Application Of Cs-based Metal Halide Perovskites In Optoelectronic Devices

In recent years,the research of metal halide perovskite materials has been a hot trend in the field of optoelectronics,and the majority of researchers have applied their excellent photoelectric properties to different photoelectric devices.Such as:solar cells,light-emitting diodes,photodetectors,X-ray detectors and lasers.Although such materials have obvious advantages,it is necessary to continuously try and explore suitable materials in order to prepare high-performance and sustainable optoelectronic devices.For example,we can choose the perovskite structure transformation from three-dimensional to low-dimensional（3D-0D）,and also choose the low-toxic/non-toxic green transformation.For perovskite solar cells（PSCs）,they have many defects and poor stability,so it is necessary to further reduce the device defects and improve stability.For X-ray detectors,the X-ray photon energy is huge,so the efficiency and stability of practical application should be considered.For photodetectors,most materials contain toxic lead element,so they need to develop in the direction of green environmental protection.Therefore,this paper focuses on the selection of different metal halide perovskite materials,through a series of structural design to prepare efficient,stable and environmentally friendly photoelectric devices.The specific work is as follows:1.The interface engineering concept is introduced that uses Cs Pb Br₃ and Cs Pb Cl₃colloidal quantum dots（QDs）to reduce energy loss of Cs Pb I₃ PSCs.The QDs interface layer not only passivates defects of thin film in the surface and grain boundary,but also optimizes the energy level structure of the device,and further reduces defects of the device and improves environmental stability.The results show that the power conversion efficiency of PSCs increases from 17.26%to 18.89%,and performance of the optimized device is still better than pristine device after 150 hours in natural environment.2.The two-dimensional（2D）CsPb₂Br₅ powder was prepared by a simple solution precipitation method,the Cs Pb₂Br₅ powder was pressed into wafer and applied to X-ray detector for the first time.The high polymer was added to the powder to improve the viscosity and make the pressed wafer more compact.At the same time,the wafer is pressed under heating condition,so that the crystallinity of wafer is enhanced and the surface of wafer is smooth and compact.The results show that the device exhibits high sensitivity(8379μC Gy_air^-1 cm^-2)and low detection limit(2.66 n Gy_air s^-1).3.Lead-free 2D CsBi₃I₁₀ material was first used on flexible substrate and prepared into thin film by a simple one-step solution spin-coating method.The film with high coverage and large grain size was prepared by heating substrate method.The results indicate that the Cs Bi₃I₁₀ flexible film photodetector has good photoelectric performance,high operational stability,good flexible stability,and dynamic imaging ability.