First Principle Study Of Inorganic Perovskite CsSnI_xBr_3-x

In recent years,the deterioration of the global environment problems forced people to accelerate the research on new energy.In many kinds of new energy,solar energy has been favored by scientists for its advantages of environmental protection,efficient and can be applied to a large area.For many years,scientists have been looking for an efficient,stable and inexpensive solar power generation material,perovskite solar cells came into being.The paper studied CsSnI₃ from two aspects:preparation and simulation doping.The most widely used process for preparing CsSnI₃ film is to obtain powder by solid phase reaction,Then dissolved in organic solvent,spin coating film.The CsSnI₃film prepared by this method has poor stability and uneven film thickness,and its electrical and optical properties are weakened to some extent due to the poor stability.The paper prepared CsSnI3 thin films by vacuum evaporation,The CsI and SnI2 powders were evaporated and deposited on the glass substrate successively.The two kinds of films were reacted to form CsSnI3 perovskite films by thermal insulation.The effect of different amounts of drugs and evaporation order of drugs on the properties of the films was studied..It is found that the different evaporation order will affect the orientation of the film,thus affecting the quality of the CsSnI₃ film;the dosage and evaporation rate of the film will also affect its performance.The simulation part calculated the perovskite absorption layer CsSnIxBr3-x by VASP package with First principles.The three phase of the initial CsSnI₃ cell was optimized by optimization with pot-GGA pseudopotential,then relax the structure by doping halogen to calculate the total energy,and selects a more stable structure system for electronic structure calculations.After analyzing the calculated band and density of States.It is found that the substitution of atoms with different symmetry in different phase perovskite will have different effects on the band structure and band gap.The results show that the band gaps of CsSnI₃ cubic,tetragonal and orthorhombic phases are 0.41 eV,0.55 eV and 0.58 eV,which are in good agreement with the literature.The cubic phase's band gap increase steadily after doping Br,tetragonal and orthorhombic phase due to the existence of different halogen atom symmetry,so the band gap rise volatility during doping.CsSnI₃ the top of the valence band dominants by I 5p orbital and Sn 5S orbital,while his bottom of the conduction band dominants by I atoms of the 5P orbital and Sn 5p orbital,which shows that when the incident light onto the surface of CsSn I₃,electrons on Sn 5S and I 5p orbital are excited to transition to Sn 5p orbital.The result agrees with experimental facts and has good reliability.