KR20200142390A - Inorganic electroluminescent device comprising luminescent particle surrounded by a coating layer and method for producing same - Google Patents

Abstract

Disclosed are an inorganic electroluminescent device including a luminescent particle surrounded by a coating layer and a method for producing the same. The inorganic electroluminescent device comprises: an anode; an emission layer formed at an upper portion of the anode, and including a luminescent particle of an inorganic compound represented by chemical formula 1 and a coating layer coating a surface of the luminescent particle; and a cathode formed at an upper portion of the emission layer. At least a part of the coating layer adjacent to the anode in the coating layer includes an inorganic compound of chemical formula 2, and at least a part of the coating layer adjacent to the anode in the coating layer includes an inorganic compound of chemical formula 3. The chemical formula 1 is M^1A, the chemical formula 2 is (M^2)_(1+x)A, and the chemical formula 3 is (M^2)_(2-x)A. In the chemical formulas 1 to 3, the M^1 is second or twelfth group element, the A is two or more elements selected from the group consisting of chalcogen elements, the M^2 is a metallic element, and the x is represented as 0 <= x < 0.5. In the inorganic electroluminescent device, a specific inorganic compound is formed on a coating layer surrounding the luminescent particle so that DC driving is possible, the device may be driven at a low voltage, and emission efficiency may be improved.

Description

Inorganic electroluminescent device comprising luminescent particles surrounded by a coating layer and method for producing same}

It relates to an inorganic electroluminescent device including light-emitting particles surrounded by a coating layer and a method of manufacturing the same.

The phosphor material is a material that emits light when energy such as light, electricity, pressure, heat, or electron beam from outside is applied, and is a material known for a long time. Among these materials, phosphor materials made of inorganic materials are used in picture tubes, fluorescent lamps, electroluminescent (EL) devices, etc. from their luminous properties and stability. Recently, studies on inorganic phosphors have been actively conducted for use as color conversion materials in LEDs and for excitation by low-speed electron beams as in the case of PDPs.

Electroluminescent (EL) devices using powder particles in which individual particles act as individual luminescent sources have the advantage of preserving device properties during bending or stretching deformation. These properties of powder-based EL devices are promising in the field of lighting technology for next-generation devices such as artificial skin for humanoids and deformable light emitting devices. In addition, printing technology may be applied to the manufacturing process, and recently, UV-curable pastes capable of providing a device manufacturing process at room temperature have been developed, and thus, may have cost competitiveness compared to OLEDs based on thin films.

Electroluminescent (EL) devices using inorganic phosphor materials are largely classified as AC drive or DC drive according to their driving methods. The AC drive EL devices are divided into two types: a dispersion type in which phosphor particles are dispersed in a highly dielectric binder, and a thin film type in which a thin film of phosphor is sandwiched between two dielectric layers. As DC drive EL devices, DC thin film EL devices each having a thin film of phosphor sandwiched between a transparent electrode and a metal electrode and driven by low voltage direct current are included.

In particular, powder-based EL devices are not widely used because they are driven by alternating current (AC) of a high driving voltage. Therefore, it is relatively inefficient compared to a direct current (DC) drive device. Recently, various approaches such as optimizing the structure of an AC driven EL device have been used to overcome the disadvantages of low luminous efficiency and high driving voltage. As a representative approach, a dielectric material is introduced into the device to maximize the discharge effect, and it has recently been reported that the luminance of light emission can be improved by applying a retroreflective electrode.

Nevertheless, the performance of the EL element is still insufficient in practical use. From a fundamental point of view, this is because the AC driving EL device has limitations in achieving low voltage driving and efficiency comparable to DC driving devices such as light emitting diodes (LEDs) and OLEDs.

Research on DC-driven inorganic EL devices was actively conducted in the 1970s and 1980s (Journal of Applied Physics, 52(9), 5797, 1981). This kind of EL device is formed on a GaAs substrate using MBE. It is a device structured to have a film of ZnSe:Mn sandwiched between the substrate and the Au electrode. The light-emitting mechanism of such a device consists in that when a voltage of about 4 V is applied to the device, electrons are injected from the electrode by the tunnel effect and excite Mn as the light-emitting center. However, these devices have low luminous efficiency (~ 005 lm/W) and low reproducibility, and since then, commercialization or even academic research has not been conducted.

For example, the new direct current-driven inorganic EL device reported in WO 07/043676 uses a ZnS system containing luminescent centers known so far such as Cu or Mn as its luminous material, and the ZnS system is a transparent electrode, an ITO electrode and a rear surface. It has a structure sandwiched between Ag electrodes, which are electrodes. Although this document does not describe the light emitting mechanism of the device, it will be understood that Cu and Cl contained together in the system form a DA pair, and electrons and holes injected through the pair are recombined and emit light.

In addition, in JP-A-2006-233147, copper is contained as an activator, and at least any one of chlorine or bromine is contained as a study activator, and groups 6 to 6 of the second transition series or the third transition series An electroluminescent device using an inorganic phosphor composed of zinc sulfide particles containing at least one metal element belonging to Group 10 is disclosed.

Further, with the intention of adopting direct current driving, WO 07/139032 discloses a surface-emitting electroluminescent device in which a transparent metal oxide semiconductor/insulator is introduced.

