KR20130047943A - Quantum dot light emitting display device and method for fabricating the same - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a quantum light emitting display device and a method for manufacturing the same, wherein the light emitting efficiency can be improved by forming a quantum light emitting layer using a quantum dot including a ligand having electron and hole transporting ability. The substrate; A first electrode and a hole transport layer sequentially stacked on the substrate; A quantum light emitting layer formed on the hole transport layer; And an electron transport layer and a second electrode sequentially stacked on the quantum light emitting layer, wherein the quantum light emitting layer comprises a first quantum light emitting layer made of a first quantum dot having a hole transport ligand and a second quantum dot having an electron transport ligand The quantum light emitting layer is a structure in which at least one alternately is stacked.

Description

QUANTUM DOT LIGHT EMITTING DISPLAY DEVICE AND METHOD FOR FABRICATING THE SAME

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a quantum light emitting display device, and more particularly, to a quantum light emitting display device and a manufacturing method thereof capable of improving light emission efficiency.

Video display devices that implement a variety of information as screens are core technologies of the information and communication era, and are being developed in a direction of thinner, lighter, portable and high performance. BACKGROUND ART As a flexible display that can be bent in pursuit of space and convenience is demanded, an organic light emitting display device that controls the amount of light emitted from the organic light emitting layer as a flat panel display device has recently been in the spotlight.

In general, an organic light emitting display device uses an organic light emitting material as a material of an emission layer, and an organic light emitting diode (OLED) using an organic light emitting material realizes a single color such as white, red, and blue according to the type of device. However, there is a limit to expressing a lot of light colorfully.

Accordingly, recently, a quantum light emitting display device using a quantum dot (QD), which is a semiconductor nanoparticle, has been developed. Quantum dots with a diameter of nanometers emit light when electrons in an unstable state descend from the conduction band to the valence band. Smaller particles of the quantum dots generate shorter wavelengths of light, and larger particles generate long wavelengths of light. This is a unique electrical and optical characteristic that differs from conventional semiconductor materials.

Therefore, by adjusting the size of the quantum dot to represent the visible light of the desired wavelength, it is possible to implement a variety of colors at the same time by different quantum dot and quantum dot components of different sizes. In addition, since the color reproducibility is good and the luminance is not behind the light emitting diode, it has been spotlighted as a material that can compensate for the shortcomings of a light emitting diode (LED), which is attracting attention as a next-generation light source.

Hereinafter, a structure of a general quantum light emitting display device will be described.

1 is a cross-sectional view of a general quantum light emitting display device.

As shown in FIG. 1, a general quantum light emitting display device includes a substrate 100, a cathode 10 and an anode 50 facing each other on the substrate 100, and a quantum emission layer formed between the anode 10 and the cathode 50 ( 30), the hole transport layer 20 formed between the anode 10 and the quantum light emitting layer 30, and the electron transport layer 40 formed between the quantum light emitting layer 30 and the cathode 50.

The quantum light emitting layer 30 is formed of a plurality of quantum dots 30a, and although not illustrated, the quantum dots 30a include a core, a shell, and a ligand. The shell, which forms the surface of the core and envelops the light, serves to protect the core. In addition, a ligand is formed on the surface of the shell to surround the shell, thereby helping the quantum dot 30a to be well dispersed in the solvent when the quantum light emitting layer 30 is formed.

In the quantum light emitting display device as described above, the hole transport layer 20 transports and injects holes from the anode 10 to the quantum dots 30a of the quantum light emitting layer 30, and electrons injected through the cathode 50 are transferred to the electron transport layer ( 40 is injected into the quantum light emitting layer 30 through. The holes and electrons injected into the quantum light emitting layer 30 sequentially communicate with the ligand and the shell, and then meet and emit light at the core. However, in general, since the ligand is formed of an organic material having no conductivity, the probability of bonding holes and electrons in the core is low, and thus the luminous efficiency of the quantum light emitting display device is reduced.

The present invention has been made to solve the above problems, and by forming a quantum light emitting layer using a quantum dot containing a ligand having electrons and hole transporting capacity, the quantum light emitting display device and the manufacturing thereof can be improved To provide a method, the purpose is.

