CN1988192A - Flexible single layer white light quantum point electroluminescence device and its preparing method - Google Patents

Abstract

The invention discloses a flexible single-layer white light quantum dot electroluminescent device and a preparation method thereof. The invention uses ZnS, ZnS:Cu/ZnS, ZnS:Mn/ZnS three-color quantum dots as the main luminescent material, and PMMA as the film forming material. Materials are spin-coated on the ITO surface of the PET substrate respectively, and the raw material is made into a film with a certain thickness to obtain a device with the following structure: ITO/PMMA:ZnS, ZnS:Cu/ZnS, ZnS:Mn/ZnS(y nm )/Al(z nm). The white light device adopts a single-layer simple structure, and does not need to separately prepare three primary color light-emitting layers, and carry out cumbersome photolithography processes on them respectively, and has the characteristics of simple preparation process, flexibility, bendability, and good repeatability; Combining the more mature microelectronic etching color filter technology, it is expected to be able to obtain full-color display.

Description

Flexible single-layer white light quantum dot electroluminescent device and its preparation method

【Technical field】

The patent of the present invention relates to a new flat-panel display device—a flexible single-layer white light quantum dot electroluminescent device and its preparation method.

【Background technique】

Flexible electroluminescent display devices use flexible and bendable materials with good light transmission as substrates instead of glass substrates for ordinary devices. Compared with ordinary electroluminescent devices, they are light, thin, vibration-resistant and impact-resistant. Features. Therefore, as a new type of solid flat and flexible display device, flexible electroluminescent display devices have important application prospects in portable display devices and military fields. Although it develops rapidly, the problem of full-color display has always been an important factor restricting its industrialization process.

Quantum dots are quasi-zero-dimensional nano-semiconductor materials, which are composed of a small number of atoms or atomic groups, and usually have a three-dimensional scale of 1 to 10 nm. Due to the influence of size quantum effect and dielectric confinement effect, it shows unique physical and chemical characteristics such as fluorescence characteristics, which makes quantum dots have broad application prospects in optoelectronics and biology. Quantum dot electroluminescent devices have the advantages of low power consumption, high efficiency, fast response and light weight, and can be formed into large-area films. They are photonic devices with great academic value and good commercial prospects. In terms of materials, ZnS-coated CdSe quantum dots are mostly chosen as the light-emitting layer of electroluminescent devices in the world, but cadmium (Cd) is highly toxic and can enter the human body through food, water or air, causing serious poisoning effects on the human body. In view of this, the European Union passed the Restriction of Hazardous Substances in Electrical and Electronic Equipment (RoHS), and banned the use of cadmium (Cadmium) and other substances in electronic products since July 1, 2006. Therefore, the development of new environmentally friendly quantum electrical materials is the development direction of quantum dot electroluminescent devices.

At the same time, most of the traditional methods of obtaining white light in the world are realized through a multi-layer structure, that is, the method of stacking red, green, and blue light-emitting layers, and obtaining white light by mixing the three primary colors. The shortcomings of this method The performance is that the preparation process is complicated, difficult to master, and the cost is high, and the white light chromaticity of the device is easy to change with the change of the external driving voltage. In addition, the multilayer structure is easy to cause self-absorption, and the general quantum efficiency is relatively low.

【Content of invention】

The object of the present invention is to provide a method and device for preparing a flexible single-layer white light quantum dot electroluminescence device in order to overcome the deficiencies of the prior art. The present invention uses trichromatic quantum dots that do not contain toxic components such as cadmium (Cd) and has good thermal stability as the light-emitting layer material, and utilizes the excellent film-forming property of the polymer to realize a single-layer, simple structure, and uniformly luminous flat panel Flexible single-layer white-light quantum dot electroluminescent devices.

The flexible single-layer white light quantum dot electroluminescent device provided by the present invention is characterized in that the light emitting device consists of the following layers from bottom to top:

ITO anode on PET (polyethylene terephthalate) substrate; ZnS, ZnS:Cu/ZnS, ZnS:Mn/ZnS core/shell structure quantum dots with light emitting layer dissolved in PMMA ; Metal Al cathode.

