KR20070044308A - Top-emitting oled - Google Patents

Abstract

An organic electroluminescent device is provided. The organic light emitting diode has a substrate having a first pixel region. A first anode, which is a light reflection electrode, is positioned on the first pixel region. A first hole injection layer is formed on the first anode using a laser thermal transfer method. A first light emitting layer is positioned on the first hole injection layer. A cathode is positioned on the first light emitting layer.

Organic light emitting device, hole injection layer, laser thermal transfer method

Description

Top-emitting OLED Field Top-emitting OLED

1 is a cross-sectional view showing an organic light emitting display device and a method of manufacturing the same according to an embodiment of the present invention.

2 is a cross-sectional view showing an organic light emitting display device and a method of manufacturing the same according to another embodiment of the present invention.

3 is a graph showing luminance characteristics of organic light emitting diodes according to Experimental Examples and Comparative Examples.

4 is a graph showing current density characteristics of organic light emitting diodes according to Experimental Examples and Comparative Examples.

5 is a graph showing lifespan characteristics of organic light emitting diodes according to Experimental Examples and Comparative Examples.

<Explanation of symbols for main parts of the drawings>

100: substrate 110, 113, 115: anode

110a, 113a, and 115a: reflective films 110b, 113b and 115b: transparent conductive films

120a, 125a: first hole injection layer 120b, 125b: second hole injection layer

125c: third hole injection layer

The present invention relates to an organic light emitting device, and more particularly to a top light emitting organic light emitting device.

In general, the organic light emitting display device is a self-luminous display device, which has a wide viewing angle, excellent contrast, and fast response speed.

A general organic electroluminescent device includes an anode, an organic light emitting layer positioned on the anode, and a cathode located on the organic light emitting layer. When a voltage is applied between the anode and the cathode, holes are injected from the anode into the organic light emitting layer, and electrons are injected from the cathode into the organic light emitting layer. Holes and electrons injected into the organic light emitting layer combine in the organic light emitting layer to generate excitons, and the excitons emit light while transitioning from the excited state to the ground state.

In such an organic light emitting device, the anode is formed to reflect light, that is, the cathode is formed of a transmission type, that is to transmit light, so that the light emitted from the organic light emitting layer to emit light toward the cathode direction It is possible to manufacture a type organic electroluminescent device.

In such a top emission type organic electroluminescent device, a conductive material having an excellent reflection characteristic and an appropriate work function is suitable as the reflective anode, but there is currently no single material that satisfies these characteristics and is applicable. Therefore, the above characteristics are satisfied by forming the reflective anode in a multilayer structure of a reflective film and a transparent conductive film. In this case, an oxide film may be formed between the reflective film and the transparent conductive film due to an oxidation reaction according to a work function difference. The oxide film may interfere with current flow between the reflective film and the transparent conductive film. As a result, a decrease in luminance and a decrease in lifespan of the organic light emitting display device may occur.

The technical problem to be achieved by the present invention is to solve the problems of the prior art, to provide an organic light emitting device having improved brightness and life characteristics.

In order to achieve the above technical problem, the present invention provides an organic light emitting display device. The organic light emitting diode has a substrate having a first pixel region. A first anode, which is a light reflection electrode, is positioned on the first pixel region. A first hole injection layer is formed on the first anode using a laser thermal transfer method. A first light emitting layer is positioned on the first hole injection layer. A cathode is positioned on the first light emitting layer.

The anode may include a double layer of a reflective film and a transparent conductive film. The reflective film may be an aluminum film, a silver film, an aluminum alloy film, or a silver alloy film, and the transparent conductive film may be an ITO film or an IZO film. On the other hand, the cathode is preferably a light transmitting cathode.

The substrate may further include a second pixel area. In this case, a second anode is positioned on the second pixel area. A second hole injection layer is positioned on the first hole injection layer and the second anode. A second light emitting layer is positioned on the second hole injection layer corresponding to the second anode. In this case, the cathode is located on the light emitting layers. Further, the first pixel area is a red pixel area, and the second pixel area is a blue or green pixel area. In addition, the second hole injection layer is preferably formed using a vacuum deposition method or a spin coating method.