A quantum light emitting display device of the present invention for achieving the above object, a substrate; A first electrode and a hole transport layer sequentially stacked on the substrate; A quantum light emitting layer formed on the hole transport layer; And an electron transport layer and a second electrode sequentially stacked on the quantum light emitting layer, wherein the quantum light emitting layer comprises a first quantum light emitting layer made of a first quantum dot having a hole transport ligand and a second quantum dot having an electron transport ligand The quantum light emitting layer is a structure in which at least one alternately is stacked.

The lowest layer of the quantum light emitting layer is a first quantum light emitting layer, and the highest layer of the quantum light emitting layer is a second quantum light emitting layer.

The hole transport ligands include aryl amines.

The aryl amine is tri aryl amine.

The electron transport ligand includes a heterocyclic compound.

The heterocyclic compound includes a heteroatom selected from oxygen, sulfur, nitrogen, and silicon.

In addition, a method of manufacturing a quantum light emitting display device of the present invention for achieving the same object comprises the steps of forming a first electrode and a hole transport layer on a substrate in turn; Forming a quantum light emitting layer on the hole transport layer; And sequentially forming an electron transporting layer and a second electrode on the quantum light emitting layer, wherein the forming of the quantum light emitting layer comprises: a first quantum light emitting layer comprising a first quantum dot having a hole transporting ligand and an electron transporting ligand; A second quantum light emitting layer made of two quantum dots is formed by alternately stacking at least one time.

In the forming of the quantum light emitting layer, a first quantum light emitting layer is formed on the lowest layer, and a second quantum light emitting layer is formed on the top layer of the quantum light emitting layer.

The forming of the quantum light emitting layer may include applying a mixture obtained by dispersing a first quantum dot having the hole transport ligand in a solvent on the hole transport layer and volatilizing the solvent to form the first quantum light emitting layer; And applying a mixture obtained by dispersing a second quantum dot having the electron transport ligand in a solvent, onto the first quantum light emitting layer, and volatilizing the solvent to form the second quantum light emitting layer.

The hole transport ligands include aryl amines.

The aryl amine is tri aryl amine.

The electron transport ligand includes a heterocyclic compound.

The heterocyclic compound includes a heteroatom selected from oxygen, sulfur, nitrogen, and silicon.

As described above, the quantum light emitting display device and the manufacturing method thereof according to the present invention alternately alternately at least one time between the first quantum light emitting layer made of the first quantum dots having the hole transport ligand and the second quantum light emitting layer made of the second quantum dots having the electron transport ligand. By forming a stacked quantum light emitting layer, holes and electrons can be smoothly injected into the quantum light emitting layer, thereby improving luminous efficiency.

In particular, the first quantum light emitting layer is formed on the lowest layer of the quantum light emitting layer, and the second quantum light emitting layer is formed on the top layer of the quantum light emitting layer to facilitate the injection of holes from the hole transport layer below the quantum light emitting layer, and from the electron transport layer on the quantum light emitting layer. The injection of electrons can be made smooth.

1 is a cross-sectional view of a typical quantum light emitting display device.
2 is a cross-sectional view of a quantum light emitting display device of the present invention.
3A is a detailed cross-sectional view of the first quantum dot of FIG. 2.
3B is a detailed cross-sectional view of the second quantum dot of FIG. 2.
4 is a cross-sectional view of a quantum light emitting display device of the present invention having a quantum light emitting layer including a plurality of first and second quantum light emitting layers.
5A through 5D are cross-sectional views illustrating a method of manufacturing the quantum light emitting display device of the present invention.

Hereinafter, a quantum light emitting display device and a method of manufacturing the same will be described in detail with reference to the accompanying drawings.

2 is a cross-sectional view of the quantum light emitting display device of the present invention, FIG. 3A is a detailed cross-sectional view of the first quantum dot of FIG. 2, and FIG. 3B is a specific cross-sectional view of the second quantum dot of FIG. 2. 4 is a cross-sectional view of a quantum light emitting display device of the present invention having a quantum light emitting layer including a plurality of first and second quantum light emitting layers.