Compared with organic EL devices that emit light by a driving method similar to the above, direct-current drive inorganic EL devices in which all components are inorganic materials have high durability and allow sufficient use in various fields such as lighting and displays. LEDs that are driven identically have similarities in that each and every component are inorganic materials, but the light emission from the LEDs is very small area, or equivalently, point light emission. Thus, even though LEDs produce lasers of high intensity per unit area, the generated lasers have a small absolute amount of light (luminous flux); As a result, LEDs have limited use. On the other hand, since inorganic EL devices are originally surface-emitting, inorganic EL devices have an advantage in terms of the possibility of obtaining a large number of light fluxes.

International Publication WO 07/043676 Japanese Published Patent Publication JP-A-2006-233147 International Publication WO 07/139032

An object of the present invention is to provide an inorganic electroluminescent device including a light emitting powder surrounded by a coating layer to enable direct current driving.

In order to achieve the above object, in one aspect of the present invention

Anode electrode;

A light-emitting layer formed on the anode electrode and including light-emitting particles, which are inorganic compounds represented by the following Formula 1, and a coating layer coated on the surface of the light-emitting particles; And

Includes; a cathode electrode formed on the emission layer,

At least a portion of the coating layer adjacent to the anode electrode of the coating layer contains an inorganic compound of the following formula (2),

At least a portion of the coating layer adjacent to the cathode electrode among the coating layers comprises an inorganic compound represented by the following formula (3):

<Formula 1>

M ¹ A

<Formula 2>

M ² _(1+x) A

<Formula 3>

M ² _(2-x) A

(In the formulas 1 to 3,

M ¹ is a Group 2 or 12 element,

Wherein A is at least one element selected from the group consisting of chalcogen elements,

M ² is a metal element,

Where x is 0 ≤ x <0.5)

Is provided.

In another aspect of the present invention

Preparing light-emitting particles, which are inorganic compounds represented by the following Chemical Formula 1;

Forming a coating layer by coating the surface of the light emitting particles with a metal;

Manufacturing a light emitting device in which a light emitting layer including light emitting particles on which the coating layer is formed is positioned between an anode electrode and a cathode electrode;

Applying a voltage to the light emitting device to form an inorganic compound of the following formula (2) on at least a portion of the coating layer adjacent to the anode electrode of the coating layer,

Forming an inorganic compound represented by the following Formula 3 on at least a portion of the coating layer adjacent to the cathode electrode among the coating layers;

Inorganic electroluminescent device manufacturing method comprising:

<Formula 1>

M ¹ A

<Formula 2>

M ² _(1+X) A

<Formula 3>

M ² _(2-X) A

(In the formulas 1 to 3,

M ¹ is a Group 2 or 12 element,

Wherein A is at least one element selected from the group consisting of chalcogen elements,

M ² is a metal element,

Where x is 0 ≤ x <0.5)

Is provided.

According to the inorganic electroluminescent device provided in one aspect of the present invention, by forming a specific inorganic compound in the coating layer surrounding the light emitting particles, direct current driving is possible, driving at a lower voltage is possible, and luminous efficiency can be improved. It works.

1 is a schematic diagram showing a light emitting layer according to an embodiment of the present invention,
2 is a schematic diagram showing the structure of a light emitting device according to an embodiment of the present invention,
3 is a band diagram of a light emitting device according to an embodiment of the present invention,
4 is a schematic diagram showing the structure of a light emitting device according to an embodiment of the present invention,
5 shows a band diagram of a light emitting device according to an embodiment of the present invention,
6 shows a phase equilibrium according to the atomic ratio of copper sulfide for an embodiment of the present invention,
7 shows a band gap according to a stoichiometric change of copper sulfide for an embodiment of the present invention,
8 shows a band diagram in a balanced state in which no voltage is applied to the light emitting device according to an embodiment of the present invention,
9 is a view showing a change in a band diagram as a voltage is applied to a light emitting device according to an embodiment of the present invention.
10 is a graph measuring emission luminance according to a driving voltage for embodiments of the present invention,
11 is a diagram showing a threshold voltage according to a formed voltage for embodiments of the present invention,
12 is a graph showing light emission luminance according to a driving voltage for embodiments of the present invention,
13 shows a threshold voltage according to a formed voltage for embodiments of the present invention,
13 is a graph comparing emission luminance according to a driving voltage with or without a hole injection layer in the embodiments of the present invention.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by an expert skilled in the art to which the present invention belongs. In general, the nomenclature used in this specification is well known and commonly used in the art.

In one aspect of the present invention

Anode electrode;

A light-emitting layer formed on the anode electrode and including light-emitting particles, which are inorganic compounds represented by the following Formula 1, and a coating layer coated on the surface of the light-emitting particles; And

Includes; a cathode electrode formed on the emission layer,

At least a portion of the coating layer adjacent to the anode electrode of the coating layer contains an inorganic compound of the following formula (2),

At least a portion of the coating layer adjacent to the cathode electrode among the coating layers comprises an inorganic compound represented by the following formula (3):

<Formula 1>

M ¹ A

<Formula 2>

M ² _(1+x) A

<Formula 3>

M ² _(2-x) A

(In the formulas 1 to 3,

M ¹ is a Group 2 or 12 element,

Wherein A is at least one element selected from the group consisting of chalcogen elements,

M ² is a metal element,

Where x is 0 ≤ x <0.5)

Is provided.

