JP2005019407A - Organic el element and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic EL element and a manufacturing method for it improved in the stability of a transparent negative electrode conductive layer. <P>SOLUTION: This organic EL element is formed with a positive electrode layer, an organic functional layer, and a co-evaporation layer at least. The organic functional layer is positioned on the positive electrode layer, while the co-evaporation layer is positioned on the organic functional layer. The co-evaporation layer is provided with a metal layer and an MTiO<SB>3</SB>layer (M represents a metal layer material), and the metal layer serves as a principal negative electrode layer. The MTiO<SB>3</SB>layer is formed by co-evaporation between a low work function metal and a metal oxide. In this way, adhesion between the negative electrode metal and the co-evaporation layer is improved, and the conductivity and protection of the negative electrode can be reinforced, while a light output amount of the organic EL element is increased by a high refraction index. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an organic EL (OEL) element and a method for manufacturing the same, and more particularly to a cathode conductive layer capable of improving the stability of the organic EL element and a technique for increasing the light outcoupling of the organic EL element.

  Organic EL devices have features such as self-emission, wide viewing angle, high response speed, low drive voltage, full color, and are already in practical use, such as small display panels, outdoor screens, personal computers and TV screens. It can be applied to various color flat display elements. The organic EL element has a configuration in which an organic layer having light emission characteristics is sandwiched between two electrodes. When a DC voltage is applied to the two electrodes, holes are injected from the anode and electrons are injected from the cathode. The electric field generated by the applied voltage causes the carriers to move into the organic light emitting layer and cause carrier recombination. Part of the energy released by recombination of electrons and holes excites the luminescent molecules. When the excited luminescent molecule releases energy and returns to the ground state, a certain ratio of energy is released in the form of photons. This is the light emission principle of the organic EL element. A generally known organic EL element is as shown in FIG.

FIG. 1 is a schematic cross-sectional view of a well-known organic EL element. As shown in FIG. 1, the organic EL element 100 includes a substrate 10 formed of glass or the like, a cathode layer 18, an anode layer 12 formed of transparent indium tin oxide (ITO) or the like, and a cathode layer 18. An organic functional layer (EML) 16 having light emission characteristics formed between the anode layers 12 is provided.
The cathode 18 of the organic EL element 100 is usually formed of a low work function active metal such as calcium, magnesium, or a magnesium silver alloy, or a transparent metal oxide such as indium tin oxide or indium zinc oxide (IZO). Since the value of the refractive index n of the organic functional layer 16 is about 1.7, a cap layer 22 having a higher refractive index n is deposited above the cathode 18 to reduce the total reflection phenomenon at the interface, thereby reducing the light extraction amount. Need to be increased.

In order to obtain the cathode 18 having relatively high stability, the organic EL element often employs a transparent electrode of indium tin oxide, which must be formed by sputter deposition. There is a problem that the EL element 100 is easily damaged.
Accordingly, one object of the present invention is to provide an organic EL device with improved stability of the transparent cathode conductive layer and a method for producing the same.
Another object of the present invention is to provide an organic EL device that increases the light extraction amount and improves the stability of the transparent cathode conductive layer, and a method for manufacturing the same.

Based on the above and other objects, the organic EL device provided by the present invention includes at least an anode layer, an organic functional layer, and a co-evaporated cathode layer. The organic functional layer is located on the anode layer, and the co-deposited cathode layer is located on the organic functional layer. The co-evaporated cathode layer includes a metal layer and an MTiO ₃ layer (where M in MTiO ₃ represents the material of the metal layer). The MTiO ₃ layer can be formed of a conductive material which is a high refractive index transparent metal oxide produced by co-evaporation of a low work function metal and titanium oxide. The metal layer can be formed of a metal material having a low work function, and for example, an element of Group 2A of the periodic table can be adopted.
The metal titanium oxide formed by co-evaporation functions as a cathode layer of the organic EL element due to its conductivity, and can also function as a cap layer due to its transparent and high refractive index characteristics.
The present invention also provides a novel and useful method for producing an organic EL device. In this manufacturing method, a substrate is first prepared, then an anode layer is formed on the substrate, an organic functional layer is vapor-deposited on the anode layer, and then a co-evaporated layer is formed on the organic functional layer.

