阅读说明：本技术 一种量子点发光二极管及其制备方法 (Quantum dot light-emitting diode and preparation method thereof ) 是由 朱佩 向超宇 王雄志 张滔 李乐 于 2018-06-26 设计创作，主要内容包括：本发明公开一种量子点发光二极管及其制备方法,所述量子点发光二极管包括层叠设置的阳极、量子点发光层和阴极,其中,还包括设置于阳极和量子点发光层之间的空穴注入层,所述空穴注入层的材料包括氮化的金属掺杂氧化镍。本发明通过金属掺杂改善氧化镍薄膜的传输性能,并提高其空穴载流子的传输效率,从而提升量子点发光二极管的发光效率；进一步地,金属掺杂氧化镍薄膜经过氮化处理后,使得薄膜内部引入了一定量的氮原子,从而增加了薄膜内部的孔隙率,内部多孔结构可使得氧化镍薄膜的折射率下降,减少了空穴注入层到阳极的出光损失,从而提高量子点发光二极管的透光率。(The invention discloses a quantum dot light-emitting diode and a preparation method thereof, wherein the quantum dot light-emitting diode comprises an anode, a quantum dot light-emitting layer and a cathode which are arranged in a stacked manner, and the quantum dot light-emitting diode also comprises a hole injection layer arranged between the anode and the quantum dot light-emitting layer, wherein the hole injection layer is made of nitrided metal-doped nickel oxide. According to the invention, the transmission performance of the nickel oxide film is improved by metal doping, and the transmission efficiency of hole carriers is improved, so that the luminous efficiency of the quantum dot light-emitting diode is improved; furthermore, after the metal-doped nickel oxide film is subjected to nitridation treatment, a certain amount of nitrogen atoms are introduced into the film, so that the porosity inside the film is increased, the refractive index of the nickel oxide film is reduced due to the internal porous structure, the light-emitting loss from the hole injection layer to the anode is reduced, and the light transmittance of the quantum dot light-emitting diode is improved.)

1. The quantum dot light-emitting diode comprises an anode, a quantum dot light-emitting layer and a cathode which are arranged in a stacked mode, and is characterized by further comprising a hole injection layer arranged between the anode and the quantum dot light-emitting layer, wherein the hole injection layer is made of nitrided metal-doped nickel oxide.

2. The quantum dot light-emitting diode of claim 1, wherein the nitrided metal-doped nickel oxide has a metal-doped oxide with a forbidden band width greater than that of the nickel oxide.

3. The quantum dot light-emitting diode of claim 1, wherein the nitrided metal doped nickel oxide is doped with one of lithium, magnesium or copper.

4. The quantum dot light-emitting diode of claim 1, wherein the nitrided metal-doped nickel oxide has a metal molar doping amount of 1-5%.

5. The quantum dot light-emitting diode of claim 1, wherein the hole injection layer has a thickness of 30-150 nm.

6. A preparation method of a quantum dot light-emitting diode is characterized by comprising the following steps:

providing an anode;

providing a metal-doped nickel oxide material, and preparing a hole injection layer formed by the metal-doped nickel oxide material on an anode;

mixing oxygen and nitrogen according to a preset volume ratio to form mixed fast flow, and performing laser gas nitriding treatment on the hole injection layer to obtain a hole injection layer with a porous structure inside;

preparing a quantum dot light emitting layer on the hole injection layer with the porous structure inside;

and preparing a cathode on the quantum dot light-emitting layer to obtain the quantum dot light-emitting diode.

7. The method for preparing the quantum dot light-emitting diode of claim 6, wherein the method for preparing the metal-doped nickel oxide material comprises the following steps:

mixing metal-doped oxide and nickel oxide according to the weight ratio of 0.01-0.05: mixing and grinding the mixture according to the molar ratio of 0.95 to 0.99 to obtain mixed powder;

and sintering, cooling, dry-pressing and re-sintering the mixed powder in sequence to obtain the metal-doped nickel oxide material.

8. The method of claim 7, wherein the sintering temperature is 800-1000 ℃ and/or the sintering time is 6-10 h.

9. The method of claim 6, wherein the oxygen and nitrogen are mixed in a ratio of 1: 6-1: 10 volume ratio to form a mixed velocity stream.

10. The method as claimed in claim 6, wherein the preheating temperature of the mixed beam is 200-400 ℃ and/or the laser scanning speed is 100-300 m/min.

Technical Field

The invention relates to the field of quantum dot light-emitting diodes, in particular to a quantum dot light-emitting diode and a preparation method thereof.