Alternatively, the substrate may further include a second pixel region, a second anode may be located on the second pixel region, and a second hole injection layer formed by laser thermal transfer may be located on the second anode. have. In this case, a second light emitting layer is positioned on the second hole injection layer. Furthermore, the substrate further includes a third pixel region, wherein a third anode is positioned on the third pixel region, and a third hole is formed on the first hole injection layer, the second hole injection layer, and the third anode. An injection layer may be positioned, and a third emission layer may be positioned on the third hole injection layer corresponding to the third anode. In this case, it is preferable that the first pixel area is a red pixel area, the second pixel area is a green pixel area, and the third pixel area is a blue pixel area. Further, the first hole injection layer is preferably thicker than the second hole injection layer. In addition, the third hole injection layer is preferably formed using a vacuum deposition method or a spin coating method.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings in order to describe the present invention in more detail. However, the present invention is not limited to the embodiments described herein but may be embodied in other forms. Rather, the embodiments introduced herein are provided to enable the disclosed contents to be thorough and complete, and to fully convey the spirit of the present invention to those skilled in the art. In the figures, where a layer is said to be "on" another layer or substrate, it may be formed directly on the other layer or substrate, or a third layer may be interposed therebetween. Like numbers refer to like elements throughout the specification.

1 is a cross-sectional view showing an organic light emitting display device and a method of manufacturing the same according to an embodiment of the present invention.

Referring to FIG. 1, a substrate 100 having a first pixel area A is provided. The substrate 100 may further include a second pixel area B. FIG. In addition, the substrate 100 may further include a third pixel region C. FIG. The first to third pixel areas A, B, and C may be pixel areas representing different colors.

The first anode 110, the second anode 113, and the third anode 115, which are light reflection electrodes, are formed on the pixel regions A, B, and C, respectively. Each of the anodes 110, 113, and 115, which are the light reflection electrodes, has a double layer of reflective films 110a, 113a, and 115a and transparent conductive films 110b, 113b, and 115b positioned on the reflective films 110a, 113a, and 115a. can do. Furthermore, another transparent conductive film may be further provided below the reflective films 110a, 113a, and 115a. The reflective films 110a, 113a, and 115a may be aluminum films, silver films, aluminum alloy films, or silver alloy films. The aluminum alloy film may be an aluminum neodymium (AlNd) film. In addition, the transparent conductive films 110b, 113b, and 115b may be an indium tin oxide (ITO) film or an indium zinc oxide (IZO) film.

The first hole injection layer 120a is formed on the first anode 110 by using laser induced thermal imaging (LITI). The formation of the first hole injection layer 120a using the laser thermal transfer method will now be described in detail. First, a donor film for forming the first hole injection layer 120a is prepared. The donor film may be prepared by forming a light-to-heat conversion layer on a base film and forming a transfer layer for a hole injection layer on the light-to-heat conversion layer. Subsequently, a donor film having a transfer layer is positioned on the substrate 100 including the anodes 110, 113, and 115 so that the transfer layer faces the substrate 100, and then onto the base film. By irradiating a laser, the transfer layer is transferred onto the first anode 110. As a result, a first hole injection layer 120a is formed on the first anode 110.

Subsequently, a second hole injection layer 120b may be formed on the first hole injection layer 120a, the second anode 113, and the third anode 115. The second hole injection layer 120b may be formed using a vacuum deposition method or a spin coating method. As a result, the second hole injection layer 120b may be formed on all of the pixel areas A, B, and C. The first hole injection layer 120a and the second hole injection layer 120b may be formed using a low molecular material such as CuPc, TNATA, TCTA, or TDAPB and one selected from a polymer material such as PANI and PEDOT.

The first light emitting layer 140A corresponding to the first anode 110, the second light emitting layer 140B corresponding to the second anode 113, and the third anode (on the second hole injection layer 120b) The third light emitting layer 140C is formed at 115. Forming the light emitting layers 140A, 140B, and 140C for each unit pixel region may be performed using a vacuum deposition method or a laser thermal transfer method using a fine metal mask.

Before forming the emission layers 140A, 140B, and 140C, a hole transport layer 130 may be further formed on the second hole injection layer 120b. Forming the hole injection layer 130 is preferably performed using a spin coating method or a vacuum deposition method. As a result, the hole transport layer 130 is formed over all the unit pixel areas of the substrate 100. The hole transport layer 130 may be formed using one selected from a low molecular material such as NPB, NPD, TPD, s-TAD, MTADATA, and a polymer material such as PVK.

The electron transport layer 150 may be formed on the emission layers 140A, 140B, and 140C, and the electron injection layer 160 may be formed on the electron transport layer 150. Alternatively, any one of the electron transport layer 150 and the electron injection layer 160 may be omitted. The electron transport layer 150 may be formed using a polymer material such as PBD, TAZ, spiro-PBD and one selected from a low molecular material such as Alq3, BAlq, SAlq, and the electron injection layer 160 may be formed of Alq3, It can be formed using one selected from gallium mixture (Ga complex), PBD, LiF.