The present invention also provides a method for preparing the above-mentioned flexible single-layer white light quantum dot electroluminescent device, comprising:

(1) The ITO anode etched into a 5mm*60mm strip-shaped PET substrate was repeatedly cleaned in a detergent, then soaked in isopropanol, acetone and chloroform solutions and ultrasonically cleaned, and finally dried in an infrared oven for use ;

(2) PMMA is dissolved in the chloroform solution of 1～2mg/ml, ZnS, ZnS:Cu/ZnS, ZnS:Mn/ZnS quantum dots are 1:1:1～3:1:1 by mass ratio, dissolve In 1-2mg/ml chloroform solution, use the spin coating method to form a film; low speed 1000-1400rpm, film-forming time 10-20s, high-speed 3000-4000rpm, film-forming time 10-30s, place it in a dry place after completion 3 to 10 hours in the device;

(3) The Al cathode is prepared by hanging Al wires about 1-2 cm long on the tungsten alloy furnace wire, and vacuum-depositing a thin layer of strip-shaped Al on the light-emitting layer with the help of a strip-shaped mask plate. The vacuum degree is greater than 8×10 ^-4 Pa., the evaporation current is 10-30A, and the evaporation time is 10-20 minutes;

(4) The device was encapsulated by using polychlorotrifluoroethylene, cutting the polychlorotrifluoroethylene film, and then covering it on the prepared side with the functional layer, exposing the ITO anode and Al cathode, and using epoxy resin Seal the surrounding area with the glue, put it in a desiccator and let it stand for 10-30 minutes to cure the epoxy glue;

(5) One end of all strip-shaped ITO anodes in the device made above is connected to the positive pole of the DC power supply, and one end of all strip-shaped Al cathodes is connected to the negative pole of the DC power supply to obtain a lattice type flexible single-layer white light quantum dot electroluminescent device.

Advantages and positive effects of the present invention: the present invention provides a flexible single-layer white light quantum dot electroluminescent device, the white light device adopts a single-layer simple structure, without the need to separately prepare three primary color light-emitting layers, and to carry out their respective Complicated photolithography process, etc., has the characteristics of simple preparation process and good repeatability; the flexible single-layer white light quantum dot electroluminescent device is suitable as a backlight for this type of display device, and it is also better than the general monochromatic light backlight With less power consumption, it has higher contrast and brightness. And combining it with the relatively mature microelectronic etching color filter film technology, it is expected to be able to obtain full-color display. In addition, the flexible white light quantum dot electroluminescent device basically realizes flexible display and has strong vibration and impact resistance. The device is simply packaged, and the working life of the packaged device has been increased by 13 times, which shows that the Encapsulation is effective.

【Description of drawings】

Figure 1 is a schematic diagram of the specific structure of a flexible single-layer white light quantum dot electroluminescent device;

【Detailed ways】

The present invention uses ZnS, ZnS:Cu/ZnS, ZnS:Mn/ZnS three-color quantum dots as the main luminescent material, and utilizes the excellent film-forming property of the polymer PMMA, uses the polymer PMMA as the film-forming material, and the ITO in the PET layer The surface is spin-coated, and the raw material is made into a thin film with a certain thickness to obtain a device with the following structure: ITO/PMMA:ZnS, ZnS:Cu/ZnS, ZnS:Mn/ZnS(y nm)/Al(z nm); Wherein, 30≤y≤60nm; 60≤z≤150nm, the mass ratio of ZnS, ZnS:Cu/ZnS, ZnS:Mn/ZnS quantum dots in the light emitting layer is between 1:1:1～3:1:1.

Example 1:

(1) The ITO anode etched into a 5mm*60mm strip-shaped PET substrate was repeatedly cleaned in a detergent, then soaked in isopropanol, acetone and chloroform solutions and ultrasonically cleaned, and finally dried in an infrared oven for use ;

(2) PMMA is dissolved in the chloroform solution of 1mg/ml, ZnS, ZnS:Cu/ZnS, ZnS:Mn/ZnS quantum dot is 2:1:1 by mass ratio, is dissolved in the chloroform solution of 1.5mg/ml In the process, the spin coating method is used to form a film; the low speed is 1100rpm, the film forming time is 20s, the high speed is 3000rpm, the film forming time is 30s, and it is placed in the dryer for 10 hours after completion;

(3) The Al cathode is prepared by hanging Al wires about 2 cm long on the tungsten alloy furnace wire, and vacuum-depositing a thin layer of strip-shaped Al on the light-emitting layer with the help of a strip-shaped mask plate, and the vacuum degree is greater than 8× 10 ^-4 Pa., the evaporation current is about 30A, and the evaporation time is about 12 minutes;

(4) The device was encapsulated by using polychlorotrifluoroethylene, cutting the polychlorotrifluoroethylene film, and then covering it on the prepared side with the functional layer, exposing the ITO anode and Al cathode, and using epoxy resin Seal the surrounding area with the glue, put it in a desiccator and let it stand for 30 minutes to cure the epoxy glue;

(5) One end of all strip-shaped ITO anodes in the device made above is connected to the positive pole of the DC power supply, and one end of all strip-shaped Al cathodes is connected to the negative pole of the DC power supply to obtain a lattice white light quantum dot electroluminescent device.