As illustrated in FIG. 2, the quantum light emitting display device of the present invention is formed on the substrate 200, the first electrode 110, the hole transport layer 120, and the hole transport layer 120 that are sequentially formed on the substrate 200. On the quantum light emitting layer 130 and the quantum light emitting layer 130 including a first quantum light emitting layer made of a first quantum dot 170 having a transport ligand and a second quantum light emitting layer made of a second quantum dot 180 having an electron transport ligand. The electron transport layer 140 and the second electrode 150 formed in this order are included.

Specifically, the type of the substrate 200 is not particularly limited and may be variously possible, and a glass substrate, a plastic substrate, or a silicon substrate may be used. Although not illustrated, a thin film transistor is formed on the substrate 200, and the drain electrode and the first electrode 110 of the thin film transistor are electrically connected to each other.

The first electrode 110 is an anode (Tin Oxide (TO), Indium Tin Oxide (ITO), Indium Zinc Oxide (IZO), Indium Tin Zinc Oxide (Indium Tin) It is formed of a transparent conductive material such as Zinc Oxide (ITZO), and the like, and light generated in the quantum light emitting layer 130 may emit light through the first electrode 110.

The hole transport layer (HTL) 120 formed on the first electrode 110 is used to facilitate the injection of holes into the quantum light emitting layer 130, but is not illustrated, but the hole and the first electrode 110 are not shown. A hole injection layer (HIL) may be further formed between the transport layers 120.

The quantum light emitting layer 130 has a structure in which a first quantum light emitting layer made of a first quantum dot 170 having a hole transport ligand and a second quantum light emitting layer made of a second quantum dot 180 having an electron transport ligand are sequentially stacked.

As mentioned above, common quantum dots have ligands formed from organic materials that are not conductive. Therefore, in the conventional quantum light emitting display device, the probability of combining holes and electrons in the core is low, and thus the light emission efficiency is reduced.

Accordingly, the quantum light emitting display device according to the present invention has a structure in which a first quantum light emitting layer including a first quantum dot 170 having a hole transport ligand and a second quantum light emitting layer consisting of a second quantum dot 180 having an electron transport ligand are sequentially stacked. By forming the quantum light emitting layer 130, holes and electrons can be injected into the core smoothly to improve the luminous efficiency.

In detail, as illustrated in FIG. 3A, the first quantum dot 170 includes a core 170a, a shell 170b surrounding the core 170a, and a hole transport ligand 170c surrounding the shell 170b. The core 170a emits light, and the shell 170b formed around the core 170a and formed on the surface of the core 170a serves to protect the core 100a.

The core 170a and the shell 170b may be made of group II-VI, III-V, III-VI, VI-IV, or IV compound semiconductors of the periodic table, for example, II-VI compound Is a compound selected from CdSe, CdS, CdTe, ZnO, ZnSe, ZnS, ZnTe, HgSe, HgTe, CdZnSe, and the like. AlP, AlN, AlAs, AlSb, CdSeTe, ZnCdSe and the like. And group VI-IV is a compound selected from PbSe, PbTe, PbS, PbSnTe, Ti ₂ SnTe ₅ and the like.

The hole transport ligand 170c formed on the surface of the shell 170b so as to surround the shell 170b disperses the first quantum dot 170 in a solvent and at the same time receives holes transferred from the hole transport layer 120. It is for injecting well into the core 170a. Specifically, the hole transport ligand 170c includes aryl amine (Aryl Amine) having excellent hole transport ability, and may be preferably formed of a tri aryl amine-based material. At this time, the tri aryl amine series is α-NPD, β-NPD, TPD, CBP, BMA-nT, TBA, o-TTA, p-TTA, m-TTA, spiro-TPD, TPTE, etc. It is a substance.

As shown in FIG. 3B, the second quantum dot 180 also includes a core 180a, a shell 180b surrounding the core 180a, and an electron transport ligand 180c surrounding the shell 180b. Specifically, the electron transport ligand 18c includes a heterocyclic compound having excellent electron transport ability. Heterocyclic compound is a compound having a ring-like structure, the atoms constituting the ring contains a hetero atom other than carbon, hetero atoms are oxygen (O), sulfur (S), nitrogen (N), silicon ( Si) and the like.