As described in a preferred embodiment of the present invention, which will be described later, the co-deposited layer is formed by first depositing a metal layer on the organic functional layer using a co-evaporation method, and then co-depositing with titanium oxide to form the MTiO ₃ layer. Form.

  In the present invention, the transparent conductive layer formed by the co-evaporation method is used as the cathode layer, so that the cathode layer has a high refractive index n and reduces the phenomenon that the light emitted from the organic functional layer is totally reflected at the interface. can do. The amount of light absorbed by the organic layer can be reduced, and the amount of light extracted increases. In addition, the adhesion to the cathode metal layer is good and the cathode metal layer is protected.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments for carrying out the present invention will be described in detail with reference to the drawings. FIG. 2 is a flowchart showing a manufacturing procedure of the organic EL (OEL) element of this embodiment. FIG. 3 is a schematic cross-sectional view of the organic EL element 300 manufactured by the flowchart shown in FIG.

Please refer to FIG. First, in step 200, the substrate 30 is prepared. The material of the substrate 30 may be, for example, glass, or other substrate material suitable for use.
In step 202, an anode layer 302 is formed on the substrate 30. As the material of the anode layer 302, for example, indium tin oxide (ITO) can be adopted, or other metals suitable for use can be adopted.

In step 204, an organic functional layer 306 is formed on the anode layer 302. In the step of forming the organic functional layer 306 on the anode layer 302, a hole transport layer (HTL) 304 is first formed on the anode layer 302 so that the transport of holes from the anode layer 302 is promoted. Next, an organic light emitting layer 310 is formed on the hole transport layer 304, and an electron transport layer (ETL) 314 is formed on the organic light emitting layer 310 so as to facilitate the transport of electrons from the cathode.
Further, before forming the hole transport layer 304 on the anode layer 302, a hole injection layer (HIL) (not shown) may be further formed on the anode layer 302. Accordingly, holes can be injected into the organic light emitting layer 310 even when the applied voltage is low. In addition, after the electron transport layer 314 is formed on the organic light emitting layer 310, an electron injection layer (EIL) may be further formed on the electron transport layer 314 (not shown). Thereby, the injection of electrons from the cathode can be promoted.

In step 206, a co-evaporation layer 312 is formed on the electron transport layer 314 by co-evaporation. In this co-evaporation step, a thin metal layer 313a is first formed by vapor deposition on the electron transport layer 314, and then the metal and titanium oxide (TiO) are co-evaporated to deposit a metal oxide on the metal layer 313a. To do. Thereby, the MTiO ₃ layer 313b having good interface bonding with the metal layer 313a can be formed. Here, M in MTiO ₃ represents a metal material forming the metal layer 313a. The metal layer 313a and the MTiO ₃ layer 313b constitute a co-evaporation layer 312 that is transparent and has conductivity. In this simultaneous vapor deposition step, the chamber pressure may be controlled within the range of 10 ⁻⁴ to 10 ⁻⁵ Torr. Each of the above-described layers such as the hole transport layer 304, the organic light emitting layer 310, the hole injection layer, the electron transport layer 314, and the electron injection layer can be formed by thermal evaporation. The simultaneous vapor deposition process has good compatibility with the manufacturing process of other layers, and for example, it is possible to share the same vapor deposition apparatus. The cathode layer of the organic EL element can be formed without using a sputter deposition method that easily damages the organic EL element.

