Research Of Photodetector Based On Lead Halide

In recent years,metal halide perovskite,as a new type of photovoltaic material,has excellent photoelectric properties duo to the tunable band gap characteristics,wide absorption spectrum,high power conversion efficiency,high charge carrier mobility,and long charge diffusion length.It shows broad application prospects in photodetectors,light emitting diodes,lasers and solar cells.Benefiting from the low activation energy of metal halide perovskite crystals,the low-temperature solution method can obtain high-quality crystals and high-performance devices.In general,lead halide is the most common metal source material for preparing perovskite.However,in the process of preparing lead halide and lead halide-based perovskite crystals by the solution method,the physical and chemical properties of the solution directly affect the liquid-solid crystal transformation,nucleation,crystal growth,and crystal quality.Therefore,a deeper understanding of the internal relationship between the solid-liquid transformation mechanism of lead halide and lead halide perovskite,and optimizing the growth process of lead halide and related perovskite crystals are the key to preparing high-quality crystals and improving the performance of related photovoltaic devices.This paper focuses on lead halide and lead halide-based perovskite low-dimensional single crystal materials and related devices.We study the simple controllable growth and morphology control methods of lead halide and lead halide perovskite low-dimensional crystals,and explore its two-dimensional fluorescence spectrum and fluorescence lifetime.In addition,photodetectors and flexible photodetectors based on lead halide and lead halide-based perovskite micro-nanocrystals are also prepared.The research contents of this article include:1. Firstly,we use a simple green cooling and hot supersaturated lead iodide?PbI₂? aqueous solution method to controllably prepare PbI₂nanosheets with uniform distribution at room temperature.By controlling the solution temperature,three typical morphologies of PbI₂ crystals are obtained.The evolution of the nucleation rate,number and morphology of the PbI₂crystal are determined by the degree of supersaturation of the solution.Scanning electron microscopy and transmission electron microscopy show that the prepared PbI₂ nanosheets are high quality single crystals.The spatial and time-resolved spectra measurements investigate the fluorescence dynamics of PbI₂ nanosheets.The center region of the prepared PbI₂nanosheets show a higher density of defect states than that at the edges or corners.In addition,the photodetectors based on PbI₂ nanosheets show stable and efficient performance.2. All-inorganic lead halide cesium perovskites have huge potential in the development of optoelectronic devices due to its excellent stability and optoelectronic properties.Here,we study a method for synthesizing pure phase high-quality perovskite CsPb₂Br₅ two-dimensional nanosheets without solvent residue and stack.The results show that the growth temperature is the key factor to determine the evolution of morphology and thickness of CsPb₂Br₅ nanosheets.The lower temperature is beneficial to the formation of nanosheets with more uniform distribution and less stack.The electronic band structure of CsPb₂Br₅ is further studied using first-principles.The spatial and time-resolved spectra measurements further reveal the fluorescence intensity distribution and defect state of nanosheets in different micro-regions.The prepared photodetectors and flexible photodetectors based on CsPb₂Br₅ nanosheets show good photoelectric performance.3. PbBr₂ nanowires with high crystallinity are synthesized by the self-assembly method of aqueous solution at room temperature,and CsPb₂Br₅ nanowires are synthesized based on this precursor PbBr₂ nanowires.The size of PbBr₂nanowires can be controlled by controlling the substrate temperature,and can be quickly converted into CsPb₂Br₅ nanowires.The results show that the growth temperature is the key factor in controlling the morphology of the nanowires.In addition,the two-dimensional fluorescence spectra and fluorescence lifetimes of different regions of 1D CsPb₂Br₅nanowires at room temperature are also studied.At the same time,the photodetectors prepared show excellent photoelectric performance and good stability.