Hereinafter, the inorganic electroluminescent device provided in one aspect of the present invention will be described in detail for each configuration.

First, the inorganic electroluminescent device provided in one aspect of the present invention includes an anode electrode and a cathode electrode.

The anode electrode and the cathode electrode need to make at least one of the two electrodes transparent in order to emit light to the outside.

One transparent electrode among the anode and cathode electrodes is a material thereof, and is ITO, ZnO, AZO, TiO ₂ , SnO ₂ , In ₂ O ₃ , ZnSnO ₃ , AgInO ₂ , Zn ₂ In ₂ O ₅ , Zn ₂ Ga ₂ Materials such as O ₄ may be used, but are not limited thereto, and a generally used transparent electrode may be used.

As the material of the other electrode among the anode and cathode electrodes, metals such as Al, Au, Cu, Ag, Ni, and Pt may be used. When the entire inorganic electroluminescent device is made transparent, the other one The electrode material may be a transparent electrode using a material such as ITO, ZnO, AZO, TiO ₂ , SnO ₂ , In ₂ O ₃ , ZnSnO ₃ , AgInO ₂ , Zn ₂ In ₂ O ₅ , Zn ₂ Ga ₂ O ₄ . In addition, in the case of a high-contrast device, an oxide such as Mo, Ta, or Ti may be deposited to use a black electrode as the other electrode.

In addition, the inorganic electroluminescent device provided in one aspect of the present invention is formed on the anode electrode and includes a light-emitting layer including light-emitting particles, which are inorganic compounds represented by Formula 1 below, and a coating layer coated on the surface of the light-emitting particles. .

The light emitting particles are inorganic compounds represented by the following formula (1).

<Formula 1>

M ¹ A

M ¹ is a Group 2 or 12 element, and A is at least one element selected from the group consisting of a chalcogen element.

The light emitting particles may be, for example, ZnS, ZnO, ZnSe, ZnTe, CdS, CdSe, CdTe, CaS, SrS, SrSe, or BaS, but is not limited thereto.

The average particle diameter of the light-emitting particles is not particularly limited, but preferably, the 50% average particle diameter on a volume basis may be 0.2 µm to 2.0 µm, more preferably 0.3 µm to 0.7 µm. When the average particle diameter of the light-emitting particles exceeds 2.0 µm, it may be difficult to reduce the thickness, and there is a problem that the driving voltage may be increased, and when the average particle diameter of the light-emitting particles is less than 0.3 µm, there is a problem that the luminance may be lowered. Here, the 50% average particle diameter according to the volume basis (hereinafter sometimes referred to as ``average particle diameter'') is the median diameter (D50) of the volume-based particle size distribution measured by the laser Doppler method, for example, Nanotrack UPA- It can be measured using EX250 (manufactured by Nikiso Corporation, brand name, laser Doppler method particle size distribution measuring device).

The light-emitting particles may include a light-emitting center forming element.

The emission center forming element may be one or more selected from the group consisting of transition metals and rare earth metal elements, for example, Mn, Mo, Tc, Ru, Rh, Pd, Ag, W, Re, Os, Ir , Pt, Au may be, but is not limited thereto. These metal elements may be included alone, or may be included in a combination of two or more.

The light emitting center forming element may form a light emitting center in the light emitting particles, and there is no particular limitation on this method. For example, elements may be incorporated in the form of metal salts during grain formation through firing, or if melting, sublimation or reaction is possible under firing conditions, elements may be incorporated in the form of compound crystals. In addition to the portions to be incorporated into the inorganic compound crystals of the compound 1, the metals are preferably removed by etching, cleaning, or the like, in the precipitated portion on the crystal surface and the adsorbed portion on the crystal surface. As the metal salt, any of compounds including oxides, sulfides, sulfates, oxalates, halides, nitrates and nitrides may be employed. Among these salts, oxides, sulfides and halides are more preferred. These salts may be used alone or as a combination of two or more thereof.

The amount of the light-emitting center forming element is preferably 1×10 ^-7 to 1×10 ^-1 mol, and more preferably 1×10 ^-5 to 1×10 ^-2 mol with respect to 1 mol of the inorganic compound of Formula 1.

In addition, in the coating layer coated on the surface of the light emitting particles, at least a portion of the coating layer adjacent to the anode electrode contains an inorganic compound of Formula 2, and at least a portion of the coating layer adjacent to the cathode electrode includes an inorganic compound of Formula 3 do.

<Formula 2>

M ² _(1+X) A

<Formula 3>

M ² _(2-X) A

M ² is a metal element, A is at least one element selected from the group consisting of a chalcogen element, and x is 0≦x<0.5.

The M ² may be, for example, copper (Cu), but is not limited thereto.

The inorganic compound of Formula 2 may be a p-type semiconductor, and the inorganic compound of Formula 3 may be an n-type semiconductor.

The inorganic compound of Formula 2 may transfer holes to the light-emitting particles, and the inorganic compound of Formula 3 may transfer electrons to the light-emitting particles. Accordingly, in the light emitting particle, holes and electrons may combine to emit light.

The minimum energy value of the conduction band (CBM) of the inorganic compound of Formula 2 may be greater than the minimum energy value of the conduction band of the light emitting particle.

