Preparation Of One-Dimensional Organic-inorganic Lead Halide Perovskite And Application Of Photodetector

Photodetector is a device that can convert optical signals into electrical signals,and has a wide range of applications in the fields of optical communications,spectroscopy,environmental monitoring,and biosensors.In recent years,lead halide perovskites have been regarded as next-generation semiconductor materials due to their high absorption coefficient,wide light absorption range,long carrier diffusion length,high carrier mobility,and solution processability.Compared with traditional inorganic semiconductor materials,based on the advantages of lead halide perovskites,low-cost,large-area,flexible,and multifunctional lead halide perovskites photodetectors can be prepared.Among the numerous structures of lead halide perovskite（single crystal,thin film,low-dimensional perovskite）,one-dimensional lead halide perovskite has a high specific surface area and one-dimensional confinement effect,and is a favorable material for the preparation of photodetectors.However,high-quality one-dimensional lead halide perovskites are not easy to prepare,and photo-generated carriers are easy to recombine on the surface.Therefore,the high-efficiency synthesis of high-quality one-dimensional lead halide perovskite and the structural design to improve carrier separation and transmission are of great significance to the application and development of one-dimensional lead halide perovskite detectors.In this dissertation,a new synthesis method of one-dimensional organic-inorganic lead halide perovskite microwires is introduced.The microwires are designed to construct a core-shell heterojunction structure that is conducive to carrier separation and transmission,and successfully prepared high-performance photodetector.The main research work is as follows:1.Preparation of one-dimensional（CH₃）₂C=NHCH₃PbBr₃ lead halide perovskite microwires.The CH₃NH₃PbBr₃ lead halide perovskite single crystal reacts with CH₃COCH₃.This reaction leads to the formation of centimeter-level（CH₃）₂C=NHCH₃PbBr₃ lead halide perovskite microwires through the A-site cation induce phase transformation,and the yield is as high as 80%.Studies have confirmed that in order to react with the A-site cation CH₃NH₃⁺in the CH₃NH₃PbBr₃ lead halide perovskite single crystal,the organic reagent must contain functional groups that can react with CH₃NH₃⁺,and the molecular size of the organic reagent must also be appropriate.Single crystal X-ray diffraction test shows that（CH₃）₂C=NHCH₃PbBr₃lead halide perovskite microwire belongs to the trigonal crystal system,with a unique face-sharing triangular prism crystal structure.2.The design of one-dimensional（CH₃）₂C=NHCH₃PbBr₃/CH₃NH₃PbBr₃core-shell heterojunction wirowires.Through research,it is found that in the presence of water,the A-site cation reaction is reversible,and the surface of the（CH₃）₂C=NHCH₃PbBr₃ lead halide perovskite microwire will slowly transform into CH₃NH₃PbBr₃ lead halide perovskite single crystal.Thereby forming a（CH₃）₂C=NHCH₃PbBr₃/CH₃NH₃PbBr₃ core-shell heterojunction wirowires with a CH₃NH₃PbBr₃ lead halide perovskite layer（surface）and a（CH₃）₂C=NHCH₃PbBr₃lead halide perovskite layer（inside）.With the formation of the core-shell heterojunction,the luminescence intensity derived from the CH₃NH₃PbBr₃ lead halide perovskite has also increased.The CH₃NH₃PbBr₃lead halide perovskite obtained by remolding is not only very high in crystal quality,but also stable,and does not decompose even if it is placed in the air for 454 days.This one-dimensional core-shell heterojunction microwire with high stability has laid a solid foundation for the application of lead halide perovskite photodetectors.3.Resaech on the performance of one-dimensional（CH₃）₂C=NHCH₃PbBr₃/CH₃NH₃PbBr₃core-shell heterojunction photodetector.Drop silver paste on both ends of a single（CH₃）₂C=NHCH₃PbBr₃lead halide perovskite microwire as the electrodes of the photodetector.The distance between the electrodes is as close as possible without forming a short circuit.Then expose it to the air,and the surface layer of the area where the（CH₃）₂C=NHCH₃PbBr₃ lead halide perovskite microwire is not covered by the silver paste will be converted into CH₃NH₃PbBr₃ lead halide perovskite,thus obtaining the interdigital（CH₃）₂C=NHCH₃PbBr₃/CH₃NH₃PbBr₃core-shell heterojunction microwire photodetector.The study found that benefiting from the existence of the heterojunction structure can inhibit the recombination of carriers and increase the carrier lifetime,and facilitate the separation of carriers.Under 460nm light excitation,the（CH₃）₂C=NHCH₃PbBr₃/CH₃NH₃PbBr₃ core-shell heterojunction photodetector has a large responsivity of 66.8 mA W^-1 and a high response speed（2.8ms/0.8ms）.