Meanwhile, as illustrated in FIG. 4, the quantum light emitting layer 130 includes a first quantum light emitting layer made of the first quantum dot 170 having the hole transport ligand 170c and a second quantum dot 180 having the electron transport ligand 180c. The second quantum light emitting layer may have a structure in which a plurality of turns are alternately stacked.

In particular, in this case, it is preferable that the first quantum light emitting layer is formed on the lowest layer of the quantum light emitting layer 130, and the second quantum light emitting layer is formed on the uppermost layer of the quantum light emitting layer 130. This is to smoothly inject holes from the hole transport layer 120 under the quantum light emitting layer 130 and to smoothly inject electrons from the electron transport layer 140 on the quantum light emitting layer 130.

Referring back to FIG. 2, the electron transport layer (ETL) 140 formed on the quantum light emitting layer 130 is for smoothly injecting electrons into the quantum light emitting layer 130. An electron injection layer (EIL) may be further formed between the 140 and the second electrode 150. The second electrode 150 is a cathode, and at least one selected from the group consisting of magnesium (Mg), silver (Ag), aluminum (Al), calcium (Ca), and alloys thereof having a low work function. It can be formed as. In particular, the second electrode 150 may be formed of a metal material having a high reflectance such that light emitted from the quantum light emitting layer 130 is reflected to emit light downward through the substrate 200.

As described above, the quantum light emitting display device according to the present invention includes a first quantum light emitting layer made of the first quantum dots 170 having the hole transport ligand 170c and a second quantum dot 180 having the electron transport ligand 180c. The quantum light emitting layer 130 having a structure in which two quantum light emitting layers are alternately stacked at least once is formed, so that holes and electrons are smoothly injected into the cores of the first and second quantum dots 170 and 180 to improve light emission efficiency. Can be.

Hereinafter, a method of manufacturing the quantum light emitting display device according to the present invention will be described in detail.

5A through 5D are cross-sectional views illustrating a method of manufacturing the quantum light emitting display device of the present invention.

First, as shown in FIG. 5A, the first electrode 110 and the hole transport layer 120 are sequentially formed on the substrate 200. Although not shown, a thin film transistor including a semiconductor layer including an active layer and an ohmic contact layer, a gate electrode, a source electrode, and a drain electrode is formed on the substrate 200, and is electrically connected to the drain electrode of the thin film transistor. 1 electrode 110 is formed.

The first electrode 110 is an anode, and tin oxide (TO), indium tin oxide (ITO), and indium zinc oxide (IZO) by a deposition method such as a sputtering method. And a transparent conductive material such as indium tin zinc oxide (ITZO). The hole transport layer 120 may be formed on the first electrode 110, and although not illustrated, a hole injection layer may be further formed between the first electrode 110 and the hole transport layer 120.

The hole transport layer 120 and the hole injection layer respectively form a solution process such as ink jet, nozzle coating, spray coating, roll printing, and the like. It is formed by the (Soluble Process) method.

4B and 4C, the quantum light emitting layer 130 is formed on the hole transport layer 120 by the above-described solution process method. Specifically, the quantum light emitting layer 130 is a second quantum made of a second quantum dot 180 having an electron transport ligand 180c on the first quantum light emitting layer made of the first quantum dot 170 having the hole transport ligand 170c. The light emitting layers are sequentially stacked.

Specifically, as shown in FIG. 4B, the mixture of the first quantum dot 170 having the hole transporting ligand 170c in a solvent such as hexane, toluene, chloroform, and the like is dispersed in the hole transport layer 120. ) And the solvent is volatilized to form the first quantum light emitting layer.