When the minimum energy value of the conduction band of the inorganic compound of Formula 2 is greater than the value of the light emitting particle, an energy barrier may be formed between the inorganic compound of Formula 2 and the light emitting particle, and as a result, the The electrons transferred to the light-emitting particles by the inorganic compound of Formula 3 do not flow toward the anode electrode and may bind with holes in the light-emitting particles.

In addition, the thickness of the emission layer is not particularly limited, but may preferably be 10 nm to 100 μm. When the thickness of the light emitting layer exceeds 100 μm, there is a problem that the driving voltage may increase, and when the thickness of the emission layer is less than 10 nm, there is a problem that insulation breakdown may occur.

In addition, the inorganic electroluminescent device provided in one aspect of the present invention may further include a hole injection layer between the anode electrode and the emission layer.

The hole injection layer is, for example, PEDOT:PSS (poly(3,4-ethylenedioxythiophere poly(styrene sulfonate)), PVK (poly(N-vinylcarbazole)), TFB (poly(9,9-dioctylfluorenyl-2,7-diyl )-co-(4,4'(N-(4-secbutylphenyl))diphenylamine)), a-NPD(N,N'-diphenyl-N,N'-bis(1-naphthyl)-1,1'biphenyl -4,4'-diamine), or TPD(N,N'-Bis-(3-methylphenyl)-N,N'-Bis-phenyl(1,1'-biphenyl)-4,4'-diamine, etc. However, it is not limited thereto.

Since the hole injection layer is formed, holes can more easily flow from the anode to the light emitting particles.

In another aspect of the present invention

Preparing light-emitting particles, which are inorganic compounds represented by the following Chemical Formula 1;

Forming a coating layer by coating the surface of the light emitting particles with a metal;

Manufacturing a light emitting device in which a light emitting layer including light emitting particles on which the coating layer is formed is positioned between an anode electrode and a cathode electrode;

Applying a voltage to the light emitting device to form an inorganic compound of the following formula (2) on at least a portion of the coating layer adjacent to the anode electrode of the coating layer,

Forming an inorganic compound represented by the following Formula 3 on at least a portion of the coating layer adjacent to the cathode electrode among the coating layers;

Inorganic electroluminescent device manufacturing method comprising:

<Formula 1>

M ¹ A

<Formula 2>

M ² _(1+X) A

<Formula 3>

M ² _(2-X) A

(In the formulas 1 to 3,

M ¹ is a Group 2 or 12 element,

Wherein A is at least one element selected from the group consisting of chalcogen elements,

M ² is a metal element,

Where x is 0 ≤ x <0.5)

Is provided.

Hereinafter, a method of manufacturing an inorganic electroluminescent device provided in another aspect of the present invention will be described in detail for each step.

First, a method of manufacturing an inorganic electroluminescent device provided in another aspect of the present invention includes preparing light-emitting particles, which are inorganic compounds represented by the following formula (1).

<Formula 1>

M ¹ A

M ¹ is a Group 2 or 12 element, and A is at least one element selected from the group consisting of a chalcogen element.

The light emitting particles may be, for example, ZnS, ZnO, ZnSe, ZnTe, CdS, CdSe, CdTe, CaS, SrS, SrSe, or BaS, but is not limited thereto.

The average particle diameter of the light-emitting particles is not particularly limited, but preferably, the 50% average particle diameter on a volume basis may be 0.2 µm to 2.0 µm, more preferably 0.3 µm to 0.7 µm. When the average particle diameter of the light-emitting particles exceeds 2.0 µm, it may be difficult to reduce the thickness, and there is a problem that the driving voltage may be increased, and when the average particle diameter of the light-emitting particles is less than 0.3 µm, there is a problem that the luminance may be lowered. Here, the 50% average particle diameter according to the volume basis (hereinafter sometimes referred to as ``average particle diameter'') is the median diameter (D50) of the volume-based particle size distribution measured by the laser Doppler method, for example, Nanotrack UPA- It can be measured using EX250 (manufactured by Nikiso Corporation, brand name, laser Doppler method particle size distribution measuring device).

The light-emitting particles may include a light-emitting center forming element.

The emission center forming element may be one or more selected from the group consisting of transition metals and rare earth metal elements, for example, Mn, Mo, Tc, Ru, Rh, Pd, Ag, W, Re, Os, Ir , Pt, Au may be, but is not limited thereto. These metal elements may be included alone, or may be included in a combination of two or more.

The light emitting center forming element may form a light emitting center in the light emitting particles, and there is no particular limitation on this method. For example, elements may be incorporated in the form of metal salts during grain formation through firing, or if melting, sublimation or reaction is possible under firing conditions, elements may be incorporated in the form of compound crystals. In addition to the portions to be incorporated into the inorganic compound crystals of the compound 1, the metals are preferably removed by etching, cleaning, or the like, in the precipitated portion on the crystal surface and the adsorbed portion on the crystal surface. As the metal salt, any of compounds including oxides, sulfides, sulfates, oxalates, halides, nitrates and nitrides may be employed. Among these salts, oxides, sulfides and halides are more preferred. These salts may be used alone or as a combination of two or more thereof.

