KR20150120837A - Method for manufacturing inverted oled - Google Patents

Abstract

The present invention relates to a method for manufacturing an inverted OLED. The method for manufacturing an inverted OLED comprises the following steps: providing a substrate, and preparing an ITO thin film on the substrate to be a negative electrode; performing plasma immersion ion implantation on the ITO thin film and, at the same time, applying a pulse negative bias to the ITO thin film to make the plasma be injected into the ITO thin film according to a predetermined injection depth; forming organic layers including an electron injection layer, an electron transport layer, a luminescent layer, and a hole transport layer, through a film forming process sequentially on the ITO thin film; and forming a positive electrode through the film forming process on the organic layers. According to the present invention, plasma is injected into an ITO thin film or within a predetermined depth below the surface, thus components exhibit high stability. By using the method of the present invention, an ITO thin film with a lower work function can be obtained; and the transparency and electrical conductivity of the ITO thin film can be maintained. In addition, OLED components manufactured with the ITO thin film processed by using the present invention, as a negative electrode, can have effectively enhanced light-emitting efficiency and component stability.

Description

METHOD FOR MANUFACTURING INVERTED OLED BACKGROUND OF THE INVENTION [0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to OLED display technology, and more particularly, to a method of manufacturing a reverse structure OLED.

In the field of display technology, OLED elements, or "inverted OLEDs (i OLEDs)" have been developed with the continuous development of science and technology, and the device structure is opposite to that of normal devices. Among these, the iolED's generic name is Inverted Organic Light-Emitting Diode.

1, a transparent anode ITO film 92 (Indium Tin Oxide) is first formed on a substrate 91, and film-forming is carried out in that order on the substrate 91 to form a hole transport layer (EIL) and a cathode 97 are formed on the transparent electrode layer 93 (HTL), the light emitting layer 94, and the electron transport layer 95 (ETL). A voltage is loaded from the outside to inject electrons from the cathode, holes are injected from the anode ITO, and light is emitted by exciting organic molecules through complex and complex in the light emitting layer. Since EIL and anode materials used in general OLEDs are materials with low work function and high air activity such as alkali metals (lithium, cesium, barium) and aluminum, they are affected by oxygen gas and moisture in the atmosphere, Resulting in deterioration. Therefore, products using conventional OLEDs should be sealed with glass and adhesive to protect the common OLED electron injection layer and cathode in the display from the effects of atmospheric moisture and oxygen gases, and even high-order hard packing materials . This is one of the high cost elements of OLED displays and OLED lighting fixtures, and is also a major obstacle in realizing soft displays and lighting fixtures.

The structure of the reverse-structured OLED is opposite to that of the general OLED structure, as shown in Fig. The reverse structure OLED uses ITO as a cathode. First, a cathode ITO film 98 is formed on a substrate 91, and then an electron injection layer 96, an electron transport layer 95, A light emitting layer 94 and a hole transporting layer 93 are formed, and finally a cathode 99 is formed. The electron injection layer (EIL) material of the iOLED has improved luminescence efficiency compared to the general structure of the OLED device, and the resistance to oxygen gas and moisture of the iOLED is much higher than that of the OLED of the general structure. This is because the bottom emission type iOLED uses ITO as a cathode so that if an EIL stacked on the ITO cathode can use an inert material, it can realize an OLED device of anaerobic and water resistance and also reduce the necessity of using a high-order hard packing material It is because. Thus, compared to conventional OLEDs, iOLED significantly improved the atmospheric stability and luminous efficiency of the cathode.

In OLED parts, electrons are injected from a cathode to an organic material. The injection efficiency of electrons is determined by the lowest unoccupied molecular orbital (LUMO), which is the energy level of the organic material and the work function of the cathode It is decided. In other words, as the work function of the cathode approaches the LUMO energy level, the injection efficiency of the electrons becomes higher, the electron injection efficiency becomes higher, and the driving voltage required is also smaller, so that the parts can save electricity. In a general situation, the LUMO energy levels of the organic materials are all much lower than the work function of the cathode, and according to the conventional practice in the industry, some organic materials with a relatively high LUMO are found and matched with the cathode, It has too high disadvantage.

The biggest challenge in the current iOLED research process is to lower the work function of ITO for the cathode in iOLED. When ITO is used as a transparent cathode, it is generally very difficult to inject electrons directly from the ITO to the organic layer. This is because the energy difference between the value of the ITO work function and the LUMO energy level accepting the organic layer electrons is relatively large. Since the work function of ITO is about 5 eV and the LUMO energy of an electron transporting material for a general OLED device is about 3 eV, there is an electron injection barrier of about 2 eV on the surface.