Then, a mixture obtained by dispersing the second quantum dot 180 having the electron transport ligand 180c in the above solvent is applied onto the first quantum light emitting layer, and the solvent is volatilized to form the second quantum light emitting layer. The first and second quantum light emitting layers may be formed to be alternately stacked at least once, in which case, the first quantum light emitting layer is formed on the lowest layer of the quantum light emitting layer 130, and the first and second quantum light emitting layers are formed on the top layer of the quantum light emitting layer 130. It is preferable that 2 quantum light emitting layers are formed. This is to smoothly inject holes from the hole transport layer 120 under the quantum light emitting layer 130 and to smoothly inject electrons from the electron transport layer on the quantum light emitting layer 130.

4D, the electron transport layer 140 and the second electrode 150 are sequentially formed on the quantum light emitting layer 130 by a deposition method such as a sputtering method. Although not shown, an electron injection layer is further formed between the electron transport layer 140 and the second electrode 150 to allow electrons to be injected into the quantum light emitting layer 130 from the second electrode 150, which is a cathode.

As described above, the quantum light emitting display device according to the present invention includes a first quantum light emitting layer made of the first quantum dots 170 having the hole transport ligand 170c and a second quantum dot 180 having the electron transport ligand 180c. By forming the quantum light emitting layer 130 having a structure in which the two quantum light emitting layers are alternately stacked at least once, holes and electrons are smoothly injected into the quantum light emitting layer 130, thereby improving light emission efficiency.

While the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. Will be apparent to those of ordinary skill in the art.

110: first electrode 120: hole transport layer
130: quantum light emitting layer 140: electron transport layer
150: second electrode 170: first quantum dot
170a, 180a: core 170b, 180b: shell
170c: hole transport ligand 180c: electron transport ligand
200: substrate

Claims (13)

Board;
A first electrode and a hole transport layer sequentially stacked on the substrate;
A quantum light emitting layer formed on the hole transport layer; And
An electron transport layer and a second electrode sequentially stacked on the quantum light emitting layer,
The quantum light emitting layer has a structure in which a first quantum light emitting layer made of a first quantum dot having a hole transport ligand and a second quantum light emitting layer made of a second quantum dot having an electron transport ligand are alternately stacked at least one or more times. Device. The method of claim 1,
And the lowest layer of the quantum light emitting layer is a first quantum light emitting layer, and the highest layer of the quantum light emitting layer is a second quantum light emitting layer. The method of claim 1,
And the hole transport ligand comprises aryl amine. The method of claim 3, wherein
And the aryl amine is a triaryl amine. The method of claim 1,
The electron transport ligand is a quantum light emitting display device comprising a heterocyclic compound. The method of claim 5, wherein
The heterocyclic compound may include a hetero atom selected from oxygen, sulfur, nitrogen, and silicon. Sequentially forming a first electrode and a hole transport layer on the substrate;
Forming a quantum light emitting layer on the hole transport layer; And
Forming an electron transport layer and a second electrode on the quantum light emitting layer in sequence;
Forming the quantum light emitting layer is formed by alternately stacking at least one or more first quantum light emitting layer consisting of a first quantum dot having a hole transport ligand and a second quantum light emitting layer consisting of a second quantum dot having an electron transport ligand. A manufacturing method of a quantum light emitting display device. The method of claim 7, wherein
The forming of the quantum light emitting layer may include forming a first quantum light emitting layer on a lowermost layer and forming a second quantum light emitting layer on a top layer of the quantum light emitting layer. The method of claim 7, wherein
The forming of the quantum light emitting layer may include applying a mixture obtained by dispersing a first quantum dot having the hole transport ligand in a solvent on the hole transport layer and volatilizing the solvent to form the first quantum light emitting layer; And
Applying a mixture obtained by dispersing a second quantum dot having the electron transport ligand in a solvent, onto the first quantum light emitting layer, and volatilizing the solvent to form the second quantum light emitting layer. Method of manufacturing the device. The method of claim 7, wherein
And the hole transport ligand comprises an aryl amine. 11. The method of claim 10,
And the aryl amine is triaryl amine. The method of claim 7, wherein
The electron transport ligand is a method of manufacturing a quantum light emitting display, characterized in that it comprises a heterocyclic compound. 13. The method of claim 12,
The heterocyclic compound includes a hetero atom selected from oxygen, sulfur, nitrogen, and silicon.

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