Subsequently, a cathode 170 is formed on the electron injection layer 160. That is, the cathode 170 may be commonly located on the light emitting layers 140A, 140B, and 140C. The cathode 170 is preferably a light transmissive cathode. As a result, the light emitted from the light emitting layers 140A, 140B, and 140C may be emitted to the upper surface of the substrate through the cathode 170. The light transmissive cathode 170 is formed using Mg, Ca, Al, Ag, Ba, or alloys thereof, and is formed to a thickness sufficient to transmit light.

The anodes 110, 113, and 115, the emission layers 140A, 140B, and 140C, the cathode 170, and various organic layers interposed between the anodes 110, 113, 115, and the cathode 170. The fields 120a, 120b, 130, 150, and 160 form an organic light emitting display device.

By forming the first hole injection layer 120a on the first anode 110 using a laser thermal transfer method, the driving voltage, the luminous efficiency of the organic light emitting diode formed on the first pixel region A, Current density and lifespan can be improved. This is caused by the destruction of the oxide film formed between the reflective film 110a and the transparent conductive film 110b due to heat generated during the formation of the first hole injection layer 120a using the laser thermal transfer method. In the process of forming the first hole injection layer 120a by using a laser thermal transfer method, due to the improvement of the interface property between the first anode 110, which is the light reflection film, and the first hole injection layer 120a. I can guess.

Furthermore, a first hole injection layer 120a is formed on the first anode 110, and on the first hole injection layer 120a, the second anode 113, and the third anode 115. By forming the second hole injection layer 120b, an optical path between the first light emitting layer 140A and the first anode 110, in detail, an optical path between the first light emitting layer 140A and the reflective film 110a is formed. The optical path between the second light emitting layer 140B and the reflective film 113a or the optical path between the third light emitting layer 140C and the reflective film 115a may be formed longer. In this case, the first light emitting layer 140A may be a red light emitting layer. In addition, any one of the second emission layer 140B and the third emission layer 140C may be a green emission layer, and the other may be a blue emission layer. That is, the first pixel area A may be a red pixel area, one of the second pixel area B and the third pixel area C may be a green pixel area, and the other may be a blue pixel area. Can be. As a result, in the case of red light having a long optical wavelength, the light path can be formed long, and as a result, the color purity of the red organic light emitting diode can be improved.

In this case, the thickness of the first hole injection layer 120a is n / 2 times the wavelength at which the optical distance between the first light emitting layer 140A and the reflective film 110a is emitted from the first light emitting layer 140A ( n is an integer). As a result, color purity of the red organic light emitting diode can be optimized.

In addition, by forming the second hole injection layer 120b on the entire surface of the substrate by spin coating or vapor deposition, the hole injection layers of all the pixel regions are more easily compared to the case of patterning by laser thermal transfer. Different optical paths may be formed for each device.

2 is a cross-sectional view showing an organic light emitting display device and a method of manufacturing the same according to another embodiment of the present invention. The organic light emitting display device according to the present exemplary embodiment may be the same as the organic light emitting display device described with reference to FIG. 1 except for the following description.

Referring to FIG. 2, a substrate 100 having a first pixel area A and a second pixel area B is provided. The substrate 100 may further include a third pixel region C. The first to third pixel areas A, B, and C may be pixel areas representing different colors.

The first anode 110, the second anode 113, and the third anode 115, which are light reflection electrodes, are formed on the pixel regions A, B, and C, respectively.

The first hole injection layer 125a is formed on the first anode 110 by using laser induced thermal imaging (LITI). In addition, the second hole injection layer 125b is formed on the second anode 113 by using a laser thermal transfer method. The first hole injection layer 125a and the second hole injection layer 125b may be formed to have different thicknesses.

Subsequently, a third hole injection layer 125c may be formed on the first hole injection layer 125a, the second hole injection layer 125b, and the third anode 115. The third hole injection layer 125c may be formed using a vacuum deposition method or a spin coating method. As a result, the third hole injection layer 125c may be formed on all of the pixel areas A, B, and C.

The first light emitting layer 140A corresponding to the first anode 110, the second light emitting layer 140B corresponding to the second anode 113, and the third anode (on the third hole injection layer 125c) The third light emitting layer 140C is formed at 115.

Before forming the light emitting layers 140A, 140B, and 140C, a hole transport layer 130 may be further formed on the third hole injection layer 125c.

The electron transport layer 150 may be formed on the emission layers 140A, 140B, and 140C, and the electron injection layer 160 may be formed on the electron transport layer 150. Alternatively, any one of the electron transport layer 150 and the electron injection layer 160 may be omitted. Subsequently, a cathode 170 is formed on the electron injection layer 160.