Background

In recent years, with the rapid development of display technology, quantum dot light emitting diodes (QLEDs) having semiconductor quantum dot materials as light emitting layers have received much attention. The QLED has good characteristics of high color purity, high luminous efficiency, adjustable luminous color, stable device and the like, so that the QLED has wide application prospect in the fields of flat panel display, solid state lighting and the like.

Conventional quantum dot light emitting diode structures typically include: the conventional ITO electrode is generally provided with a hole transport layer formed by a polyethylene dioxythiophene/polystyrene sulfonate (PEDOT: PSS) material, wherein the HOMO energy level of the PEDOT: PSS is well matched with the work function of the ITO so that hole injection and transmission can be effectively realized, but the PEDOT: PSS presents acidity, so that the electrode is corroded in long-term use of the device, and the luminous efficiency and the service life of the QLED are reduced.

The nickel oxide film is a good P-type semiconductor material, and the crystal lattice of the nickel oxide film exists in the presence of Ni²⁺The vacancy ensures that the hole conducting performance is better, but the surface resistance of the nickel oxide is larger, so that the transmission efficiency of hole carriers is influenced, and the light transmission of the nickel oxide is poorer, so that the luminous efficiency of a bottom light-emitting device is influenced.

Accordingly, the prior art is yet to be improved and developed.

Disclosure of Invention

In view of the above-mentioned shortcomings of the prior art, the present invention aims to provide a quantum dot light emitting diode and a method for manufacturing the same, which aims to solve the problems of poor light transmittance and low light emitting efficiency of the conventional quantum dot light emitting diode.

The technical scheme of the invention is as follows:

the quantum dot light-emitting diode comprises an anode, a quantum dot light-emitting layer and a cathode which are arranged in a stacked mode, and further comprises a hole injection layer arranged between the anode and the quantum dot light-emitting layer, wherein the hole injection layer is made of nitrided metal-doped nickel oxide.

A preparation method of a quantum dot light-emitting diode comprises the following steps:

providing an anode;

providing a metal-doped nickel oxide material, and preparing a hole injection layer formed by the metal-doped nickel oxide material on an anode;

mixing oxygen and nitrogen according to a preset volume ratio to form mixed fast flow, and performing laser gas nitriding treatment on the hole injection layer to obtain a hole injection layer with a porous structure inside;

preparing a quantum dot light emitting layer on the hole injection layer with the porous structure inside;

and preparing a cathode on the quantum dot light-emitting layer to obtain the quantum dot light-emitting diode.

Has the advantages that: the quantum dot light-emitting diode provided by the invention comprises a hole injection layer, wherein the hole injection layer is made of nitrided metal-doped nickel oxide, the transmission performance of a nickel oxide film can be improved through metal doping, and the transmission efficiency of a hole carrier of the nickel oxide film is improved, so that the light-emitting efficiency of the quantum dot light-emitting diode is improved; furthermore, after the metal-doped nickel oxide film is subjected to nitridation treatment, a certain amount of nitrogen atoms are introduced into the film, so that the porosity inside the film is increased, the refractive index of the nickel oxide film is reduced due to the internal porous structure, the light-emitting loss from the hole injection layer to the anode is reduced, and the light transmittance of the quantum dot light-emitting diode is improved.

Drawings

Fig. 1 is a schematic structural diagram of a quantum dot light emitting diode according to a preferred embodiment of the invention.

Detailed Description

The invention provides a quantum dot light-emitting diode and a preparation method thereof, and the invention is further described in detail below in order to make the purpose, technical scheme and effect of the invention clearer and clearer. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Nickel oxide due to its special lattice structure and Ni²⁺The vacancy shows better hole conductivity, so the nickel oxide film can be used as a better P-type semiconductor material. However, since the sheet resistance of nickel oxide is large, this greatly affects the hole carrier transport efficiency thereof; and the light transmittance of the nickel oxide is poor, which affects the light extraction efficiency of the bottom emission device.

Based on this, the invention provides a quantum dot light emitting diode, as shown in fig. 1, comprising an anode, a quantum dot light emitting layer and a cathode which are arranged in a stacked manner, wherein the quantum dot light emitting diode further comprises a hole injection layer arranged between the anode and the quantum dot light emitting layer, and the material of the hole injection layer comprises nitrided metal-doped nickel oxide.

