Preparation Of Perovskite Core-Shell Quantum Dots And Application In Light-Emitting Devices

A new generation of display devices with quantum dot materials as the core light-emitting layer is gradually entering thousands of households.Among them,the core light-emitting materials of quantum dots and their preparation technology still face many scientific and technical problems.Perovskite quantum dots have been favored by researchers in recent years due to their high optical quantum yields,narrow half-peak widths,and tunable emission spectra in the visible light range.However,perovskite quantum dots are easily degraded under air,water,oxygen and light conditions,require harsh preparation conditions,and have poor environmental stability during use;in the traditional method of using quantum dots to prepare optical films,spin coating is usually used.The method coats quantum dots on flexible materials and evaporates the solvent,which leads to the easy precipitation and aggregation of quantum dots,which affects the performance of the device.At present,commercial liquid crystal displays usually use yellow phosphors as the color conversion layer,resulting in a narrow color gamut.The color recognition of the picture is not enough.In view of the above problems,this work follows the research idea of improving the stability of perovskite,improving the preparation process of optical film and applying it to backlight display devices.The silica coating is formed by chemical reaction self-assembly,which isolates the quantum dots from the water and oxygen in the air,which significantly improves the stability of the quantum dots;the influence of reaction time on the thickness of the generated silicon oxide shell layer was systematically explored,and the reason for the improvement of the stability of quantum dots by silicon oxide coating was further explained by DFT calculation;The optical film prepared by the blade coating method can effectively avoid the uneven distribution of quantum dots caused by the spin coating process;the optical film replaces the traditional yellow phosphor as the color conversion layer to construct a liquid crystal module,which enhances the recognition of the picture.This paper mainly includes the following parts:（1）Preparation and performance testing of silica-encapsulated perovskite quantum dots（CsPbX₃@SiO₂）core-shell materials.Core-shell quantum dots are prepared by a modified thermal injection method,and the effect of reaction time on the formation of silicon oxide shell is studied.By changing the halide composition and reaction conditions,core-shell quantum dots with tunable emission spectrum in the visible light range are prepared.Morphological and structural characterizations demonstrate that the prepared perovskite quantum dot core-shell materials are of high quality.Compared with pure quantum dots,the air,water oxygen and light stability of core-shell materials have been greatly improved.The prepared WLED device has good current driving stability,and the color gamut can reach 125%of the NTSC standard.（2）Preparation and performance testing of optical films.Commercial quantum dot films are usually prepared by spin coating and evaporating the surface solvent,but the different polarity of quantum dots and polymers will lead to agglomeration of quantum dots,resulting in uneven distribution of the prepared films and reducing device efficiency.The quantum dots are embedded in the flexible material PET by knife coating,and the prepared optical film has a uniform distribution and strong fluorescence.The double-layer protection allows the quantum dots to maintain 98%of their initial PL intensity after being placed in air for 120 days.The optical film reaches a maximum luminous efficiency of≈34 lm/W when a current of 45 mA is applied,after which the luminous efficiency declines.（3）Construction of liquid crystal module and color rendering performance test.The liquid crystal module consists of a blue chip,an optical film and a liquid crystal display panel.Using green and red optical films as color conversion layers instead of yellow phosphors in commercial liquid crystal displays can limit the avoidance of color segregation caused by anion exchange.Compared to commercial LCD screens,the pictures displayed by our liquid crystal module provide more detail on the color of objects.And the liquid crystal module can achieve a wide color gamut of 128%of the NTSC standard and 98%of the Rec 2020,indicating that the constructed liquid crystal module is an ideal light conversion material for mobile phone screens and has great application potential in the field of color rendering.