KR101450858B1 - Organic electroluminescent device and fabracation method by using graphene oxide - Google Patents

Abstract

The present invention relates to an organic electroluminescent device using graphene oxide and a method of manufacturing the same, wherein an anode, a hole injecting layer, a light emitting layer, an electron injecting layer and a cathode are stacked on a substrate, Or an electron injecting layer comprises graphene oxide, and a method of manufacturing the same.

Description

TECHNICAL FIELD [0001] The present invention relates to an organic electroluminescent device using graphene oxide and a method of manufacturing the same. BACKGROUND ART < RTI ID = 0.0 >

The present invention relates to an organic electroluminescent device using graphene oxide and a method of manufacturing the same, and more particularly, to an organic electroluminescent device using graphene oxide as a hole injecting layer and an electron injecting layer To an electroluminescent device and a manufacturing method thereof.

Generally, an electroluminescent device using an electroluminescence phenomenon that emits light when an electric field is applied to a substance that emits strong fluorescence is classified into an inorganic electroluminescent device using inorganic phosphors such as ZnS and Mn as a luminescent center There is an organic electroluminescent element in which a light emitting element, an organic material, and an organic material are dispersed in a polymer matrix.

FIG. 1 shows the structure of an organic electroluminescent device. Referring to FIG. 1, the organic electroluminescent device has a thin film multilayer structure having a thickness of several tens of nanometers (nm).

A transparent electrode 105 is disposed on the substrate 106 and the holes 108 injected from the transparent electrode 105 are injected into the hole injection layer 104 In the light-emitting layer 103, an exciton is formed by the electrons injected from the cathode 101 and passed through the electron injection layer 102, and emitted (107) through recombination 110 .

In the case of the organic electroluminescent device, a light emitting polymer is supplied with holes and electrons between an anode and a cathode to emit light to the outside by recombination of holes and electrons , The performance of the device can be improved only by smoothly injecting or moving holes and electrons from both electrodes. Further, in the case of an organic electroluminescent device, since it is made of a thin film of several tens of nanometers, a cross talk phenomenon occurs between the anode and the cathode, causing leakage of current, have.

Therefore, a functional layer for reducing crosstalk and increasing the injection efficiency of holes and electrons by using a material having a sufficiently large bandgap between the electrode and the light emitting polymer, that is, a material having a high resistance, (transport layer) and an electron injection (transport layer).

In general, the hole injection layer mainly used in the conventional organic electroluminescent device includes PEDOT: PSS (poly (3,4-ethylenedioxythiophere poly (styrene sulfonate), PVK (poly (9-vinylcarbazole) N'-diphenyl-N, N'-bis (1-naphthyl) ethyl] ) -1,1'biphenyl-4,4'-diamine, TPD (N, N'-Bis- (3-methylphenyl) -N, N'- 4'-diamine), etc. However, the conductive organic materials are vulnerable to oxidation and moisture, have a short lifetime, and have limited hole mobility.

In the case of the electron injection layer, a thin film of about 1 nm or less made of LiF, CsF, NaF, Cs ₂ CO ₃ , or the like may be deposited or a deposited layer of about 20 nm or less made of Ca, Li, Ba, Cs, Which is very vulnerable to oxygen and moisture in the outside air during the additional deposition process of the cathode, and there is a problem that handling of materials and devices is not easy due to the weakness of oxidation even after the final process.

In order to solve the above problems, the present invention provides a conventional hole injecting layer which is vulnerable to oxygen and moisture, an organic electroluminescent device replacing the electron injecting layer with graphene oxide, and a method of manufacturing the same.

In one or more embodiments of the present invention, an anode, a hole injecting layer, a light emitting layer, an electron injecting layer, and a cathode are stacked on a substrate, wherein at least one of the hole injecting layer or the electron injecting layer is graphene An organic electroluminescent device, and an organic electroluminescent device.

The hole injection layer chloride rhodium (RhCl _3), palladium chloride (PdCl _2), chloride, gold (Ⅲ) (AuCl _3), chloride, molybdenum (MoCl _3), iridium chloride (IrCl _3), chloride, osmium (OsCl ₃₎ of the Doping a material comprising at least one material into the graphene oxide.

The electron injection layer contains at least one of an alkali metal such as cesium carbonate (Cs ₂ CO ₃ ), rubidium carbonate (Rb ₂ CO ₃ ), calcium carbonate (K ₂ CO ₃ ), lithium carbonate (Li ₂ CO ₃ ) Doped into a graphene oxide. ≪ RTI ID = 0.0 > [0035] < / RTI >

The graphene oxide may comprise at least one of a surfactant, a polar solvent or a non-polar solvent.