Example 2:

(1) The ITO anode etched into a 5mm*50mm strip-shaped PET substrate was repeatedly cleaned in a detergent, then soaked in isopropanol, acetone and chloroform solutions and ultrasonically cleaned, and finally dried in an infrared oven for use ;

(2) PMMA is dissolved in the chloroform solution of 2mg/ml, ZnS, ZnS:Cu/ZnS, ZnS:Mn/ZnS quantum dot is 3:1:1 by mass ratio, is dissolved in the chloroform solution of 1.5mg/ml In the process, the spin coating method is used to form the film; the low speed is 1300rpm, the film forming time is 20s, the high speed is 3000rpm, the film forming time is 30s, and it is placed in the dryer for 8 hours after completion;

(3) The Al cathode is prepared by hanging Al wires about 2 cm long on the tungsten alloy furnace wire, and vacuum-depositing a thin layer of strip-shaped Al on the light-emitting layer with the help of a strip-shaped mask plate, and the vacuum degree is greater than 8× 10 ^-4 Pa., the evaporation current is about 30A, and the evaporation time is about 15 minutes;

(4) The device was encapsulated by using polychlorotrifluoroethylene, cutting the polychlorotrifluoroethylene film, and then covering it on the prepared side with the functional layer, exposing the ITO anode and Al cathode, and using epoxy resin Seal the surrounding area with the glue, put it in a desiccator and let it stand for 25 minutes to cure the epoxy glue;

(5) One end of all strip-shaped ITO anodes in the device made above is connected to the positive pole of the DC power supply, and one end of all strip-shaped Al cathodes is connected to the negative pole of the DC power supply to obtain a lattice white light quantum dot electroluminescent device.

Claims (4)

1. A flexible single-layer white light quantum dot electroluminescent device, characterized in that the light emitting device consists of the following layers from bottom to top: 1) ITO anode of PET substrate; 2) The luminescent layer is ZnS dissolved in PMMA, ZnS:Cu/ZnS, ZnS:Mn/ZnS three-color quantum dots; 3) Al cathode layer. 2. The flexible single-layer white light quantum dot electroluminescent device according to claim 1, characterized in that the mass ratio of ZnS in the light emitting layer, ZnS:Cu/ZnS, ZnS:Mn/ZnS three-color quantum dots is 1:1 :1～3:1:1, PMMA is the film-forming material, and the thickness y of the light-emitting layer is 30≤y≤60nm. 3. The flexible single-layer white light quantum dot electroluminescent device according to claim 1, characterized in that the thickness z of the Al cathode layer is 60≤z≤150nm. 4. A method for preparing a flexible single-layer white light quantum dot electroluminescent device according to claim 1, characterized in that the method comprises the following steps: (1) The ITO anode etched into a 5mm*60mm strip-shaped PET substrate was repeatedly cleaned in a detergent, then soaked in isopropanol, acetone and chloroform solutions and ultrasonically cleaned, and finally dried in an infrared oven for use ; (2) PMMA is dissolved in the chloroform solution of 1～2mg/ml, ZnS, ZnS:Cu/ZnS, ZnS:Mn/ZnS quantum dots are 1:1:1～3:1:1 by mass ratio, dissolve In 1-2mg/ml chloroform solution, use the spin coating method to form a film; low speed 1000-1400rpm, film-forming time 10-20s, high-speed 3000-4000rpm, film-forming time 10-30s, place it in a dry place after completion 3 to 10 hours in the device; (3) The Al cathode is prepared by hanging Al wires about 1-2 cm long on the tungsten alloy furnace wire, and vacuum-depositing a thin layer of strip-shaped Al on the light-emitting layer with the help of a strip-shaped mask plate. The vacuum degree is greater than 8×10 ^-4 Pa., the evaporation current is 10-30A, and the evaporation time is 10-20 minutes; (4) The device was encapsulated by using polychlorotrifluoroethylene, cutting the polychlorotrifluoroethylene film, and then covering it on the prepared side with the functional layer, exposing the ITO anode and Al cathode, and using epoxy resin Seal the surrounding area with the glue, put it in a desiccator and let it stand for 10-30 minutes to cure the epoxy glue; (5) One end of all strip-shaped ITO anodes in the device made above is connected to the positive pole of the DC power supply, and one end of all strip-shaped Al cathodes is connected to the negative pole of the DC power supply to obtain a lattice type flexible single-layer white light quantum dot electroluminescent device.

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