KR20080074548A - Quantum-dot electroluminescence device and method of manufacturing the same - Google Patents

Abstract

A quantum-dot light emitting device is provided to realize excellent durability and driving characteristics, and to enable application of a simple fabrication process at room temperature under ambient pressure without using any expensive equipment. A quantum-dot light emitting device comprises: a first inorganic material(144); and a quantum-dot light emitting layer(140) formed of a plurality of quantum dots(142) enclosed inside the first inorganic material by the same. The first inorganic material includes a metal oxide compound or metal sulfide compound. The first inorganic material preferably includes at least one inorganic compound selected from the group consisting of magnesium oxide(MgO), zinc oxide(ZnO), zinc sulfide(ZnC) and yttrium oxide(Y2O3).

Description

Quantum dot light emitting device and method of manufacturing the same {Quantum-dot electroluminescence device and method of manufacturing the same}

1 is a cross-sectional view conceptually illustrating a quantum dot light emitting device according to an exemplary embodiment of the present invention.

2 is a cross-sectional view conceptually illustrating a structure of a quantum dot according to another exemplary embodiment of the present invention.

3 to 6 are cross-sectional views conceptually illustrating a method of manufacturing a quantum dot light emitting device according to an embodiment of the present invention.

7 is a graph showing current-voltage (I-V) characteristics of a quantum dot light emitting device manufactured according to an embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

100: quantum dot light emitting device

110: base substrate 120: first electrode layer

130: p-type material layer 140: quantum dot light emitting layer

142: quantum dot 144: first inorganic

145: metal ion 150: n-type material layer

160: second electrode layer 250: another type of quantum dot

151: core portion 152: shell portion

The present invention relates to a quantum dot light emitting device and a method of manufacturing the same, to a quantum dot light emitting device excellent in durability and driving stability and to a method of manufacturing the quantum dot light emitting device excellent in process efficiency.

A quantum dot electroluminescence (QD-EL) device or a ND-EL (nanodot electroluminescence) device, when a power is applied, emits light in a specific wavelength region depending on the size of a quantum dot, which is an inorganic semiconductor particle. Refers to an element capable of emitting light.

In general, organic materials necessary for wet synthesis and dispersion of quantum dots have a negative effect on device stability and driving stability after device fabrication. Conventional quantum dot light emitting devices may be manufactured by arranging quantum dots on a hole transport layer (HTL) and vacuum depositing monomolecular organic material as an electron transport layer (ETL). Recently, a wet process may be used in which a precursor solution of an n-type inorganic material is coated and then heat treated to form a thin film to manufacture a light emitting device.

However, in the case of forming an n-type inorganic thin film using an inorganic precursor by a wet process, quantum dot particles are dissolved in an organic solvent, thereby causing a phenomenon in which a film formed of quantum dot particles is damaged.

In order to solve this problem, the inventors of the present application use an organic cross-linking agent that has a functional group on both sides of the chain-shaped molecule to bind between neighboring quantum dots. We have also developed a technology that enables the manufacturing of wet devices by maintaining the quantum confinement-effect and ensuring the chemical and mechanical stability of the quantum dot thin film.

However, the device fabrication process and device structure (for example, ITO / polymer (ETL) / quantum dot / inorganic / metal electrode) ("/" mark is a symbol indicating that the stacked, and at the same time the interface between different materials In the case of ITO / polymer or quantum dot / inorganic material, due to the weakness of hetero-junction interface of organic-inorganic material, delamination between interfaces may occur due to current by electrons or holes, It may cause device degradation.

Accordingly, an object of the present invention is to provide a quantum dot light emitting device that is excellent in durability and driving characteristics, to solve the problems of the prior art described above.

Another object of the present invention is to provide a manufacturing method capable of easily manufacturing the quantum dot light emitting device under normal temperature and pressure without using expensive equipment.

A quantum dot light emitting device according to an aspect of the present invention for achieving the object of the present invention as described above, a plurality of quantum dots, which are bound within the first inorganic material by the first inorganic material, and the first inorganic material It has a quantum dot light emitting layer made of.

As a specific example, the quantum dot light emitting device is formed on the first electrode layer, the p-type material layer for transporting and transferring holes to the quantum dot light emitting layer when the power is applied, the p-type material layer The quantum dot light emitting layer formed on and generating light when power is applied, the n-type material layer formed on the quantum dot light emitting layer and transferring and transferring electrons to the quantum dot light emitting layer when power is applied, and the n- And a second electrode layer formed on the layer of material material and corresponding to the first electrode layer.