  FIG. 3 is a schematic cross-sectional view of an organic EL device according to a preferred embodiment of the present invention. Please refer to FIG. The organic EL element 300 of the present embodiment includes a substrate 30, an anode layer 302, an organic functional layer 306, a co-evaporation layer 312 and the like. As for the arrangement of each layer in the organic EL element 300, the anode 302 is located on the substrate 30, the organic functional layer 306 is located on the anode layer 302, and the co-evaporated layer 312 is located on the organic functional layer 306. Among these, the organic functional layer 306 includes at least the organic light emitting layer 310, and a hole transport layer 304 may be further disposed between the organic light emitting layer 310 and the anode layer 302. An electron transport layer 314 may be further disposed between the layer 312 and the layer 312. In the organic functional layer 306, a hole injection layer (not shown) can be further disposed between the anode layer 302 and the hole transport layer 304. Thereby, holes can be moved to the organic light emitting layer 310 even when the applied voltage is low. In addition, an electron injection layer (not shown) may be further disposed between the electron transport layer 314 and the co-evaporation layer 312 in the organic functional layer 306. Thereby, electrons are more easily moved to the organic light emitting layer 310.

Still referring to FIG. The co-evaporation layer 312 of this embodiment is a layer formed by a co-evaporation method, and includes a metal layer 313a and an MTiO ₃ layer 313b. The co-evaporated layer 312 is a transparent conductive layer having a high refractive index n. For example, the value of the refractive index n is greater than about 1.7. In the co-evaporated layer 312, the metal layer 313a mainly functions as a cathode. In addition, the MTiO ₃ layer 313b serves as a supplementary cathode and also serves as a cap layer. M in the MTiO ₃ layer 313b represents a metal element and can be made of the same material as that of the metal layer 313a. For example, the metal layer 313a is preferably a metal having a low work function such as calcium, barium, strontium, magnesium, etc., and elements of group 2A of the periodic table can be mainly used. By performing simultaneous vapor deposition using the same material as the metal layer 313a, the material of the MTiO ₃ layer 313b is calcium titanate CaTiO ₃ , barium titanate BaTiO ₃ , strontium titanate SrTiO ₃ , magnesium titanate MgTiO _3, etc. Can be adopted. For example, the MTiO ₃ layer 313b such as calcium titanate or magnesium titanate has a refractive index n of about 2.3 to 2.4, which is advantageous for reducing the total reflection at the interface, and can increase the light extraction amount. it can. In this embodiment, although the case where the material of the metal layer 313a is calcium is taken as an example, the interface bond between calcium and calcium titanate is good, the adhesiveness is high, and the calcium titanate is a metal layer of calcium. There exists an effect which protects 313a. In addition, since MTiO ₃ has conductive characteristics, the driving voltage of the organic EL element 300 can be reduced.

  The feature of the organic EL element of this embodiment is that a transparent conductive layer is formed by a co-evaporation method. Since this transparent conductive layer has a high refractive index (n) characteristic, it also functions as a cap layer for the organic EL element. Since this transparent conductive layer has conductivity, it functions as an auxiliary electrode for a cathode made of a metal having a low work function. Since this transparent conductive layer is a stable transparent metal oxide, it functions to protect the organic EL element and particularly its cathode from erosion of water and oxygen.

Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.
The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology illustrated in the present specification or the drawings achieves a plurality of objects at the same time, and has technical utility by achieving one of the objects.

1 is a schematic cross-sectional view of a generally known organic EL element. It is a flowchart which shows the manufacture procedure of the organic EL element of embodiment. It is a section schematic diagram of an organic EL element of an embodiment.

Explanation of symbols

10, 30... Substrate 12, 302.. Anode layer 310. Organic light emitting layer 18 cathode layer 22 cap layer 100 publicly known organic EL element 300 .. organic EL element 304 of the embodiment - a hole transport layer 16,306 ... organic functional layers 312 ... codeposition layer 313a ... metal layer 313b ... MTiO ₃ layers 314 ... electron transport layer

Claims (28)