In the case of using the ITO according to the conventional method as the cathode, the electron injection efficiency can be effectively improved only by the presence of the electron injection layer of more layers. However, this method causes complicated and costly problems in the process. Therefore, in order to reduce the use of the electron injection layer, the work function of ITO must be reduced as much as possible. At present, the method of reducing the ITO surface work function is to lower the work function of the ITO surface by improving the oxygen vacancies of the ITO surface using a hydrogen plasma surface treatment method. However, this method only improves the surface of the ITO and easily becomes ineffective, resulting in instability of the part. Another method is to add a metal having high activity in the manufacturing process of ITO, for example, a Cs element. This method can reduce the work function of ITO, but the introduction of Cs element causes other good performance of ITO, For example, transparency and the like are severely influenced, which is disadvantageous to the output of light.

Therefore, effectively lowering the work function of ITO for the cathode in reverse-structured OLEDs is becoming a new challenge in this area.

It is an object of the present invention to provide a method of manufacturing an inverse OLED having a work function capable of effectively reducing an ITO anode work function.

According to another aspect of the present invention, there is provided a method of manufacturing an ITO thin film, comprising the steps of providing a substrate and forming an ITO thin film on the substrate to form a cathode; plasma impingement ion implantation is performed on the ITO thin film; The method comprising the steps of: injecting a plasma into the ITO thin film according to a predetermined depth of implantation by applying a bias to the ITO thin film; and forming a film on the ITO thin film in order to form an electron injection layer, an electron transport layer, Forming an organic layer, and forming an anode through film forming in the organic layer.

The present invention is further directed to a method of manufacturing a reverse structure OLED according to the present invention, which includes controlling the depth of implantation of the plasma by adjusting the size of the pulse side bias, controlling the injection density of the plasma by controlling the intensity of the plasma, do.

Advancing the method for manufacturing a reverse structure OLED according to the present invention, the implantation depth of the plasma is 1 to 2 nm.

A further refinement of the method of manufacturing a reverse structure OLED according to the present invention is that the plasma is generated by a hydrogen atom or by a low work function metal atom.

In a further aspect of the method for producing a reverse structure OLED according to the present invention, the metal atom of the low work function is a lithium atom, a magnesium atom, or a cesium atom.

인 바, 즉 산소 빈자리의 농도가 높을 수록, 상기 계산공식에 따른 비율이 더욱 작고, 이의 일함수도 더욱 작다. 따라서, 한편으로, 본 발명은 ITO박막 내에 수소 원자에 의해 생성된 플라즈마를 주입하여 ITO박막 내에서 대량의 H－O결합을 형성함으로써 ITO 표면의 산소 빈자리 농도를 향상시키고 ITO의 일함수를 효과적으로 감소시킨다. 또한, 만일 수소 원자에 의해 생성된 플라즈마를 ITO 표면에만 주입시키면 쉽게 이탈되므로, 수소 원자에 의해 생성된 플라즈마를 ITO 표면 및 표면 이하의 일정한 심도 내로 주입시킨다. 플라즈마는 ITO 표면 내에 속박될 수 있으므로, 표면에만 주입된 경우에 비하여 이탈이 어려워짐으로써 더욱 높은 안정성을 실현할 수 있는 동시에 산소 빈자리를 향상시키는 작용이 쉽게 실효되지 않는다. 다른 한편으로, ITO박막 내에 낮은 일함수의 금속 원자에 의해 생성된 플라즈마를 주입시킴으로써 역시 ITO의 일함수를 감소시킬 수 있고 또한 음극 표면의 전자 농도를 향상시킬 수 있어, 전자의 주입 효율을 효과적으로 향상시킬 수 있다. 또한 전체 ITO 내에 모두 낮은 일함수의 금속 원자에 의해 생성된 플라즈마를 주입시킬 경우 전체 ITO박막의 투명성이 떨어지게 된다. 따라서, 낮은 일함수의 금속 원자에 의해 생성된 플라즈마를 ITO표면 및 표면 이하의 일정한 심도 내로 주입시킴으로써 ITO박막의 전기 전도성을 증가시킬 수 있는 동시에 ITO박막의 투명성에 영향을 미치지 않게 된다.According to the method for fabricating a reverse structure OLED according to the present invention, plasma infiltration ion implantation is performed at a predetermined depth below the surface and the surface of the ITO thin film, and the injected plasma is generated by a hydrogen atom or a low work function metal atom , And the calculation formula relating to the work function of ITO and the concentration of oxygen vacancies therein is