The amount of the light-emitting center forming element is preferably 1×10 ^-7 to 1×10 ^-1 mol, and more preferably 1×10 ^-5 to 1×10 ^-2 mol with respect to 1 mol of the inorganic compound of Formula 1.

The method of manufacturing the light-emitting particles is not particularly limited, for example, a complex thermal decomposition method in which an organic complex containing a predetermined metal is decomposed by heat to produce oxide-based light-emitting particles; Combustion synthesis method in which light-emitting particles are produced by using a high-temperature self-propagation reaction using a compound serving as a fuel including an element constituting the light-emitting particles and a compound serving as an oxidizing agent as starting materials; Spray thermal decomposition method in which a solution containing a metal salt is made into microscopic droplets and then subjected to heat treatment to produce light-emitting particles; It can be carried out by a solid-phase reaction method or the like in which a predetermined powder raw material is mixed and then subjected to heat treatment to produce light emitting particles. Further, liquid synthesis methods such as coprecipitation method, sol-gel method, and hydrothermal synthesis method; It can be carried out by a gas phase synthesis method such as evaporation condensation (PVD) method, vapor phase reaction precipitation (CVD) method, or the like.

In addition, it is preferable to produce light-emitting particles by further passing through a pulverization process in that high light-emitting luminance can be obtained. The pulverization step may be wet pulverization or dry pulverization, but wet pulverization is preferable from the viewpoint of shortening the process because it can be dispersed in a solvent or the like simultaneously with pulverization. In the case of wet grinding, a solvent may be mixed with the raw material powder to perform wet grinding, or a solvent and a resin component may be mixed with the raw material powder to perform wet grinding, or a grinding aid may be used.

Next, a method of manufacturing an inorganic electroluminescent device provided in another aspect of the present invention includes forming a coating layer by coating the surface of the light emitting particles with a metal.

The step may be performed by preparing a coating solution containing the metal, heating the coating solution, and adding the light-emitting particles to the coating solution, but is not limited thereto.

The metal may be copper (Cu), but is not limited thereto.

Next, a method for manufacturing an inorganic EL device provided in another aspect of the present invention includes manufacturing a light emitting device in which a light emitting layer including light emitting particles on which the coating layer is formed is positioned between an anode electrode and a cathode electrode.

The light-emitting particles on which the coating layer is formed may be mixed with a binder. The binder preferably has a high dielectric constant, and for example, a cyanoethyl cellulose resin such as a cyanoethyl cellulose resin, a cyanoethyl fluran resin including a cyanoethyl pullulan resin, and vinylidene fluoride It may be rubber, vinylidene fluoride-based copolymer rubber resin, or cyanoated polyvinyl alcohol, but is not limited thereto.

The mixing ratio of the light emitting particles and the binder is preferably 1:1 to 1:7 based on the mass ratio, and more preferably 1:1 to 1:5.

The anode electrode and the cathode electrode need to make at least one of the two electrodes transparent in order to emit light to the outside.

One transparent electrode among the anode and cathode electrodes is a material thereof, and is ITO, ZnO, AZO, TiO ₂ , SnO ₂ , In ₂ O ₃ , ZnSnO ₃ , AgInO ₂ , Zn ₂ In ₂ O ₅ , Zn ₂ Ga ₂ Materials such as O ₄ may be used, but are not limited thereto, and a generally used transparent electrode may be used.

As the material of the other electrode among the anode and cathode electrodes, metals such as Al, Au, Cu, Ag, Ni, and Pt may be used. When the entire inorganic electroluminescent device is made transparent, the other one The electrode material may be a transparent electrode using a material such as ITO, ZnO, AZO, TiO ₂ , SnO ₂ , In ₂ O ₃ , ZnSnO ₃ , AgInO ₂ , Zn ₂ In ₂ O ₅ , Zn ₂ Ga ₂ O ₄ . In addition, in the case of a high-contrast device, an oxide such as Mo, Ta, or Ti may be deposited to use a black electrode as the other electrode.

In the above step, the light-emitting layer may be formed on one electrode of the light-emitting particles, and may be performed by, for example, spin coating or screen printing, but is not limited thereto, and is not limited to a conventional method used in the art. Can be done by

In addition, the thickness of the emission layer is not particularly limited, but may preferably be 10 nm to 100 μm. When the thickness of the light emitting layer exceeds 100 μm, there is a problem that the driving voltage may increase, and when the thickness of the emission layer is less than 10 nm, there is a problem that insulation breakdown may occur.

In addition, the step may further include forming a hole injection layer between the anode electrode and the light emitting layer.

The hole injection layer is, for example, PEDOT:PSS (poly(3,4-ethylenedioxythiophere poly(styrene sulfonate)), PVK (poly(N-vinylcarbazole)), TFB (poly(9,9-dioctylfluorenyl-2,7-diyl )-co-(4,4'(N-(4-secbutylphenyl))diphenylamine)), a-NPD(N,N'-diphenyl-N,N'-bis(1-naphthyl)-1,1'biphenyl -4,4'-diamine), or TPD(N,N'-Bis-(3-methylphenyl)-N,N'-Bis-phenyl(1,1'-biphenyl)-4,4'-diamine, etc. However, it is not limited thereto.

Since the hole injection layer is formed, holes can more easily flow from the anode to the light emitting particles, and it is possible to prevent the outflow of carriers from the light emitting particles while forming an additional energy barrier.