In one or more embodiments of the present invention, in the method of manufacturing an organic electroluminescent device in which an anode, a hole injection layer, a light emitting layer, an electron injection layer, and a cathode are laminated on a substrate, step; Dispersing the graphene oxide in a dispersion solution to prepare a graphene oxide solution for coating the hole injection layer or the electron injection layer; Forming a hole injection layer by coating a graphene oxide solution prepared for coating the hole injection layer on the anode; Coating a polymer light emitting layer on the hole injection layer; Forming an electron injection layer by coating a graphene oxide solution prepared for coating the electron injection layer on the light emitting layer; And a step of depositing a cathode on the electron injection layer.

The dispersion solution is characterized by being at least one of a surfactant, a polar solvent and a non-polar solvent.

The step of preparing the graphene oxide solution for coating the hole injection layer may include the steps of preparing rhodium chloride (RhCl ₃ ), palladium chloride (PdCl ₂ ), chloride (AuCl ₃ ), molybdenum chloride (MoCl ₃ ) (P-doping) a material containing at least one of iridium (IrCl ₃ ) and osmium chloride (OsCl ₃ ) to graphene oxide.

The step of preparing the graphene oxide solution for coating the electron injecting layer may include the steps of preparing cesium carbonate (Cs ₂ CO ₃ ), rubidium carbonate (Rb ₂ CO ₃ ), calcium carbonate (K ₂ CO ₃ ), lithium carbonate ₂ CO ₃ ), or the like, to the graphene oxide.

After the step of producing graphene, the step of extracting graphene oxide using centrifugation may further be included.

The valence band of the hole injection layer is located between a work-function of the anode and a highest occupied molecular orbital of the emission layer, and a conduction band of the hole injection layer ) Has a work function lower than a lowest unoccupied molecular orbital of the light emitting layer (lowest unoccupied molecular orbital).

The conduction band of the electron injection layer is located between the lowest unoccupied molecular orbital of the light emitting layer and the work function of the cathode, and the valence band of the electron injection layer is located between the emissive layer And has a higher work function than the highest occupied molecular orbital.

According to the embodiments of the present invention, it is possible to stably exhibit the performance of the organic electroluminescent device and prolong the lifetime by forming the electron injection layer and the hole injection layer at low cost and stable in the atmosphere.

1 shows a structure of an organic electroluminescent device.
FIG. 2 shows the structure of an organic electroluminescent device in which a conventional hole injection layer material is replaced with graphene oxide.
FIG. 3 shows the structure of an organic electroluminescent device in which a conventional electron injection layer material is replaced by graphene oxide.
FIG. 4 shows the structure of an organic electroluminescent device in which a conventional hole injecting layer and an electron injecting layer material are replaced with graphene oxide.
FIG. 5 is a flowchart illustrating a manufacturing process of an organic electroluminescent device according to an embodiment of the present invention.
6 is an energy band diagram of an organic electroluminescent device.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention, and the manner of achieving them, will be apparent from and elucidated with reference to the embodiments described hereinafter in conjunction with the accompanying drawings. However, it is to be understood that the present invention is not limited to the disclosed embodiments, but may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. It is intended that the disclosure of the present invention be limited only by the terms of the appended claims. Like reference numerals refer to like elements throughout the specification.

In the embodiment of the present invention, a hole injection layer for injecting and transporting holes from the anode to the light emitting layer in the functional layers of the organic electroluminescent device, and an electron injecting layer for injecting and transporting electrons from the cathode to the light emitting layer A graphene oxide functional layer is disclosed.

In order to achieve the above object, according to the present invention, a graphene oxide which can be subjected to a solution process is synthesized and added as a functional layer of an organic electroluminescent device, so that a performance corresponding to a device using a conventional material can be exhibited do.

Hereinafter, a method for fabricating an organic electroluminescent device according to an embodiment of the present invention will be described.

FIG. 5 is a flowchart illustrating a manufacturing process of an organic electroluminescent device according to an embodiment of the present invention. Referring to FIG. 5, graphite oxide is prepared from graphite powder (S110). The graphene oxide is divided into various sizes ranging from nanometer (nm) to several millimeters (mm). In order to apply it to thin film devices such as organic solar cells and organic light emitting diodes, The pin oxide is extracted by centrifugation.

Then, the graphene oxide solution is prepared so that the extracted graphene oxide can be completely dispersed in a readily dispersible solution and used as a material for the hole injection layer 104 and the electron injection layer 102 (S120). The dispersion may be achieved by a graphene oxide, a surfactant, a polar solvent or a non-polar solvent.

The graphene oxide solution is used to form a thin film by coating a positive electrode 105 patterned on a glass substrate 106 to form a hole injection layer 104 (S130) Or a P-doped solution may be used. The P- doping is carried graphene as rhodium chloride that to further increase the work function of the oxide (RhCl _3), palladium chloride (PdCl _2), gold chloride (Ⅲ) (AuCl _3), molybdenum chloride (MoCl _3), A P-doped graphene oxide is produced by doping a material containing at least one of iridium chloride (IrCl ₃ ) and osmium chloride (OsCl ₃ ) into graphene oxide .

