Preparation And Properties Of New Perovskite Semiconductor CsSnBr₃

In order to solve the major energy problems encountered in the process of human development,such as:energy shortage,unreasonable energy structure and environment pollution,searching for renewable energy become a World-class research hotspot.Inexhaustible solar energy is one of the most promising source of renewable energy.Based on semiconductor photovoltaic effects,solar cells could convert light energy into electrical energy directly.However,the high energy consumption and complicated manufacturing processes of commercial silicon solar cells hinder their further application.Halide perovskites?ABX₃?have attracted large research attention for its advantage on inexpensive starting materials,no complicated preparation technology,and so on.In the past nine years,the efficiency of single-junction perovskite solar cells has increased from 3.8%to 23.3%,as good as commercial silicon solar cells.However,the Pb element used in the most researched perovskite solar cells is not environmentally friendly,and tin halide perovskite materials are one of potential alternative materials.Among various tin halide perovskites,all inorganic CsSnBr₃ has excellent physicochemical properties.The following studies focused on CsSnBr₃ and expected to provide guidance to improve CsSnBr₃ solar cells efficiency:?1?SnBr₂ was purified as a raw material for preparing a CsSnBr₃ powders precursor.After optimizing the growth process of CsSnBr₃ single crystals,we got high quality large-size single crystals.We find surfactant additives affect the crystals morphology.More specifically,a certain amount of cetyl trimethyl ammonium bromide?CTAB?could expose the?110?face of CsSnBr₃ crystal.?2?The exciton binding energy and dielectric constant of CsSnBr₃ and MASnBr₃were experimentally measured.It is found that CsSnBr₃ has a relative high dielectric constant?and low binding energy E_b because of a compact SnBr₃^-framework structure not A site ions.Theoretical analysis agrees well with experiment results.The gains come from the band gap?E_g?,optical dielectric constant(?_Eg?)and the effective mass of the charge carriers??₀?build up to the E_b of CsSnBr₃ lower than the room temperature thermal energy(K_BT_rt),indicating that the CsSnBr₃ semiconductor has free photo generated carriers.In addition,CsSnBr₃ have good stabilities against heat and air.CsSnBr₃ has a band gap of 1.9 eV and is suitable for forming tandem solar cells with Si.This work has been published on Angew.Chem.Int.Ed..?3?The spectral characteristics and surface degradation mechanism of CsSnBr₃crystals were discussed.The schottky photodetector based on CsSnBr₃ crystal was prepared and the hall effect of CsSnBr₃ crystal was studied.The carrier lifetime and carrier diffusion length of CsSnBr₃ crystal is calculated and measured experimentally.?4?We calculated and measured the E_vac^VBM of the CsSnBr₃ crystal.The calculated value match the experimental value very well.We found when using TQB as a organic electronic transport material and Au as a hole transport material for CsSnBr₃,according to its energy level,the carriers collection efficiency of CsSnBr₃photodetector could be improved.This part work is trying to explain the importance of energy level match between perovskite and transport materials,and what we found point out the direction for improving the PCE of CsSnBr₃ solar cell.This work has been accepted by the journal J.Phys.Chem.Lett..