A method of manufacturing a quantum dot light emitting device according to an aspect of the present invention includes forming a p-type material layer on a first electrode layer, forming a quantum dot light emitting layer, and forming an n-type material layer on the quantum dot light emitting layer. Forming, and forming a second electrode layer on the n-type material layer.

Specifically, forming the quantum dot light emitting layer comprises i) arranging a plurality of quantum dots on the p-type material layer, ii) adding a metal salt solution to the quantum dots to form a metal ion atmosphere around the quantum dots And iii) adding a basic solution to the quantum dots under the metal ion atmosphere. The meaning of “add” includes various embodiments such as a method of directly immersing a member in a solution, a method of applying a solution, and the like.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings and the contents described in the accompanying drawings, but the present invention is not limited or limited to the embodiments. Like reference numerals in the drawings denote like elements.

1 is a cross-sectional view conceptually illustrating a quantum dot light emitting device according to an exemplary embodiment of the present invention.

Referring to FIG. 1, the quantum dot light emitting device 100 according to the present embodiment includes a base substrate 110, a first electrode layer 120, a p-type material layer 130, a quantum dot light emitting layer 140, and n−. And a second emission layer 150 and a second electrode layer 160.

As the base substrate 110, a substrate made of a transparent material such as glass is used. Light generated by the quantum dot light emitting device 100 may be emitted to the outside through the base substrate 110.

The first electrode layer 120 and the second electrode layer 160 are disposed at the outermost sides of the quantum dot light emitting device 100 except for the base substrate 110. In the present embodiment, the first electrode layer 120 is made of a transparent thin film such as indium tin oxide (ITO). On the other hand, the second electrode layer 160 is made of a metal such as aluminum (Al).

In the present embodiment, a single-side display device is conceivable. Alternatively, the second electrode layer 160 may also be formed of a transparent electrode, thereby employing the quantum dot light emitting device according to the present invention. In this case, the base substrate 110 may also be disposed on the second electrode layer 160 to protect the second electrode layer 160 as a transparent electrode.

The p-type material layer 130 is composed of a p-type polymer layer or a p-type inorganic layer. In some cases, it may be composed of a p-type low molecular organic material.

The p-type material layer 130 functions as a hole transport layer (HTL) or a hole transport layer, such as in an OLED device. In the present embodiment, the p-type material layer 130 is configured as a single layer, but may be made of a plurality of different material layers to more efficiently implement the hole transport or hole transport function.

As the p-type polymer layer, a polymer compound layer such as PPV, PVK, or PEDOT may be used. In addition, as the p-type inorganic layer 130, an inorganic layer such as nickel oxide (NiO) or copper thiocyanate (I) (CuSCN) may be used.

It is preferable to configure the entire quantum dot light emitting device 100 only with inorganic materials excluding organic materials, and thus, it is preferable to apply an inorganic layer as the p-type inorganic layer 130. Do.

When the quantum dot light emitting layer 140 is supplied with power from the outside and an electric field is formed by the first electrode layer 120 and the second electrode layer 160, light is generated according to the electro-optical characteristics of the quantum dot 142. Let's do it. By adjusting the particle size of the quantum dot 142, it is possible to implement a variety of colors.

The quantum dot light emitting layer 140 is made of only inorganic material. That is, the quantum dot emission layer 140 includes a plurality of quantum dots 142, which are semiconductor inorganic particles, and the quantum dot 142, and a first inorganic material for implementing the quantum dot emission layer 140 as an inorganic layer. 144. That is, the quantum dots 142 are embedded in the first inorganic material 144 by forming a kind of hybrid with the first inorganic material 144. A detailed method for implementing the quantum dot light emitting layer 140 as a layer composed only of an inorganic component will be described later. The quantum dots 142 may be fixed and stabilized by the first inorganic material 144. The quantum dot light emitting layer 140 has all of the light emitting regions made of an inorganic material, and thus has excellent heat resistance.