Then, the polymer light emitting layer 103 is coated on the hole injection layer 104 (S140). The coating of the polymer light-emitting layer 103 can be coated by a general method applied in the technical field to which the present invention pertains, so a detailed description thereof will be omitted here.

Then, an electron injection layer 102 is formed on the light emitting layer 103 (S150). The solution for forming the electron injection layer 102 is coated with a graphene oxide solution or an N-doped solution.

The N-doping includes any one of alkali metals such as cesium carbonate (Cs ₂ CO ₃ ), rubidium carbonate (Rb ₂ CO ₃ ), calcium carbonate (K ₂ CO ₃ ), lithium carbonate (Li ₂ CO ₃ ) Doped graphene oxide to further lower the work function by N-doping the material to be formed into graphene oxide.

After the electron injection layer 102 is formed as described above, the cathode 101 is deposited (S160) to fabricate an organic electroluminescent device.

FIG. 6 is an energy band diagram of an organic electroluminescent device according to an embodiment of the present invention. Referring to FIG. 6, in order for electrons and holes to recombine in the emission layer 103, The electrons injected from the cathode 101 must have a work function capable of injecting the electrons injected from the anode 105 into the light emitting layer 103 smoothly from the anode 105. At the same time, ) To prevent leakage of current.

In the case of the electron injection layer 102, the electrons 109 are injected smoothly and the holes 108 injected from the anode 105 do not form an exciton, It should block the coupling with the electron 109.

Therefore, in the embodiment of the present invention, the valence band of the hole injection layer 104 is determined by the work-function of the anode 105 and the highest occupied molecular orbital of the light-emitting layer 103 , HOMO) is good for the injection and transport of holes. The conduction band of the hole injection layer 104 has a work function lower than the lowest unoccupied molecular orbital (LUMO) of the light emitting layer 103, which is advantageous for blocking electrons.

The conduction band of the electron injection layer 102 is located between the work function of the cathode 101 and the lowest level non occupied molecular orbital (LUMO) of the light emitting layer 103, which is advantageous for electron injection and transportation, The valence band of the electron injection layer 102 has a work function higher than the highest level occupied molecular orbital (HOMO) of the light emitting layer 103, which is advantageous for blocking holes.

The above-mentioned graphene oxide satisfies the above-mentioned conditions, and the characteristics of the hole injection layer and the electron injection layer in the organic electroluminescent device are also possessed by graphene oxide. In the case of graphene oxide, a large band gap As a semiconductor material, it has characteristics similar to the conventional hole injection layer and electron injection layer. In addition, according to the embodiment of the present invention, the work function of a desired size can be easily obtained through surface doping.

That is, in the embodiment according to the present invention, since graphene oxide bonds with oxygen, it is resistant to oxygen and moisture and is graphene-based material, and has a high mobility and a work function suitable for an organic electroluminescent device. In addition, it is possible to change the work function appropriately depending on the electrode material having various work functions and a light emitting material having various conduction and valence band by varying the work function through various surface doping.

Hereinafter, embodiments of the present invention will be described in more detail.

FIG. 2 illustrates a structure of a conventional organic electroluminescent device in which a conventional hole injecting layer material is replaced with graphene oxide. FIG. 3 illustrates an organic electroluminescent device in which a conventional electron injecting layer material is replaced by graphene oxide FIG. 4 illustrates a structure of an organic electroluminescent device in which a conventional hole injecting layer and an electron injecting layer material are replaced with graphene oxide.

Referring to FIGS. 2 and 3, the injection efficiency of holes and electrons is improved by using a graphene oxide thin film such as a hole injection layer 201 and an electron injection layer 301 using graphene oxide, A short circuit phenomenon can be prevented. In FIGS. 2 and 3, each of the hole injecting layer and the electron injecting layer is independently used. The formation of the hole injecting layer and the electron injecting layer using graphene oxide is shown in FIG. As shown in FIG. 4, when the graphene oxide thin film is used for both the hole injection layer and the electron injection layer, the efficiency can be expected to increase.

As described above, graphene oxide having a graphene-based two-dimensional structure has high mobility, high transparency, and excellent mechanical characteristics. Therefore, graphene oxide is used to improve the organic electroluminescence The device can be manufactured.

The organic electroluminescent device according to the embodiment of the present invention is a next-generation high-efficiency surface light source, has a large area, and has a small heat generation. Therefore, the organic electroluminescent device has a great potential to replace the existing lighting and display market. In addition, since most of the layers constituting the device can be subjected to a solution process, the cost of the process can be reduced.

