Colloidal quantum dots have continuous illuminating light, high purity of emitted light, and high conversion efficiency. As a core material for next-generation lighting and display technology, relatively mature preparation techniques have been obtained. Quantum dots are usually not directly usable because quantum dots are relatively fragile. Because of the large surface energy of nanometers, clusters can occur, causing fluorescence quenching and energy transfer easily. At the same time, the colloidal layer is easily eroded, leaving defect levels. , forming a non-radiative transition channel, causing fluorescence decay. Conventional physicochemical environments cause fluorescence quenching of quantum dots. Therefore, how to use quantum dots is currently a hot and critical issue.
In the actual application process, the encapsulation of quantum dot materials is often achieved in the following two ways:
1. Disperse the quantum dots into the polymer matrix to obtain a fluorescent composite material to form a simple "quantum dot-carrier material (PMMA)" structure (see Reference 1 for details), using a remote packaging method, but because the quantum dots will be It is incompatible with the surface ligand and dielectric layer, and slowly agglomerates in PMMA, so that the fluorescence wavelength of the quantum dot is red-shifted, and the fluorescence efficiency is obviously degraded. The carrier material (PMMA) has poor water and oxygen barrier ability, and the water and oxygen small molecule penetrates. It is also easy to etch the surface of the quantum dot, causing the fluorescence to decay.
2. The surface is organically modified with a surfactant. According to Reference 2, in order to prevent the agglomeration of quantum dots, the surface of the quantum dots is transaminated, which can enhance the compatibility of the quantum dots with the surrounding dielectric layer. , effectively reduce the agglomeration and water and oxygen erosion. However, this method is easy to damage the surface ligand of the quantum dot and affect the initial fluorescence efficiency of the quantum dot.
For quantum dot and silica gel direct composite packaging, the colloidal ligands in the outer layer of the quantum dots are incompatible with the silica gel. In particular, when some surface ligands contain sulfur (S) elements, they act on the platinum (Pt) catalyst in the silica gel, which affects the curing of the silica gel, rendering it incapable of curing. When non-cured silica gel is used, clusters often appear due to compatibility problems between surface ligands and silica gel. For quantum dot polymer materials, the fluorescence properties are affected by the initiator, polymer active sites and polymer chemical polymerization, causing the quantum dot polymer to decay or quench. For the direct treatment of quantum dot surface, such as growth of silica, surface amination modification, etc., the fluorescence quenching of quantum dots is caused mainly by the replacement of surface ligands, and the surface of quantum dots is eroded by the penetration of small molecules such as water molecules such as oxygen. , producing luminescent defects, resulting in a decline in fluorescence efficiency.
Therefore, the use of high luminous efficiency and high stability quantum dots or quantum dot polymers in devices must address the following issues:
1. Quantum dot materials cannot destroy their own luminous efficiency.
2. The quantum dot carrier environment should be compatible with the surface of the quantum dot to prevent the quantum dots from agglomerating and the ligands falling off.
3. Set a barrier layer to prevent small molecules (water vapor and oxygen) from eroding the surface of the quantum dots.
Tianjin Zhonghuan Quantum Technology Co., Ltd. has long been committed to the research, development, production and sales of quantum dot materials. In December 2015, the company proposed a quantum dot fluorescent microsphere structure for packaging, which includes fluorescent quantum dots and nanogrids. The mesoporous particulate material and the barrier layer of the lattice structure are as shown in Fig. 1, wherein the fluorescent quantum dots are distributed in the mesoporous particulate material, and the barrier layer is coated on the outer surface of the mesoporous particulate material. By chemical and non-chemical means, the fluorescent quantum dots enter the mesoporous particulate material, and in the non-polar solvent, the surface structure of the colloidal fluorescent quantum dots is not destroyed, and the fluorescence efficiency of the fluorescent quantum dots is maintained. The structure can effectively alleviate the agglomeration of the quantum dots, and the surface coated barrier layer can prevent the erosion of small molecules of water and oxygen, and improve the compatibility and stability of the quantum dot fluorescent microspheres. In the same year, the company also submitted the patent application to the US Patent Office, and was authorized in February 2017. See Figure 2 for details. The quantum dot fluorescent microspheres are the company's independent intellectual property products.
Figure 1. Schematic diagram of quantum dot fluorescent microspheres
Figure 2, patent power of attorney
references:
1. J. Eun-Pyo, S. Woo-Seuk, L. Ki-Heon, Y. Heesun, Nanotechnology2013,24, 045607 (9 pp.).
2. E. Jang, S. Jun, H. Jang, J. Llim, B. Kim, Y. Kim, Advanced Materials 2010, 22, 3076.
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