The above step may be performed by, for example, spin coating or screen printing, but is not limited thereto, and may be performed by a conventional method used in the art.

Next, in the method for manufacturing an inorganic electroluminescent device provided in another aspect of the present invention, an inorganic compound of Formula 2 is formed on at least a portion of the coating layer adjacent to the anode electrode among the coating layers by applying a voltage to the light emitting device, and the And forming an inorganic compound of Formula 3 below on at least a portion of the coating layer adjacent to the cathode electrode among the coating layers.

<Formula 2>

M ² _(1+X) A

<Formula 3>

M ² _(2-X) A

M ² is a metal element, A is at least one element selected from the group consisting of a chalcogen element, and x is 0≦x<0.5.

When voltage is applied in the above step, metal ions in the coating layer may move from the anode side to the cathode by applying a voltage such that the anode side becomes the anode and the cathode side becomes the cathode. As a result, the inorganic compound of Formula 2 is formed on at least a portion of the coating layer adjacent to the anode electrode, and the inorganic compound of Formula 3 is formed on at least a portion of the coating layer adjacent to the cathode electrode.

The applied voltage is preferably 0.1 V to 1000 V, more preferably 0.5 V to 500 V, and more preferably 1 V to 200 V. When the applied voltage exceeds 1000 V, there is a problem that the driving voltage may increase, and when the applied voltage is less than 0.1 V, there is a problem that movement of the metal ions to the cathode side may not be sufficient.

Further, in the above step, voltage application may be performed simultaneously while applying heat.

For example, a voltage may be applied on the hot plate, but the heating method is not limited thereto.

When a voltage is applied while applying heat as described above, the movement of metal ions may become more active.

It is preferable that a p-type semiconductor is formed from the inorganic compound of Formula 2 through the application of voltage in the above step, and an n-type semiconductor is formed of the inorganic compound of Formula 3 above. The inorganic compound of Formula 2 may transfer holes to the light-emitting particles, and the inorganic compound of Formula 3 may transfer electrons to the light-emitting particles. Accordingly, in the light emitting particle, holes and electrons may combine to emit light.

It is preferable that the minimum energy value of the conduction band of the inorganic compound of Formula 2 is greater than the minimum energy value of the conduction band of the light-emitting particles through voltage application in the step. When the minimum energy value of the conduction band of the inorganic compound of Formula 2 is greater than the value of the light emitting particle, an energy barrier may be formed between the inorganic compound of Formula 2 and the light emitting particle, and as a result, the The electrons transferred to the light-emitting particles by the inorganic compound of Formula 3 do not flow toward the anode electrode and may bind with holes in the light-emitting particles.

Hereinafter, the present invention will be described in more detail through Preparation Examples, Examples and Experimental Examples. The scope of the present invention is not limited to specific embodiments, and should be interpreted by the appended claims. In addition, those who have acquired ordinary knowledge in this technical field should understand that many modifications and variations can be made without departing from the scope of the present invention.

<Preparation Example 1> Inorganic electroluminescent device not containing PVK

Mn ions (4 wt%) were added to the ZnS powder to move the emission center to the yellow wavelength region. In addition, the structure of ZnS was transformed from wurtzite to sphalerite through secondary heat treatment.

Next, copper acetate is mixed with deionized water to prepare a coating solution, and then heated at 100°C to activate copper acetate. Thereafter, ZnS:Mn powder is added to the solution and reacted to coat Cu on the ZnS:Mn surface. Thus, Cu-coated ZnS:Mn powder was mixed with 5% ethyl cellulose binder in a ratio of 2:1 to prepare a paste.

Next, the paste was coated on an ITO-coated glass substrate to a thickness of 20 μm by screen printing to form a light emitting layer, and an Al electrode was deposited thereon to manufacture an inorganic electroluminescent device.

<Production Example 2> Inorganic electroluminescent device containing PVK

A light emitting device was manufactured in the same manner as in Preparation Example 1, but a poly-N-vinyl carbazole (PVK, Mn: 25000-50000) layer was formed on the ITO electrode. The PVK solution was prepared by dissolving 0.3 g of PVK in 10 ml of toluene, and after dropping the solution on a substrate, spin-coating at 500 rpm for 5 seconds and 2000 rpm for 15 seconds, and then at 80°C for 10 minutes in a convection oven Dried at the 800 nm thick PVK film was formed on the ITO. A light emitting layer was formed on the PVK film as in Preparation Example 1, and an Al electrode was deposited thereon to manufacture an inorganic EL device.

<Example 1> Application of a formation voltage of 10 V

A forming voltage of 10 V was applied for 10 minutes by connecting the anode to the anode side and the cathode to the cathode side of the inorganic electroluminescent device of Preparation Example 1. The structure of this type of light emitting device is shown in FIG. 2, and its band diagram is shown in FIG.

<Example 2> Application of a formation voltage of 20 V

A forming voltage of 20 V was applied for 10 minutes by connecting the anode to the anode side and the cathode to the cathode side of the inorganic electroluminescent device of Preparation Example 1. The structure of this type of light emitting device is shown in FIG. 2, and its band diagram is shown in FIG.