As the first inorganic material, a metal oxide compound or a metal sulfide compound is used, and the two series compounds may be used simultaneously. Specifically, as the first inorganic material, inorganic compounds such as magnesium oxide (MgO), zinc oxide (ZnO), zinc sulfide (ZnS), and yttrium oxide (Y ₂ O ₃ ) may be used, and the compounds may be used alone or in combination. It can be used by a combination of two or more.

As the quantum dot 142, inorganic particles made of cadmium selenide (CdSe) and the like are used. Specifically, the quantum dot 142 may be CdSe, CdTe, CdS, ZnSe, ZnTe, ZnS, InP, GaP, GaInP _2, or the like. The compound may include a semiconductor compound selected from Cu-doped materials and Mn-doped materials. In the present exemplary embodiment, the quantum dot 142 is made of a single material. Alternatively, the quantum dot 142 may be made of two or more materials. That is, by including two or more kinds of materials, it is possible to enhance the durability and heat resistance of the quantum dot 142 itself.

2 is a cross-sectional view conceptually illustrating a structure of a quantum dot according to another exemplary embodiment of the present invention.

Referring to FIG. 2, the quantum dot 250 according to another embodiment of the present invention includes a core part 251 and a shell part 252. As the core part 251, the above-described cadmium selenide may be used. The shell part 252 is formed on the surface of the core part 250 to surround the core part 251. The shell portion 252 may be made of an inorganic compound such as zinc sulfide (ZnS) or cadmium sulfide (CdS). That is, the quantum dot 250 is a kind of coating film is formed on the outside of the core portion 251, it is very excellent in durability and heat resistance.

Referring back to FIG. 1, an n-type material layer 150 is formed on the quantum dot light emitting layer 140. As the n-type material layer, a monomolecular layer composed of a single molecule, an n-type polymer layer, an n-type inorganic layer, or the like may be used.

As the single molecule, a single molecule of Alq3 series may be used, and as the n-type polymer layer, a known polymer compound having an electron transport or transfer function may be used.

The n-type inorganic layer may be formed of an inorganic compound such as titanium dioxide (TiO ₂ ), zinc oxide (ZnO), zirconium oxide (ZrO ₂ ), or the like.

As described above, the quantum dot light emitting device 100 according to the present embodiment is preferably made of only inorganic material.

Accordingly, the quantum dot light emitting layer 140 may include a first inorganic material, the n-type material layer 150 may be formed of a second inorganic material, and the p-type material layer 130 may be formed of a third inorganic material. . In the quantum dot light emitting device according to the present invention, organic matters are excluded, and problems caused by organic materials such as device degradation can be solved, and stability of the quantum dot light emitting devices can be improved.

The second electrode layer 160 is formed on the n-type material layer 150. When the second electrode layer 160 is supplied with power from the outside, the second electrode layer 160 operates together with the first electrode layer 120 to inject holes and electrons into the quantum dot light emitting device, so that the hole-electrons are in the quantum dot light emitting layer 140. It serves to generate light by recombination of.

In the present embodiment, as the second electrode layer 160, a metal thin film layer such as aluminum (Al) is used. However, in order to apply the quantum dot light emitting device 100 to a double-sided light emitting display device or the like, the second electrode layer 160 may be formed of a transparent electrode like the first electrode layer 120 described above. In this case, the quantum dot light emitting device 100 may further include a protective substrate such as a transparent substrate made of glass to protect the second electrode layer 160.

Hereinafter, a method of manufacturing the quantum dot light emitting device 100 will be described in detail.

3 to 6 are cross-sectional views conceptually illustrating a method of manufacturing a quantum dot light emitting device according to an embodiment of the present invention.

FIG. 3 is a cross-sectional view conceptually illustrating forming a p-type material layer on a base substrate and arranging a plurality of quantum dots on the p-type material layer.

The p-type material layer 130 is formed on the base substrate 120. The p-type material layer 130 may be formed in various ways according to the material properties of the p-type material. For example, a sputtering method, a vacuum vapor deposition method (chemical, physical), a wet method, etc. are mentioned. In addition, when the p-type material is an inorganic material, the p-type material layer 120 may be formed by a chemical method using an inorganic precursor compound.

A plurality of quantum dots 142 are arranged on the p-type material layer 120.

4 is an enlarged view illustrating an enlarged portion “A” of FIG. 2.