An anode layer;
An organic functional layer located on the anode layer;
A co-deposited cathode layer located on the organic functional layer and comprising an MTiO ₃ layer;
At least,
The organic EL element, wherein M is selected from metal elements. 2. The organic EL device according to claim 1, wherein the co-evaporated cathode layer includes a metal layer of the same kind as M of the MTiO ₃ layer.   The organic EL device according to claim 2, wherein the metal layer includes an element of Group 2A of the periodic table.   The organic EL element according to claim 3, wherein the metal layer contains at least one of calcium, magnesium, barium, and strontium. The MTiO _{3 layers, CaTiO 3, BaTiO 3, SrTiO} 3, the organic EL device according to claim 1, characterized in that it comprises at least one of MgTiO _3.   2. The organic EL device according to claim 1, wherein the value of the refractive index n of the co-evaporated cathode layer is larger than 1.7.   The organic EL element according to claim 1, wherein the organic functional layer includes at least an organic light emitting layer. The organic functional layer is
An electron transport layer located between the organic light emitting layer and the co-deposited cathode layer;
A hole transport layer located between the organic light emitting layer and the anode layer;
The organic EL device according to claim 7, further comprising:   The organic EL device according to claim 8, wherein the organic functional layer further includes an electron injection layer positioned between the co-evaporated cathode layer and the electron transport layer.   9. The organic EL device according to claim 8, wherein the organic functional layer further includes a hole injection layer located between the hole transport layer and the anode layer. A method for manufacturing an organic EL element,
Preparing a substrate;
Forming an anode layer on the substrate;
Forming an organic functional layer on the anode layer;
Forming a co-deposited cathode layer on the organic functional layer using a co-evaporation method;
The manufacturing method of an organic EL element provided with. Forming the co-deposited cathode layer comprises:
Depositing a metal layer on the organic functional layer;
Performing co-evaporation of the metal layer with metal and titanium oxide to form an MTiO ₃ layer;
The manufacturing method of the organic EL element of Claim 11 characterized by the above-mentioned. 13. The method of manufacturing an organic EL element according to claim 12, wherein M of the MTiO ₃ layer is the same kind of metal as the metal layer.   The method for producing an organic EL element according to claim 12, wherein the metal layer contains an element of Group 2A of the periodic table.   The method for producing an organic EL element according to claim 14, wherein the metal layer contains at least one of calcium, magnesium, barium, and strontium. The MTiO _{3 layers, CaTiO 3, BaTiO 3, SrTiO} 3, the method of manufacturing the organic EL device according to claim 12, characterized in that it comprises at least one of MgTiO _3.   The method for producing an organic EL element according to claim 11, wherein the value of the refractive index n of the co-evaporated cathode layer is larger than 1.7.   12. The method of manufacturing an organic EL element according to claim 11, wherein the step of forming the organic functional layer includes a step of forming an organic light emitting layer on the anode layer. Forming the organic functional layer comprises:
Forming a hole transport layer on the anode layer performed before the step of forming the organic light emitting layer;
Forming an electron transport layer on the organic light emitting layer, which is performed after the step of forming the organic light emitting layer, and
The method of manufacturing an organic EL element according to claim 18, further comprising:   The method of manufacturing an organic EL element according to claim 19, further comprising a step of forming a hole injection layer on the anode layer, which is performed before the step of forming the hole transport layer.   The method for manufacturing an organic EL element according to claim 19, further comprising a step of forming an electron injection layer on the electron transport layer, which is performed after the step of forming the electron transport layer. A cathode structure suitable for being disposed in an organic EL element, comprising a MTiO ₃ layer, wherein M is selected from metal elements.   The cathode structure according to claim 22, further comprising a metal layer.   24. The cathode structure according to claim 23, wherein the metal layer includes an element of Group 2A of the periodic table.   The cathode structure according to claim 24, wherein the metal layer includes at least one of calcium, magnesium, barium, and strontium. The cathode structure according to claim 23, wherein M of the MTiO ₃ layer is the same kind of metal as the metal layer. Cathode structure according to claim 23 wherein the MTiO _{3 layers,} characterized in that it comprises at least one _{CaTiO 3, BaTiO 3, SrTiO 3} , MgTiO 3.   24. The cathode structure according to claim 23, wherein the value of the refractive index n of the cathode structure is greater than 1.7.

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