| Solar energy is a renewable and clean energy source that can solve global warming and greenhouse gas problems caused by fossil fuels.In nine years,the photoelectric conversion efficiency of perovskite solar cells has increased rapidly to 23.2%.In order to make the best use of sunlight,the band gap engineering of perovskite film was explored.One way to further enhance the use of sunlight is to prepare a perovskite film with a gradient band gap.In this paper,a gradient band gap hybrid halide-perovskite film was prepared by evaporating different mass ratios of MAPbBr3 and MAPbI3 single crystals;perovskite solar cells were prepared by single source thermal evaporation technique and one-step spin coating.The main research contents are as follows:(1)A large number of MAPbBr3 and MAPbI3 single crystal samples were prepared by inversion crystallization(ITC).Seven MAPbBr3/MAPbl3 mixed perovskite films were prepared by thermal evaporation technique of perovskite single crystal.The mass ratios of MAPbBr3 and MAPbI3 were 6:0,5:1,4:2,3:3,2:4,1:5 and 0:6,and the total thickness of each sample film was about 400 nm.The band gap of the MAPbBr3/MAPbI3 mixed films were calculated to gradually change with the mass ratio of MAPbI3 and MAPbBr3 single crystals,and the band gap varied from 1.43 eV(MAPbI3)to 2.28 eV(MAPbBr3).This study developed a method for preparing a gradient band gap mixed halide perovskite film that can be applied to the photovoltaic field,such as tandem solar cells.(2)Perovskite films were prepared by thermal evaporating MAPbI3 perovskite single crystals of different molar ratios of organic portion(MAI)to inorganic portion(PbI2),perovskite films with different thicknesses prepared by thermal evaporating different masses of MAPbI3 perovskite single crystals.The structure of perovskite solar cells devices were ITO/SnO2/MAPbI3/Spiro_OMeTAD/Ag prepared under different conditions.The photoelectric conversion efficiency was measured and the optimal conditions for the preparation of perovskite films and perovskite solar cells were investigated:the perovskite film obtained by single-source thermal evaporating 0.6 g MAI:PbI2=1.5:1 perovskite single crystal.The preparation of perovskite solar cells has the highest photoelectric conversion efficiency of 4.56%.(3)MAPbl3 perovskite films were prepared by single-source thermal evaporation technique and one-step spincoating.The solar cells were prepared by the two films.The photoelectric conversion efficiency of the latter was found to be higher than the former,and the conversion efficiency was 14.42%.Comparing the two films,the crystallinity of the MAPbI3 film has a significant influence on the photoelectric conversion efficiency,it is found that increasing the crystallization of the perovskite film can improve the photoelectric conversion efficiency.This provides guidance for the future research of highly efficient perovskite solar cells. |