In the wet synthesis and dispersion process of the quantum dots 142, organic materials such as organic solvents are inevitably used. Accordingly, surface ligands 143, such as surfactants, used in the synthesis of the quantum dots 142 are distributed on the surface of the quantum dots 142. Such organic compounds are also preferably removed by the process to be described later.

5 is a cross-sectional view conceptually showing a state in which a metal ion is formed by applying a metal salt to quantum dots.

Referring to FIG. 5, metal ions 145 penetrate around the quantum dots 142 to form an ionic atmosphere. To this end, the base substrate 110 on which the quantum dots 142 are arranged is supported in a predetermined time in an aqueous solution or an alcohol solution in which the metal ions 145 are dissolved at a constant concentration. In the present embodiment, a method of supporting the quantum dots 142 in the aqueous solution or the alcohol solution, which is the metal salt solution, may be used. Alternatively, the metal ion solution may be supplied to the surface to form a metal ion atmosphere.

With the metal salt solution, it is possible to use a magnesium salt such as, for example, can be used a metal salt solution, such as magnesium acetate _{[Mg (OOCCH 3) 2]} .

FIG. 6 is a cross-sectional view illustrating the formation of an inorganic layer around the quantum dots by adding a basic solution to the quantum dots in the metal ion atmosphere.

Referring to FIG. 6, metal ions (eg, infiltrated) are treated by treating a quantum dot 142 in the aforementioned ionic atmosphere with a basic aqueous solution such as sodium hydroxide (NaOH), ammonium hydroxide (NH ₄ OH) or an alcohol solution. Mg ^{+ 2),} for the inorganic metal oxide 144 (e. g., may be converted to such as MgO). In this process, the metal oxide 144 generated between the quantum dots 142 performs a function of a spacer, which bonds between the quantum dots 142 and at the same time serves as an electrical insulator. Ensure that the quantum-confinement effect is maintained. As a result, the quantum dot emission layer 140 including the quantum dots 142 and only the inorganic material may be formed.

Meanwhile, when the above process is completed, the organic compound 143 distributed on the surface may also be removed.

To summarize the chemical reaction during the formation of the quantum dot light emitting layer 140 is shown in Scheme 1 below. Scheme 1 below illustrates a reaction scheme when magnesium acetate is used as the metal salt solution.

Since the quantum dot light emitting layer 140 formed as described above is chemically and mechanically stable, various organic and inorganic films may be formed on the quantum dot light emitting layer 140 by a vacuum deposition method, a sol-gel method, or a wet method. Therefore, the n-type material layer 150 to be formed on the quantum dot light emitting layer 140 may be stably formed in various ways. In particular, by using a precursor solution of the n-type inorganic material, the n-type material layer 150 may be easily formed as an inorganic material by using a wet thin film solution process under normal temperature and atmospheric pressure conditions without additional equipment.

According to the above method, it is possible to prevent problems such as damage to the quantum dot 142 layer, which is generated when the n-type material layer 150 is formed by the conventional wet method.

On the other hand, when the inorganic material is applied to all of the p- type material layer 130, the n- type material layer 150 and the quantum dot light emitting layer 140 as described above, the organic-free quantum dot light emitting device Inorganic-based optical devices, such as these, can be manufactured.

7 is a graph showing current-voltage (I-V) characteristics of a quantum dot light emitting device manufactured according to an embodiment of the present invention.

In order to examine the current-voltage characteristics, PPV is used as the p-type material layer 130, amorphous titanium dioxide (TiO ₂ ) produced by a wet process is used as the n-type material layer 150, and the light emitting layer is used. As a quantum dot light emitting device consisting of a quantum dot layer (CdSe-MgO) stabilized with MgO was used.

Referring to FIG. 7, the turn-on voltage showed a low value of less than 3 V, and showed stable light emission characteristics above the turn-on voltage. This is equivalent to or lower than the turn-on voltage of a typical organic electroluminescent device (OLED).

As described above, according to the present invention, the quantum dot light emitting layer is made of only an inorganic material, thereby providing a quantum dot light emitting device having excellent durability, heat resistance, and driving stability.

In addition, according to the present invention, it is possible to manufacture a quantum dot light emitting device in which there is no organic substance that negatively affects the driving and stability of the device. Furthermore, when the p-type material layer and the n-type material layer are composed of inorganic materials as described above, the entire quantum dot light emitting device may be manufactured as an inorganic material device.