According to the invention, the nickel oxide is doped with the metal, so that the valence band of the nickel oxide is deepened, which is beneficial to injecting holes from the anode into the nickel oxide film, meanwhile, the element content lattice structure of the nickel oxide film can be changed by a small amount of metal doping, the carrier transmission efficiency is improved, and the doped metal can provide more carriers, so that the nickel oxide obtains more carrier migration.

Furthermore, the material of the hole injection layer comprises nitrided metal-doped nickel oxide, namely the metal-doped nickel oxide film is subjected to nitriding treatment, so that a certain amount of nitrogen atoms are introduced into the film, the porosity inside the film is increased, the refractive index of the nickel oxide film is reduced due to an internal porous structure, the light extraction loss from the hole injection layer to the anode is reduced, and the light transmittance of the quantum dot light-emitting diode is improved.

Specifically, the metal-doped nickel oxide film is processed by adopting a laser gas nitriding technology, nitrogen is activated by laser, nitrogen molecule bonds are opened after nitrogen molecules absorb laser photons, and nitrogen atoms can be combined with nickel atoms in the nickel oxide activated by laser melting to form nickel nitride. Therefore, in the invention, the nickel oxide in the nitrided metal-doped nickel oxide film is partially nitrided, and the stress and the conductivity of the metal-doped nickel oxide film can be further improved after nitridation treatment, so that the stability of the quantum dot light-emitting diode is improved.

Therefore, the nitrided metal-doped nickel oxide is used as the hole injection layer material of the quantum dot light-emitting diode provided by the invention, so that the light-emitting efficiency of the quantum dot light-emitting diode can be effectively improved, and the light transmittance and the stability of the quantum dot light-emitting diode can be improved.

Preferably, in the nitrided metal-doped nickel oxide, the forbidden bandwidth of the metal-doped oxide is greater than that of the nickel oxide. The hole transport efficiency can be improved by increasing the forbidden band width of nickel oxide, and in order to extend the forbidden band width of nickel oxide to a larger direction, metal with the forbidden band width larger than that of nickel oxide needs to be doped correspondingly.

By way of example, the present embodiment prefers one of lithium, magnesium, or copper as the doping metal, but is not limited thereto. Further, lithium or magnesium is preferred as the doping metal, since the forbidden bandwidth of nickel oxide is 3-4eV, the forbidden bandwidths of magnesium oxide and lithium oxide reach 7.8eV and 5.1eV, respectively, and the lattice structures of magnesium oxide and lithium oxide are extremely similar to those of the nickel oxide, the hole transport efficiency can be effectively improved by doping the nickel oxide with the metal magnesium or the metal lithium.

Preferably, in the nitrided metal-doped nickel oxide, the molar doping amount of the doping metal is 1 to 5%, that is, the molar ratio of the oxide of the doping metal to the nickel oxide is 0.01 to 0.05: 0.95-0.99. When the molar doping amount of the doping metal is less than 1%, the forbidden bandwidth of the nickel oxide is not enough to extend, and the carriers provided by the doping metal are less, so that the hole transmission efficiency of the nickel oxide film is not obviously improved; when the molar doping amount of the doping metal is more than 5%, distortion of the nickel oxide thin film is caused, resulting in deterioration of structural properties of the thin film.

Preferably, the thickness of the hole injection layer is 30 to 150 nm.

PreferablyThe quantum dot light-emitting diode also comprises a hole transport layer arranged between the hole injection layer and the quantum dot light-emitting layer, and the material of the hole transport layer can be selected from NiO, CuO, CuS and VO_x、WO_x、MoO_xOne or more of; it can also be selected from one or more of PEDOT, PSS, TFB, PVK, Poly-TPD, TCTA, CBP, mCP, HAT-CN, NPB. More preferably, the hole transport layer has a thickness of 30 to 50 nm.

Preferably, the quantum dot light emitting diode further comprises an electronic function layer disposed between the quantum dot light emitting layer and the cathode, the electronic function layer comprising at least one of an electron transport layer and an electron injection layer. In other words, the electron functional layer may be an electron transport layer; an electron injection layer may also be used; it may further include an electron transport layer and an electron injection layer, wherein the electron injection layer is stacked with the cathode.

Preferably, the material of the electron injection layer may be selected from metals such as Ca and Ba having a low work function, and may also be selected from CsF, LiF, CsCO₃The compound can be other electrolyte type electron injection layer material.

Preferably, the material of the electron transport layer may be selected from materials having good electron transport properties, such as, but not limited to, n-type ZnO, TiO₂、Fe₂O₃、SnO₂、Ta₂O₃One or more of AlZnO, ZnSnO, InSnO and the like. More preferably, the material of the electron transport layer is n-type ZnO. Further preferably, the thickness of the electron transport layer is 50 to 150 nm.

