中の曲線I）においては、同様に必要な発光照度は4150 cd/cm²となり、即ち必要な電圧は10.5V、発光効率が17.13 cd/Aとなり、換算すると得られる電流密度が24.2 mA/ cm²となる。同様に異なる電圧を提供すると、異なる発光照度とこれに相対する発光効率が得られる。この実験結果を以下の表に記す。

上述の表１及び表２の二つの表、及び図３からもわかるように、等しい発光照度の状況下では、本発明の二層の発光体を具有する有機発光素子（P）の発光効率は明らかに公知の単層による有機発光素子（I）のそれよりも高くなっており、即ち有機発光素子の商品化において有利であることが言える。また本発明で使用する電圧の数値はやや高いが、本発明では直列方式で陰極と陽極との間に重ねて設置していることから、素子の電流密度が逆に相対して効果的に下げられており、生ずる熱の問題が解決されて素子の寿命を延長させることに繋がる。 Further, as shown in FIG. 3, when the luminous efficiency is compared in terms of light emission illuminance when the present invention and a known structure are used as a set of experimental models, an organic light emitting device using a known single layer light emitter (FIG. In the middle curve P), the illuminance obtained is 4150 cd / cm ² and the luminous efficiency is 8.11 cd / A when the voltage is 5V. The current density obtained by converting this is 51.2 mA / cm ² . By providing different voltages, different luminous illuminance and luminous efficiency relative to this can be obtained, and the experimental results are shown in the following table.

On the contrary, in the present invention, in the organic light emitting device structure (curve I in the figure) having the two layers of light emitters (27, 37), the necessary illuminance is 4150 cd / cm ² , that is, the necessary light intensity. The voltage is 10.5 V, the luminous efficiency is 17.13 cd / A, and the converted current density is 24.2 mA / cm ² . Similarly, when different voltages are provided, different light emission illuminances and light emission efficiencies relative to them can be obtained. The results of this experiment are shown in the following table.

As can be seen from the two tables in Tables 1 and 2 above and FIG. 3, the luminous efficiency of the organic light emitting device (P) having the two-layered light emitter according to the present invention is as follows under the condition of equal luminous intensity. Obviously, it is higher than that of the known organic light emitting device (I) with a single layer, that is, it can be said that it is advantageous in commercializing the organic light emitting device. In addition, although the numerical value of the voltage used in the present invention is slightly high, in the present invention, the current density of the element is effectively reduced relatively oppositely because it is installed in series between the cathode and the anode. Therefore, the problem of the generated heat is solved and the life of the device is extended.

  As shown in FIG. 4, the second embodiment of the present invention is different from the first embodiment described above in that one light emitting layer forms one light emitter. In addition to the light emitting layer (EMT) 273, the light emitter 27 of the light emitting element 40 is further provided with a hole transmission layer (HTL) 271 and an electron transmission layer (ETL) 275. Similarly, the anode 23 and the cathode 29 are provided. A plurality of light emitters 27, 37, and 97 are provided in this order. Each light emitting body 27 (37, 97) is assembled from a hole transmission layer (HTL) 271 (371, 971), a light emitting layer (EMT) 273 (373, 973), and an electron transmission layer (ETL) 275 (375, 975). Therefore, the same excellent luminous efficiency and life extension effect as those described above can be obtained.

Finally, as shown in FIG. 5, in the third embodiment of the present invention, all the light emitters 27 (37, 97) of the light emitting element 50 are all hole injection layers (HTL) 277 (377, 977), hole transmission. Layer (HTL) 271 (371, 971), electron transmission layer (ETL) 275 (375, 975), and electron injection layer (EIL) 279 (379, 979), which are combined in the same manner as described above. It is provided between the anode 23 and the cathode 29, and due to the stacking effect caused by the stacking, the current density and the temperature are lowered under the same illuminance, and a relatively excellent luminous efficiency and life extension effect are obtained. It is done.
In the above-described embodiment, each of the light emitters 27, 37, and 97 may include a mixture D. The mixture D may be a fluorescent material, a phosphorescent material, or the like, thereby further improving the light emitting effect. Can be.

It is a structural sectional view of a known organic light emitting device. It is sectional drawing of the 1st Example in the organic light emitting element of this invention. It is a table | surface which shows the result of having experimented the organic light emitting element and the well-known structure in this invention with the experimental model. It is sectional drawing of the 2nd Example in the organic light emitting element of this invention. It is sectional drawing of the 3rd Example in the organic light emitting element of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Light emitting element 11 Translucent substrate 13 Anode 15 Hole transmission layer 17 Light emitting layer 18 Voltage supply 19 Cathode 20 Light emitting element 21 Translucent substrate 23 Anode 27 First light emitter 271 Hall transmission layer 273 Light emitting layer 275 Hole transmission layer 277 Hole injection layer 279 Electron injection layer 28 Voltage supply 29 Cathode 37 Second light emitter 371 Hole transmission layer 373 Hole transmission layer 375 Light emission layer 377 Hole injection layer 379 Electron injection layer 40 Light emitting element 50 Light emitting element 97 Nth light emitter 971 Hall transmission layer 973 Light emission Layer 975 Hole injection layer 977 Hole injection layer 979 Electron injection layer

Claims (9)

In the organic light emitting device including the first conductive layer and the second conductive layer,
The first illuminator is provided on the upper surface, and other illuminants are further stacked in order on the upper surface of the first illuminant, and finally the Nth illuminant is provided. One conductive layer;
The second conductive layer provided on the upper surface of the Nth light emitter and applied with a supply voltage between the first conductive layer;
An organic light emitting device comprising:   2. The organic light emitting device according to claim 1, wherein the light emitter is a light emitting layer.   3. The organic light emitting device according to claim 2, wherein the light emitter includes a hole injection layer, a hole transmission layer, an electron transmission layer, an electron injection layer, or a combination thereof.   2. The organic light emitting device according to claim 1, wherein each of the light emitters emits colored light.   5. The organic light-emitting element according to claim 4, wherein the colored lights emitted by the respective light emitters are all equal in color.   The organic light-emitting device according to claim 4, wherein the color of light emitted by each of the light emitters is one of red, blue, green, or a combination thereof.   The organic light emitting device according to claim 1, wherein the organic light emitting device includes a translucent substrate provided on the lower surface of the first conductive layer.   2. The organic light emitting device according to claim 1, wherein a mixture is mixed in each light emitting body of the organic light emitting device.   9. The organic light emitting device according to claim 8, wherein the mixture is one of a fluorescent material, a phosphorescent material, or a combination thereof.

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