The higher the concentration of oxygen vacancy, that is, the concentration of oxygen vacancy, the smaller the ratio according to the above calculation formula and the smaller the work function thereof. The present invention, on the other hand, improves the oxygen vacancy concentration on the ITO surface and effectively reduces the work function of ITO by forming a large amount of H-O bonds in the ITO thin film by injecting a plasma generated by the hydrogen atom in the ITO thin film . In addition, if a plasma generated by a hydrogen atom is injected only into the ITO surface, it is easily released, so that the plasma generated by the hydrogen atom is injected into the ITO surface and a certain depth below the surface. Since the plasma can be confined in the ITO surface, it is more difficult to separate the plasma than when it is injected only on the surface, so that higher stability can be realized and the function of improving the oxygen vacancy can not easily be lost. On the other hand, by injecting a plasma generated by a metal atom having a low work function in the ITO thin film, the work function of ITO can be reduced and the electron concentration on the surface of the cathode can be improved, . In addition, when a plasma generated by a metal atom having a low work function is injected into the entire ITO, the transparency of the entire ITO thin film is deteriorated. Therefore, by injecting the plasma generated by the metal atom having a low work function into the ITO surface and a certain depth below the surface, the electrical conductivity of the ITO thin film can be increased, and the transparency of the ITO thin film is not affected.

The method of manufacturing a reverse structure OLED according to the present invention has the following advantageous effects.

1) PIII technology is a cost-effective, easy-to-operate, large-area processing technology and is well suited for industrial applications.

2) Utilizing the method of the present invention, a low work function ITO thin film can be obtained and the transparency and electrical conductivity of the ITO thin film can be maintained.

3) Since the plasma is injected into the ITO thin film, the stability of the effect of the modification can be improved.

4) When OLED parts are manufactured using the ITO processed by the method of the present invention as a cathode, it is possible to effectively improve the outgoing light efficiency and the stability of parts.

1 is a structural explanatory view of a conventional OLED.
2 is a structural explanatory view of a conventional inverse OLED.
3 is a flow chart of a method of manufacturing a reverse structure OLED according to the present invention.
4 is a structural explanatory view of a reverse structure OLED manufactured by applying the method according to the present invention.
FIG. 5 is a view illustrating an example in which plasma is injected into the ITO surface and a certain depth below the surface in the method of manufacturing the reverse structure OLED according to the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. It is to be understood that the specific embodiments described herein are for interpretation of the invention only and are not intended to be limiting of the invention.

Referring to FIGS. 3 and 4, FIGS. 3 and 4 are flow charts of a method of manufacturing a reverse structure OLED according to the present invention,

A step of providing a substrate 10 and forming an ITO thin film 20 on the substrate as a cathode (S101); plasma impurity ion implantation (abbreviated as PIII) on the ITO thin film 20; (S102) the plasma is injected into the ITO thin film (20) according to a predetermined depth of implantation by applying a pulse negative bias to the ITO thin film (20) (S103) of forming an organic layer including an electron injection layer (30), an electron transport layer (40), a light emitting layer (50) and a hole transport layer (60) via a film forming process (S104). ≪ / RTI >

Hereinafter, the present invention will be described with reference to specific embodiments.

Example 1

이다. 즉, 산소 빈자리의 농도가 높을 수록, 해당 계산공식의 값은 더욱 작고, 그 일함수도 더욱 작다. 따라서, 플라즈마 잠입 이온주입 방식을 이용하여 수소 원자에 의해 생성된 이온을 ITO표면 및 표면 이하의 일정한 심도 내로 주입하고, 주입 심도는 1~2nm인 것이 바람직하다. 이로써, ITO표면 및 표면 이하의 일정한 심도 내에서 대량의 H－O결합을 형성함으로써 ITO표면의 산소 빈자리 농도를 제고시키고 ITO표면의 일함수를 효과적으로 감소시킨다. 상기 방법에 의하면, 주입 심도는 ITO표면 이하의 일정한 심도 내이고 전체 ITO박막의 두께는 수백 나노미터이므로, ITO박막의 투명성과 전기 전도성에 영향을 미치지 않는다. 이 밖에, 상기 펄스용 부 바이어스의 크기를 조절함으로써 상기 플라즈마의 주입 심도를 제어하고, 상기 플라즈마의 강도를 조절함으로써 상기 플라즈마의 주입 농도를 제어한다.Referring to FIG. 4, the work function of ITO (In ₂ O ₃ / SnO ₂ ) and the oxygen vacancy concentration therein are closely related,