This is because the graphene oxide can be processed by a solution and has a lower cost and oxidation resistance than conventional polymer materials, thereby maximizing the advantages of the organic electroluminescent device.

In other words, the embodiment of the present invention can replace the conventional polymer hole injection layer which is vulnerable to oxygen and moisture and the electron injection layer of alkali metal series by using oxygen and graphene oxide which is resistant to moisture, Thereby increasing the efficiency and lifetime of the device, and lowering the cost of the device by replacing the conventional expensive material.

  While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, You will understand.

It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. The scope of the present invention is defined by the appended claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be interpreted as being included in the scope of the present invention .

Claims (12)

delete An organic electroluminescent device in which a cathode, a hole injection layer, a light emitting layer, an electron injection layer, and a cathode are laminated on a substrate,
Wherein either the hole injection layer or the electron injection layer contains graphene oxide,
The hole injection layer chloride rhodium (RhCl _3), palladium chloride (PdCl _2), chloride, gold (Ⅲ) (AuCl _3), chloride, molybdenum (MoCl _3), iridium chloride (IrCl ₃₎ or chloride osmium (OsCl ₃₎ of the Doped with a material including at least one dopant, and doping the doped material with graphene oxide. An organic electroluminescent device in which a cathode, a hole injection layer, a light emitting layer, an electron injection layer, and a cathode are laminated on a substrate,
Wherein either the hole injection layer or the electron injection layer contains graphene oxide,
The electron injecting layer is made of a material containing at least one of cesium carbonate (Cs ₂ CO ₃ ), rubidium carbonate (Rb ₂ CO ₃ ), calcium carbonate (K ₂ CO ₃ ), or lithium carbonate (Li ₂ CO ₃ ) (N-doping) a pin oxide. The method according to claim 2 or 3,
Wherein the graphene oxide comprises at least one of a surfactant, a polar solvent, and a non-polar solvent. A method of manufacturing an organic electroluminescent device in which an anode, a hole injection layer, a light emitting layer, an electron injection layer, and a cathode are stacked on a substrate,
Producing graphene oxide from graphite;
Dispersing the graphene oxide in a dispersion solution to prepare a graphene oxide solution for coating the hole injection layer or the electron injection layer;
Forming a hole injection layer by coating a graphene oxide solution prepared for coating the hole injection layer on the anode;
Coating a polymer light emitting layer on the hole injection layer;
Forming an electron injection layer by coating a graphene oxide solution prepared for coating the electron injection layer on the light emitting layer; And
And depositing a cathode on the electron injection layer,
Wherein the step of preparing the graphene oxide solution for coating the hole injection layer comprises:
Chloride, rhodium including (RhCl _3), palladium chloride (PdCl _2), chloride, gold (Ⅲ) (AuCl _3), chloride, molybdenum (MoCl _3), any one or more of iridium chloride (IrCl ₃₎ or chloride osmium (OsCl ₃₎ (P-doping) a material to be formed on the substrate to a graphene oxide. 6. The method of claim 5,
Wherein the dispersion solution is at least one of a surfactant, a polar solvent, and a non-polar solvent. delete delete The method according to claim 5 or 6,
Further comprising, after the step of preparing the graphene oxide, extracting the graphene oxide using centrifugation. The method according to claim 5 or 6,
The valence band of the hole injection layer is located between a work-function of the anode and a highest occupied molecular orbital of the emission layer, and a conduction band of the hole injection layer ) Has a work function lower than a lowest unoccupied molecular orbital of the light emitting layer. The method according to claim 5 or 6,
The conduction band of the electron injection layer is located between the work function of the cathode and the lowest unoccupied molecular orbital of the light emitting layer and the valence band of the electron injection layer is located between the light emitting layer Wherein the organic compound has a work function higher than a highest occupied molecular orbital of the organic light emitting device. A method of manufacturing an organic electroluminescent device in which an anode, a hole injection layer, a light emitting layer, an electron injection layer, and a cathode are stacked on a substrate,
Producing graphene oxide from graphite;
Dispersing the graphene oxide in a dispersion solution to prepare a graphene oxide solution for coating the hole injection layer or the electron injection layer;
Forming a hole injection layer by coating a graphene oxide solution prepared for coating the hole injection layer on the anode;
Coating a polymer light emitting layer on the hole injection layer;
Forming an electron injection layer by coating a graphene oxide solution prepared for coating the electron injection layer on the light emitting layer; And
And depositing a cathode on the electron injection layer,
Wherein the step of preparing the graphene oxide solution for coating the electron injection layer comprises:
A material containing at least one of cesium carbonate (Cs ₂ CO ₃ ), rubidium carbonate (Rb ₂ CO ₃ ), calcium carbonate (K ₂ CO ₃ ), or lithium carbonate (Li ₂ CO ₃ ) (N-doping) the organic electroluminescent device.

Images