<Example 3> Application of a formation voltage of 30 V

A forming voltage of 30 V was applied for 10 minutes by connecting the anode to the anode side and the cathode to the cathode side of the inorganic electroluminescent device of Preparation Example 1. The structure of this type of light emitting device is shown in FIG. 2, and its band diagram is shown in FIG.

<Example 4> Application of a formation voltage of 70 V

A formation voltage of 70 V was applied for 10 minutes by connecting the anode to the anode side and the cathode to the cathode side of the inorganic electroluminescent device of Preparation Example 1. The structure of this type of light emitting device is shown in FIG. 2, and its band diagram is shown in FIG.

<Example 5> Application of the formation voltage of 90 V

A forming voltage of 90 V was applied for 10 minutes by connecting the anode to the anode side and the cathode to the cathode side of the inorganic electroluminescent device of Preparation Example 1. The structure of this type of light emitting device is shown in FIG. 2, and its band diagram is shown in FIG.

<Example 6> Application of 110 V formation voltage

A forming voltage of 110 V was applied for 10 minutes by connecting the anode to the anode side and the cathode to the cathode side of the inorganic electroluminescent device of Preparation Example 1. The structure of this type of light emitting device is shown in FIG. 2, and its band diagram is shown in FIG.

<Example 7> Application of a forming voltage of 130 V

A forming voltage of 130 V was applied for 10 minutes by connecting the anode to the anode side and the cathode to the cathode side of the inorganic electroluminescent device of Preparation Example 1 above. The structure of this type of light emitting device is shown in FIG. 2, and its band diagram is shown in FIG.

<Example 8> Application of a formation voltage of 10 V to an inorganic electroluminescent device including PVK

A forming voltage of 10 V was applied for 10 minutes by connecting an anode to the anode side and a cathode to the cathode side of the inorganic electroluminescent device of Preparation Example 2 above. The structure of this type of light emitting device is as shown in FIG. 4 and the band diagram is as in FIG. 5.

<Experimental Example 1>

In Examples 1 to 3, the emission luminance according to the driving voltage was measured and shown in FIG. 10.

As can be seen in FIG. 10, as the formation voltage decreases, the graph is left-shifted. As can be seen in FIG. 11, this means that the smaller the formation voltage is, the smaller the threshold voltage is, that is, the driving voltage can be lowered. In addition, it can be seen that the lower the formation voltage based on the same driving voltage, the higher the emission luminance.

<Experimental Example 2>

In Examples 4 to 7, the emission luminance according to the driving voltage was measured and shown in FIG. 12.

As can be seen in FIG. 12, as in Experimental Example 1, it can be seen that the lower the formation voltage, the left-shifted the graph. This means that as described above, the lower the formation voltage is, the smaller the threshold voltage (FIG. 13) and the higher the emission luminance.

In addition, since Experimental Example 2 was manufactured with a higher formation voltage than that of Experimental Example 1, the threshold voltage was lower in the case of Experimental Example 1, and when compared at the same driving voltage, Experimental Example 1 was compared to Experimental Example 2 in terms of light emission luminance. It can be seen that it is more excellent when comparing FIGS. 12 and 10.

The phenomena that can be confirmed through Experimental Examples 1 and 2 are caused by mass transfer of Cu ions, and when a formation voltage is not applied, a symmetric energy band structure is formed around ZnS as shown in FIG. 8.

However, when a forward voltage is applied, the energy band of the coating layer on the anode side decreases and the energy band of the coating layer on the cathode side increases. Accordingly, when a certain voltage is reached, the conduction band minimum (CBM) of the coating layer on the anode side becomes lower than the CBM of ZnS. Will flow out to the side.

On the other hand, when a high voltage is applied to the device, material transfer of Cu may occur.

As can be seen in FIG. 6, Cu combines with S to form various metal compounds including CuS, Cu _1.96 S, Cu _1.75 S, and Cu ₂ S. The band gap energy (E _g ) of these metal compounds can be, for example, 1.2 eV for Cu ₂ S, 1.35 eV for Cu _1.96 S, 1.75 eV for Cu _1.8 S, 2.11 eV for Cu _1.75 S, and 2.2 eV for CuS. have. This can be seen in FIG. 7.

That is, mass transfer of Cu ions by voltage application induces composition imbalance of Cu _2-x S at both electrodes. This causes a change in the energy barrier of Cu _2-x S at the anode. When Cu _2-x S on the anode side is changed to CuS, CBM increases from -3.6 eV to -1.94 eV, and CuS can become an energy barrier that prevents electrons from moving to the anode electrode beyond the ZnS layer. This can be seen in FIG. 9.

Accordingly, it can be seen that all of Examples 1 to 7 formed an energy barrier capable of preventing the leakage of electrons toward the anode electrode due to the material transfer of Cu, and thus had excellent light emission characteristics.

In addition, it can be seen from FIGS. 10 to 13 that the energy barrier is formed by applying a voltage higher than a certain level and that the lower the formation voltage is, the easier the carrier moves to the emission layer, and thus shows a low threshold voltage and excellent luminous efficiency.

<Experimental Example 3>

In Example 1 and Example 8, the emission luminance according to the driving voltage was measured, and the results are shown in FIG. 14.