to be. That is, the higher the oxygen vacancy concentration, the smaller the value of the calculation formula and the smaller the work function. Therefore, it is preferable that ions generated by hydrogen atoms are implanted into the ITO surface and a certain depth below the surface by using the plasma immersion ion implantation method, and the depth of implantation is 1 to 2 nm. As a result, a large amount of H-O bonds are formed within the ITO surface and a certain depth below the surface, thereby increasing the oxygen vacancy concentration on the ITO surface and effectively reducing the work function of the ITO surface. According to the above method, the depth of implantation is within a certain depth below the ITO surface and the thickness of the entire ITO thin film is several hundred nanometers, so that the transparency and electrical conductivity of the ITO thin film are not affected. In addition, the injection depth of the plasma is controlled by adjusting the size of the pulse side bias, and the plasma injection density is controlled by controlling the intensity of the plasma.

Example 2

Referring to FIG. 4, a plasma (for example, Li, Mg, Cs, etc.) generated by a low work function metal atom is implanted into the ITO surface and a certain depth below the surface Inject. As a result, the electron concentration on the surface of the cathode can be increased, the Fermi energy level on the surface of the cathode can be improved, the work function of the ITO thin film can be reduced, and the electron injection efficiency can be effectively improved. Similarly, since these metal elements are injected only at a certain depth below the ITO surface, they do not affect the transparency and electrical conductivity of the ITO thin film. In addition, the injection depth of the plasma is controlled by adjusting the size of the pulse side bias, and the plasma injection density is controlled by controlling the intensity of the plasma.

The present invention, on the other hand, improves the oxygen vacancy concentration on the ITO surface and effectively reduces the work function of ITO by forming a large amount of H-O bonds in the ITO thin film by injecting a plasma generated by the hydrogen atom in the ITO thin film . In addition, if a plasma generated by a hydrogen atom is injected only into the ITO surface, it is easily released, so that the plasma generated by the hydrogen atom is injected into the ITO surface and a certain depth below the surface. Since the plasma can be confined in the ITO surface, it is more difficult to separate the plasma than when it is injected only on the surface, so that higher stability can be realized and the function of improving the oxygen vacancy can not easily be lost. On the other hand, by injecting a plasma generated by a metal atom having a low work function in the ITO thin film, the work function of ITO can be reduced and the electron concentration on the surface of the cathode can be improved, . In addition, when a plasma generated by a metal atom having a low work function is injected into the entire ITO, the transparency of the entire ITO thin film is deteriorated. Therefore, by injecting the plasma generated by the metal atom having a low work function into the ITO surface and a certain depth below the surface, the electrical conductivity of the ITO thin film can be increased, and the transparency of the ITO thin film is not affected.

Therefore, the method of manufacturing the reverse structure OLED according to the present invention can obtain a low work function ITO cathode and maintain transparency and electrical conductivity of the ITO thin film. In addition, when the OLED part is manufactured using the ITO treated by the method of the present invention as a cathode, it is possible to effectively improve the outgoing light efficiency and the stability of the parts.

The foregoing is merely a preferred embodiment of the present invention, and the present invention is not limited to any formal limitations. While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims. All such modifications, changes and equivalents will be included within the scope of the present invention.

10: substrate
20: ITO thin film
30: electron injection layer
40: electron transport layer
50: light emitting layer
60: hole transport layer
70: anode
91: substrate
92: Bipolar ITO
93: hole transport layer
94: light emitting layer
95: electron transport layer
96: electron injection layer
97: cathode
98: cathode ITO
99: anode

Claims (5)

Providing a substrate, and fabricating an ITO thin film on the substrate to form a cathode;
Performing plasma immersion ion implantation on the ITO thin film and applying a pulse negative bias to the ITO thin film to inject the plasma into the ITO thin film according to a set depth of implantation;
Forming an organic layer including an electron injecting layer, an electron transporting layer, a light emitting layer, and a hole transporting layer through film forming in order on the ITO thin film; And
And forming an anode through film forming in the organic layer. ≪ RTI ID = 0.0 > 11. < / RTI > The method according to claim 1,
Wherein the injection depth of the plasma is controlled by controlling the size of the pulse side bias, and the injection concentration of the plasma is controlled by controlling the intensity of the plasma. The method according to claim 1,
Wherein the depth of implantation of the plasma is 1 to 2 nm. 4. The method according to any one of claims 1 to 3,
Wherein the plasma is generated by a hydrogen atom or by a metal atom of a low work function. 5. The method of claim 4,
Wherein the metal atom of the low work function is a lithium atom, a magnesium atom, or a cesium atom.

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