Preferably, the material of the quantum dot light emitting layer (QDs) may be selected from one or more of common red, green and blue quantum dots. The quantum dot light-emitting layer material comprises but is not limited to CdSe/ZnS, CdS/ZnSe, CdSN/ZnSe and other core-shell quantum dots or quantum dot materials based on a gradient shell. Further preferably, the thickness of the quantum dot light emitting layer is 30 to 60 nm.

Preferably, the material of the anode can be selected from one or more of ITO, FTO, ATO and AZO. Further preferably, the thickness of the anode is 20 to 100 nm.

Preferably, the material of the cathode can be selected from one or more of Ag, Al, Cu, Au.

The invention also provides a preparation method of the quantum dot light-emitting diode, which comprises the following steps:

providing an anode;

providing a metal-doped nickel oxide material, and preparing a hole injection layer formed by the metal-doped nickel oxide material on an anode;

mixing oxygen and nitrogen according to a preset volume ratio to form mixed fast flow, and performing laser gas nitriding treatment on the hole injection layer to obtain a hole injection layer with a porous structure inside;

preparing a quantum dot light emitting layer on the hole injection layer with the porous structure inside;

and preparing a cathode on the quantum dot light-emitting layer to obtain the quantum dot light-emitting diode.

The invention needs to prepare a metal-doped nickel oxide material in advance before preparing the quantum dot light-emitting diode, and the preparation method of the metal-doped nickel oxide material specifically comprises the following steps: firstly, mixing the oxide of the metal to be doped with nickel oxide powder according to the weight ratio of 0.01-0.05: mixing and grinding the mixture according to the molar ratio of 0.95 to 0.99 to obtain mixed powder; then sending the mixed powder into a tubular furnace for primary sintering treatment, wherein the furnace temperature in the tubular furnace is increased from room temperature to 800-1000 ℃ of sintering temperature, and the temperature is kept for 6-10 h; and when the mixed powder is cooled to below 200 ℃, taking out the mixed powder, then carrying out dry pressing forming on the mixed powder by using a powder tablet press under the condition that the pressure is 5-20MPa, finally sending the formed powder into a tubular furnace to carry out secondary sintering treatment under the same conditions as the primary sintering treatment, and obtaining the corresponding metal-doped nickel oxide material after sintering.

Preferably, the purity of the oxide of the metal to be doped and the purity of the nickel oxide are both more than 99.9%.

As one embodiment, the cleaned substrate is placed in a magnetron sputtering machine for ITO film plating to be used as an anode; then preparing a metal-doped nickel oxide film, namely a hole injection layer, on the surface of the anode by adopting a radio frequency sputtering or solution method; in order to improve the stability and light transmittance of the QLED, the metal-doped nickel oxide film is subjected to nitridation treatment before the quantum dot light-emitting layer is prepared on the hole injection layer.

In the embodiment, the metal-doped nickel oxide film is subjected to nitridation treatment by adopting a laser gas nitridation technology to obtain a hole injection layer with a porous structure inside. Specifically, the substrate prepared with the metal-doped nickel oxide film is placed under a laser, and the activated atmosphere in the laser processing process is mainly nitrogen and oxygen; preferably, the laser is operated according to the ratio of oxygen: the volume ratio of nitrogen is 1: 6-1: 10, in the atmosphere proportion, due to the introduction of a certain amount of nitrogen atoms, the porosity inside the film is increased, the refractive index of the nickel oxide film can be reduced due to an internal porous structure, the light-emitting loss from a hole injection layer to an anode is reduced, and therefore the light transmittance of the quantum dot light-emitting diode is improved. Furthermore, the laser gas nitriding treatment can also improve the stress of the metal-doped nickel oxide film and improve the conductivity of the metal-doped nickel oxide film.

Preferably, the preheating temperature of the mixed beam stream is 200-400 ℃.

Preferably, the laser scanning speed is 100-300m/min, and the laser power density is 0.56-5.5 x 10⁵W/cm²。

Preferably, the spot diameter of the laser is 1-3mm, and the laser wavelength is 10.6 microns.

And further, preparing a quantum dot light-emitting layer on the hole injection layer with the porous structure inside, and preparing a cathode on the quantum dot light-emitting layer after the quantum dot light-emitting layer is annealed to obtain the QLED.

The technical solution of the present invention will be described in detail by specific examples.