Study On Crystal Quality Regulation And Construction Of High-Performance Perovskite Photodetectors

As an important member of advanced intelligent photoelectric systems,photodetectors have been widely used in many fields,such as optical communication,high-resolution imaging,and health monitoring.For the past few years,perovskite materials have been widely studied owing to their characteristics of tunable bandgap and solution preparation method,and they have become the best choice for developing photodetectors.However,the intrinsic defect of perovskite increases the dark current of the photodetectors,which reduces their detectivity and stability.In addition,as a multilayer device,the energy level mismatch in photodetectors has seriously impacted the carrier transmission,which has limited the further improvement of the response speed.This thesis is based on the preparation and crystal quality regulation of perovskite.These studies focus on the following aspects:surface modulation strategy was used to improve the energy level mismatch;grain boundary crosslinking strategy was used to passivate defects;and interface repair strategy was used to improve the interface transmission capacity of carriers.Through the above strategies,the detectivity,response speed,and stability of perovskite photodetectors could be further improved.Furthermore,the optical communication system was designed to achieve audio transmission.The perovskite materials were prepared at first.CsPbBr₂I quantum dots were synthesized by the hydrothermal method,and the surface modulation strategy of potassium trifluoroacetate（KTFA）was used to improve the uniformity of quantum dots.The two-step spin coating method was used to prepare FAPbI₃ films,and the N,N’-methylene diacrylamide（MBA）crosslinking strategy was used to increase the crystal size and reduce roughness.Based on the two-step dynamic method,the preparation process of perovskite was optimized by the interface repair strategy of 1,3-diiodo-5,5-dimethylhyne（DIH）.This strategy reduced the surface defects of perovskite films.The KTFA surface modulation strategy of CsPbBr₂I quantum dots was developed to improve crystal quality and photoelectric properties.The surface modulation strategy of KTFA on defect passivation and energy level regulation was studied.Thanks to the passivated defects,the increased built-in potential,and the enhanced carrier transport capability,the photodetectors achieved a responsivity of 0.375 A/W,and a detectivity of 1.1210¹³ Jones.In addition,the optimized photodetectors exhibited a wide applicable temperature range from18℃ to 80℃.The MBA crosslinking strategy was developed to prepare high-quality FAPbI₃ films.The crosslinking reaction of MBA monomers were studied.The results showed that the MBA crosslinking strategy can delay crystallization kinetics and promote the growth of perovskite in vertical orientation.In addition,the tensile strain of the films was released by 48%,and the lattice distortion had been alleviated.The strategy effectively passivated the defects of perovskite and significantly inhibited the dark current of photodetectors.Thanks to the suppressed dark current of 2.110^-12 A,the flexible and self-powered photodetectors achieved a detectivity of 6.610¹³ Jones,a linear dynamic range of 155 dB,and a responsivity of 0.61 A/W.The crosslinking photodetectors maintained excellent weak light detection ability even after 1000 bending cycles.The dynamic two-step method was used to prepare FAPbI₃ films.The DIH interface repair strategy was adopted to inhibit the iodine vacancy defects and improve the crystal quality.The effects of the interface repair strategy on carrier behavior and recombination dynamics were studied.Thanks to the enhanced carrier transport capability and improved energy level alignment,the constructed photodetectors demonstrated an improved response speed of 0.105 ms,a detectivity of 3.510¹³ Jones,and a responsivity of 0.66 A/W.The repaired photodetectors exhibited enhanced light stability.In addition,the photodetectors also demonstrated the air stability for 4 months.Moreover,the photodetectors were used as the receiving terminal of the visible optical communication（VLC）system,and the VLC system was built for audio transmission functions.