Study On Electronic Structure And Optical Properties Of CsPbBr₃ Heterojunction

In recent years,organic-inorganic hybrid perovskite batteries have developed rapidly,and their photoelectric conversion efficiency has been increased from 3.8%to 25.2%,however the stability is one of the bottlenecks preventing their commercialization.The all-inorganic perovskite material CsPbBr₃ has become one of the hotspots in the field of perovskite solar cells due to its good thermal stability.However,CsPbBr₃ perovskite has low photoelectric conversion efficiency due to its high interface charge recombination rate and weak light absorption.Therefore,the effective separation of interface carriers and the enhancement of the absorption spectrum are the keys to achieving a highly efficient CsPbBr₃ perovskite solar cell.In this paper,by designing and constructing CsPbBr₃-based heterostructures,the band structure,state density,differential charge density,Mulliken charge distribution,band order arrangement,absorption spectrum,photoconductivity,etc.at the interface of the heterostructure are simulated and calculated to reveal the differences from the perspective of electronic structure.The inherent characteristics of the charge transfer mechanism and interaction at the mass-junction interface provide the micro-mechanism for reducing the photogenerated carrier recombination rate and enhancing the light absorption,and provide theoretical guidance for the experimental preparation of high-performance CsPbBr₃-based heterostructured perovskite solar cells.The main research work and conclusions of the paper are as follows:?1?The CsPbBr₃/graphene heterostructure was designed and constructed.The optical and electrical properties of the CsPbBr₃/graphene heterostructure were studied by a combination of experiments and theories.The results show that the built-in electric field at the interface of the CsPbBr₃/graphene heterostructure can effectively inhibit the recombination of photo-generated carriers.The electrons in the photo-generated carriers flow from the CsPbBr₃ layer to the graphene electron transport layer,photo-generated carriers are effectively separated.Secondly,the smaller effective carrier mass in the CsPbBr₃/graphene heterojunction helps to improve the carrier mobility,thereby further accelerating the carrier separation at the interface.Thirdly,in the CsPbBr₃/graphene heterostructure,the photoelectric properties of thePbBr₂/graphene interface are better than the Cs Br/graphene interface.This is due to the stronger self-built electric field at thePbBr₂/absorption.Finally,PL spectra,UV-visible absorption spectra,electrochemical impedance test spectra,and photocurrent test results of CsPbBr₃/graphene heterojunction samples further confirmed the reliability of the theoretical calculation results.?2?The CsPbBr₃/XS₂?X=Mo or W?heterostructure was designed and constructed.The interface charge transfer mechanism and optical characteristics of the CsPbBr₃/XS₂heterostructure were studied.The energy band structure,state density and differential charge density calculation results show that the CsPbBr₃/XS₂ heterojunction is a type II heterojunction,which is conducive to the spatial separation of photo-generated carriers.Secondly,the self-built electric field at the CsPbBr₃/XS₂ heterojunction interface can further accelerate the effective separation of photo-generated carriers;comparing the differential charge density and band order arrangement of CsPbBr₃/Mo S₂ and CsPbBr₃/WS₂ heterojunctions,the charge transport performance of CsPbBr₃/Mo S₂ is better than CsPbBr₃/WS₂.This is due to the large band shift at the interface of the CsPbBr₃/Mo S₂heterostructure.Third,the charge transfer ability of thePbBr₂/Mo S₂ interface is better than that of the Cs Br/Mo S₂ interface,and the charge transfer ability of thePbBr₂/WS₂ interface is better than that of the Cs Br/WS₂ interface;the light absorption and photoconductivity of the CsPbBr₃/XS₂ heterostructure are significantly enhanced.