The anodes 110, 113, and 115, the emission layers 140A, 140B, and 140C, the cathode 170, and various organic layers interposed between the anodes 110, 113, 115, and the cathode 170. The fields 125a, 125b, 125c, 130, 150, and 160 form an organic light emitting display device.

The first pixel is formed on the first anode 110 and the second anode 113 by forming the first hole injection layer 125a and the second hole injection layer 125b by using a laser thermal transfer method. The driving voltage, the luminous efficiency, the current density and the lifespan characteristics of the organic light emitting diodes formed on the region A and the second pixel region B can be improved.

Further, the first hole injection layer 125a and the second hole injection layer 125b are formed on the first anode 110 and the second anode 113, respectively, and the first hole injection layer ( 125a), a third hole injection layer 125c is formed on the second hole injection layer 125b and the third anode 115 to form a gap between the first light emitting layer 140A and the first anode 110. In detail, the optical path between the first light emitting layer 140A and the reflective film 110a and the optical path between the second light emitting layer 140B and the reflective film 113a may be defined as the third light emitting layer 140C. It may be formed longer than the optical path between the reflective film (115a). In this case, the first light emitting layer 140A may be a red light emitting layer, the second light emitting layer 140B may be a green light emitting layer, and the third light emitting layer 140C may be a blue light emitting layer. That is, the first pixel area A may be a red pixel area, the second pixel area B may be a green pixel area, and the third pixel area C may be a blue pixel area.

Preferably, the thickness of the first hole injection layer 125a is made larger than the thickness of the second hole injection layer 125b, so that the longer the light wavelength, the longer the light path can be. The color purity of each organic light emitting diode can be improved.

In this case, the thickness of the first hole injection layer 125a is n / 2 times the optical distance between the first light emitting layer 140A and the reflective film 110a is emitted from the first light emitting layer 140A ( n is an integer), and the thickness of the second hole injection layer 125b is a wavelength at which the optical distance between the second light emitting layer 140B and the reflective film 113a is emitted from the second light emitting layer 140B. It is preferable to form so as to be n / 2 times (n is an integer). As a result, color purity of the red and green organic light emitting diodes may be optimized.

Hereinafter, preferred examples are provided to aid the understanding of the present invention. However, the following experimental examples are only for helping understanding of the present invention, and the present invention is not limited to the following experimental examples.

Experimental Example 1

(1) Fabrication of Red Organic Light Emitting Diode

ITO was used on the substrate to form an anode having an area of 2 mm x 2 mm, which was subjected to ultrasonic cleaning and UV-O ₃ treatment. A hole injection layer having a thickness of 600 μs was formed on the UV-O ₃ treated anode by using a laser thermal transfer method. At this time, the scanning speed of the laser was 0.8 m / s. The hole injection layer was formed using TDATA (4,4 ', 4 "-Tris (N, N-diphenyl-amino) -triphenylamine). Α-NPB (N, N'-Bis) on the hole injection layer (naphthalen-1-yl) -N, N'-bis (phenyl) benzidine) was vacuum-deposited to a thickness of 300 kPa to form a hole transport layer, wherein an aromatic amine host and an iridium complex were used as a dopant on the hole transport layer. A red light emitting layer was formed by vacuum evaporation to a thickness of 300 GPa, and an electron transport layer was formed by vacuum evaporation of Alq3 to a thickness of 300 GPa on the light emitting layer, Mg and silver were co-deposited on the electron transport layer. A cathode was formed by forming a magnesium-silver film having an atomic ratio of silver of 10: 1 and a thickness of 100 GPa, thereby producing a red organic electroluminescent device.

(2) Measurement of driving voltage and luminous efficiency

In driving the organic light emitting diode, after applying a positive voltage to the anode and grounding the cathode, the light emission luminance of the organic light emitting diode was measured by a photometer. The organic electroluminescent device had a voltage at a luminance of 400 cd / m 2, that is, a driving voltage of 5.37 V. In addition, the luminous efficiency was 8.61 cd / A. The luminance characteristics are shown in FIG. 3, and the current density characteristics are shown in FIG. 4.

(3) Measurement of Accelerated Life Characteristics

After driving the organic light emitting diode to have an initial brightness of 400 cd / m 2 (relative brightness 100), the degree of decrease in luminance was measured according to the driving time. This is shown in FIG. 5.

(4) color coordinate measurement

The color coordinates of the organic light emitting device were measured using a color analyzer. The result was a color coordinate of (0.69, 0.31).

Experimental Example 2

(1) Fabrication of Red Organic Light Emitting Diode

In forming the hole injection layer, an organic light emitting diode was manufactured according to the same method as Experimental Example 1 except that the scanning speed of the laser was 0.75 m / s.

