Research On High-Performance Photodetectors Of Lead-and Bismuth-Based Halide Perovskite

In the past few years,perovskite has attracted much attention in the field of photoelectric conversion devices.At the same time,because of the characteristics of perovskite with adjustable band gap,high carrier mobility and solution synthesis,it is very suitable for application in the field of photodetectors.Therefore,how to better combine with photodetectors has become a new research focus.This thesis mainly focuses on the preparation process,device design and imaging application of lead based（Cs Pb Br₃,CH₃NH₃Pb I₃）and bismuth based(Cs Bi₃I₁₀)perovskite photodetectors.The main work includes the following contents:1.In order to broaden the response wavelength of quantum dots（QDs）photodetector and improve the response speed,Cs Pb Br₃ QDs and Pb S QDs composite materials are studied in the thesis.Because of the high carrier mobility of Cs Pb Br₃ QDs and the narrow band gap of Pb S QDs,the photodetector can work in visible and infrared with fast response speed even at zero bias.In addition,in order to avoid the poor quality of all inorganic brominated perovskite film prepared by solution due to the low solubility of Cs Br,the one-step thermal evaporation method for preparing Cs Pb₂Br₅-Cs Pb Br₃ perovskite composite film is studied in this thesis,and its photoelectric properties are characterized.Meanwhile,the grain size increases after annealing.Finally,the response speed and responsivity of the composite films to 405 nm light illumination at 5 V bias are studied.2.In order to improve the film quality of CH₃NH₃Pb I₃ and the responsivity of photodetector,a new method of preparing CH₃NH₃Pb I₃ film by using excessive PMMA as the anti-solvent is proposed.In addition,a post-treatment process is proposed to remove excessive PMMA to avoid the strong insulation.In order to realize the array imaging application of perovskite photodiode,this thesis also studies the image sensor after the combination of CH₃NH₃Pb I₃ photodiode and rectifier diode.The device can realize the off state under zero bias without designing an electrical switch,so it avoids the imaging blur caused by crosstalk.Finally,the photoelectric performance and imaging of the device are tested and analyzed.3.In order to solve the instability and toxicity of lead-based perovskite and improve performance of lead-free perovskite photodetector,a Cs Bi₃I₁₀/PCBM bulk heterojunction photodetector with dual working mode is proposed.The device can work normally under forward and reverse bias.At reverse bias,it has a fast response speed and can be used in optical communication.At forward bias,it has a high responsivity and specific detectivity and can be used in weak light detection.