In addition, according to the present invention, the quantum dots can be fixed and stabilized with inorganic materials, and at the same time, the quantum confinement effect of the quantum dots can be effectively maintained.

By using the method of manufacturing the quantum dot light emitting device according to the present invention, it is possible to easily manufacture the quantum dot light emitting device in room temperature, atmospheric pressure or air without using expensive equipment, thereby creating various types of device fabrication and application fields. . Therefore, the manufacturing method of the present invention may be effectively applied in the field of photovoltaic cells, solar cells, optical sensors, etc. in addition to the light emitting device field.

As described above, although the present invention has been described with reference to limited embodiments and drawings, the present invention is not limited to the above embodiments, and those skilled in the art to which the present invention pertains various modifications and variations from such descriptions. This is possible. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined by the claims below and equivalents thereof.

Claims (18)

First inorganic material; And A quantum dot light emitting device having a quantum dot light emitting layer made up of a plurality of quantum dots contained in the first inorganic material by the first inorganic material. The method of claim 1, The first inorganic material is a quantum dot light emitting device comprising a metal oxide (metal oxide) compound or a metal sulfide (metal sulfide) compound. The method of claim 2, The first inorganic material includes at least one inorganic compound selected from the group consisting of magnesium oxide (MgO), zinc oxide (ZnO), zinc sulfide (ZnS), and yttrium oxide (Y ₂ O ₃ ). device. The method of claim 1, The quantum dot is characterized in that it comprises a semiconductor compound selected from the group consisting of CdSe, CdTe, CdS, ZnSe, ZnTe, ZnS, InP, GaP, GaInP ₂ , Cu-doped material of the compounds and Mn-doped material of the compounds Quantum dot light emitting device. The method of claim 1, The quantum dot is a quantum dot light emitting device comprising a core portion and a shell portion (shell) coupled to the core portion to surround the core portion. The method of claim 5, The core portion is made of cadmium selenide (CdSe), the shell portion is quantum dot light emitting device, characterized in that consisting of zinc sulfide (ZnS) or cadmium sulfide (CdS). The method of claim 1, The quantum dot light emitting device, A first electrode layer; A p-type material layer formed on the first electrode layer and transporting and transferring holes to the quantum dot light emitting layer when power is applied; The quantum dot light emitting layer formed on the p-type material layer and generating light when power is applied; An n-type material layer formed on the quantum dot light emitting layer and transferring and transferring electrons to the quantum dot light emitting layer when power is applied; And And a second electrode layer formed on the n-type material layer and corresponding to the first electrode layer. The method of claim 7, wherein The first electrode layer is a quantum dot light emitting device, characterized in that the indium tin oxide (ITO) thin film. The method of claim 7, wherein And the p-type material layer is a p-type polymer layer or a p-type inorganic layer. The method of claim 9, The p-type inorganic layer is a quantum dot light emitting device, characterized in that made of nickel oxide (NiO) or copper thiocyanate (I) (CuSCN). The method of claim 7, wherein The n-type material layer is any one selected from the group consisting of a monomolecular layer, an n-type polymer layer and an n-type inorganic layer. The method of claim 11, The n-type inorganic layer is a quantum dot light emitting device, characterized in that made of any one material selected from the group consisting of titanium dioxide (TiO ₂ ), zinc oxide (ZnO) and zirconium oxide (ZrO2). The method of claim 7, wherein And the p-type material layer and the n-type material layer are each composed of a second inorganic material and a third inorganic material. Forming a p-type material layer on the first electrode layer; i) arranging a plurality of quantum dots on the p-type material layer; ii) adding a metal salt solution to the quantum dots to form a metal ion atmosphere around the quantum dots; And iii) adding a basic solution to the quantum dots under the metal ion atmosphere; Forming an n-type material layer on the quantum dot light emitting layer; And Forming a second electrode layer on the n-type material layer. The method of claim 14, And the p-type material layer is formed using a predetermined p-type inorganic material. The method of claim 14, The metal salt solution is a method of manufacturing a quantum dot light emitting device comprising a magnesium salt. The method of claim 16, The magnesium salt is a magnesium acetate [Mg (OOCCH ₃ ) ₂ ] method of manufacturing a quantum dot light emitting device. The method of claim 14, Wherein the n-type material layer is formed by a solution process using an n-type inorganic precursor compound.

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