It can be seen that the case of Example 8 in which the PVK layer is present has a higher luminance than that of Example 1. This makes it possible to easily supply holes in the light emitting layer by inserting a material layer having a low HOMO (Highest Occupied Molecular Orbital) energy value such as PVK between the anode and the coating layer. PVK has a HOMO value of about -5.6 eV.

As a result, it can be seen from FIG. 14 that the emission luminance is improved by about 29% from 0.49 to 0.63 based on a driving voltage of 2.7 V/µm.

10 anode electrode
20 emitting layer
21 Coating layer adjacent to anode electrode
22 Luminous Particles
23 Coating layer adjacent to cathode electrode
30 cathode electrode
40 hole injection layer
100 inorganic electroluminescent devices

Claims (13)

Anode electrode;
A light-emitting layer formed on the anode electrode and including light-emitting particles, which are inorganic compounds represented by the following Formula 1, and a coating layer coated on the surface of the light-emitting particles; And
Includes; a cathode electrode formed on the emission layer,
At least a portion of the coating layer adjacent to the anode electrode of the coating layer contains an inorganic compound of the following formula (2),
At least a portion of the coating layer adjacent to the cathode electrode among the coating layers comprises an inorganic compound represented by the following formula (3):
<Formula 1>
M ¹ A
<Formula 2>
M ² _(1+x) A
<Formula 3>
M ² _(2-x) A
(In the formulas 1 to 3,
M ¹ is a Group 2 or 12 element,
Wherein A is at least one element selected from the group consisting of chalcogen elements,
M ² is a metal element,
Where x is 0≦x<0.5).
The method of claim 1,
The light emitting particle is an inorganic electroluminescent device, characterized in that at least one selected from the group consisting of ZnS, ZnO, ZnSe, ZnTe, CdS, CdSe, CdTe, CaS, SrS, SrSe and BaS.
The method of claim 1,
The light-emitting particles include a light-emitting center forming element,
The light emitting center forming element is an inorganic electroluminescent device, characterized in that at least one selected from the group consisting of transition metals and rare earth metal elements.
The method of claim 1,
The M ² is an inorganic electroluminescent device, characterized in that copper (Cu).
The method of claim 1,
An inorganic electroluminescent device further comprising a hole injection layer between the anode electrode and the emission layer.
The method of claim 5,
The hole injection layer is PEDOT:PSS (poly(3,4-ethylenedioxythiophere poly(styrene sulfonate)), PVK (poly(N-vinylcarbazole)), TFB (poly(9,9-dioctylfluorenyl-2,7-diyl)-co- (4,4'(N-(4-secbutylphenyl))diphenylamine)), a-NPD(N,N'-diphenyl-N,N'-bis(1-naphthyl)-1,1'biphenyl-4,4 '-diamine), and TPD(N,N'-Bis-(3-methylphenyl)-N,N'-Bis-phenyl(1,1'-biphenyl)-4,4'-diamine selected from the group consisting of Inorganic electroluminescent device, characterized in that at least one type.
The method of claim 1,
The inorganic compound of Formula 2 is a p-type semiconductor, and the inorganic compound of Formula 3 is an n-type semiconductor.
The method of claim 1,
The inorganic electroluminescent device, characterized in that the minimum energy value of the conduction band of the inorganic compound of Formula 2 is greater than the minimum energy value of the conduction band of the light emitting particles.
Preparing light-emitting particles, which are inorganic compounds represented by the following Chemical Formula 1;
Forming a coating layer by coating the surface of the light emitting particles with a metal;
Manufacturing a light emitting device in which a light emitting layer including light emitting particles on which the coating layer is formed is positioned between an anode electrode and a cathode electrode;
Applying a voltage to the light emitting device to form an inorganic compound of the following formula (2) on at least a portion of the coating layer adjacent to the anode electrode of the coating layer,
Forming an inorganic compound represented by the following Formula 3 on at least a portion of the coating layer adjacent to the cathode electrode among the coating layers;
Inorganic electroluminescent device manufacturing method comprising:
<Formula 1>
M ¹ A
<Formula 2>
M ² _(1+X) A
<Formula 3>
M ² _(2-X) A
(In the formulas 1 to 3,
M ¹ is a Group 2 or 12 element,
A is at least one element selected from the group consisting of chalcogen elements,
M ² is a metal element,
Where x is 0≦x<0.5).
The method of claim 9,
Applying a voltage to the light emitting device to form an inorganic compound of the following formula (2) on at least a portion of the coating layer adjacent to the anode electrode of the coating layer,
The step of forming the inorganic compound of Formula 3 below in at least a portion of the coating layer adjacent to the cathode electrode among the coating layers
A method for manufacturing an inorganic electroluminescent device, characterized in that applying heat while simultaneously applying voltage.
The method of claim 9,
The step of manufacturing a light emitting device in which the light emitting layer including the light emitting particles on which the coating layer is formed is located between the anode electrode and the cathode electrode
The method of manufacturing an inorganic electroluminescent device, further comprising forming a hole injection layer between the anode electrode and the emission layer.
The method of claim 9,
The inorganic compound of Formula 2 is a p-type semiconductor, and the inorganic compound of Formula 3 is an n-type semiconductor.
The method of claim 9,
The method of manufacturing an inorganic electroluminescent device, wherein the minimum energy value of the conduction band of the inorganic compound of Formula 2 is greater than the minimum energy value of the conduction band of the light emitting particles.

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