(2) Characteristic evaluation

As a result of measurement in the same manner as in Experimental Example 1, the voltage when the luminance was 400 cd / m 2, that is, the driving voltage was 5.44 V, the luminous efficiency was 8.26 cd / A, and the color coordinates were (0.69, 0.31). The luminance characteristics are shown in FIG. 3, the current density characteristics are shown in FIG. 4, and the acceleration life characteristics are shown in FIG. 5.

Comparative Example

(1) Fabrication of Red Organic Light Emitting Diode

An organic light emitting diode was manufactured according to the same method as Experimental Example 1 except that the hole injection layer was formed by using the vacuum deposition method.

(2) Characteristic evaluation

As a result of measurement in the same manner as in Experimental Example 1, the voltage when the luminance was 400 cd / m 2, that is, the driving voltage was 6.30 V, the luminous efficiency was 7.9 cd / A, and the color coordinates were (0.69, 0.31). The luminance characteristics are shown in FIG. 3, the current density characteristics are shown in FIG. 4, and the acceleration life characteristics are shown in FIG. 5.

The driving voltages, luminous efficiency and color coordinate characteristics of the organic light emitting diodes according to the experimental examples and the comparative example are summarized in Table 1 below.

Drive voltage (V @ 400cd / ㎡) Luminous Efficiency (cd / A) Color coordinates (X, Y) Experimental Example 1 5.37 8.61 (0.69, 0.31) Experimental Example 2 5.44 8.26 (0.69, 0.31) Comparative example 6.30 7.9 (0.69, 0.31)

Referring to Table 1, when the hole injection layer is formed using the laser thermal transfer method (Experimental Example 1 and Experimental Example 2) compared to the case of forming the hole injection layer using the vacuum deposition method (Comparative Example) It can be seen that the light emission efficiency characteristics are reduced and the light emission efficiency is improved.

3 to 5, when the hole injection layer is formed using the laser thermal transfer method (Experimental Example 1 and Experimental Example 2), compared to the case of forming the hole injection layer using the vacuum deposition method (Comparative Example). ) Can be seen that the brightness, current density and life characteristics are improved.

According to the present invention as described above, by forming the hole injection layer on the anode by using a laser thermal transfer method, it is possible to improve the driving voltage, luminous efficiency, current density and lifetime characteristics of the organic light emitting device. Further, by forming a first hole injection layer on one anode and a second hole injection layer on the first hole injection layer and the other anode, it is possible to optimize the color purity of the organic light emitting device.

Claims (14)

A substrate having a first pixel region; A first anode disposed on the first pixel region and being a light reflection electrode; A first hole injection layer disposed on the first anode and formed using a laser thermal transfer method; A first light emitting layer on the first hole injection layer; And An organic light emitting device comprising a cathode located on the first light emitting layer. The method of claim 1, And the anode comprises a double layer of a reflective film and a transparent conductive film. The method of claim 2, The reflective film is an organic light emitting display device, characterized in that the aluminum film, silver film, aluminum alloy film or silver alloy film. The method of claim 2, The transparent conductive film is an organic electroluminescent device characterized in that the ITO film or IZO film. The method of claim 1, The substrate further includes a second pixel region, A second anode positioned on the second pixel region; A second hole injection layer positioned on the first hole injection layer and the second anode; And a second light emitting layer disposed on the second hole injection layer corresponding to the second anode. The method of claim 5, And the cathode is located on the light emitting layers. The method of claim 5, And the first pixel area is a red pixel area, and the second pixel area is a blue or green pixel area. The method of claim 5, The second hole injection layer is an organic light emitting display device, characterized in that formed using a vacuum deposition method or spin coating method. The method of claim 1, The substrate further includes a second pixel region, A second anode positioned on the second pixel region; A second hole injection layer on the second anode and formed by laser thermal transfer; The organic light emitting device of claim 2, further comprising a second light emitting layer on the second hole injection layer. The method of claim 9, The substrate further includes a third pixel region, A third anode positioned on the third pixel region; A third hole injection layer positioned on the first hole injection layer, the second hole injection layer, and the third anode; And a third light emitting layer on the third hole injection layer corresponding to the third anode. The method of claim 10, And the first pixel area is a red pixel area, the second pixel area is a green pixel area, and the third pixel area is a blue pixel area. The method of claim 11, wherein The first hole injection layer is an organic light emitting device, characterized in that thicker than the second hole injection layer. The method of claim 10, The third hole injection layer is formed using a vacuum deposition method or a spin coating method. The method of claim 1, The cathode is an organic light emitting device, characterized in that the light transmitting cathode.

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