First-principles Calculation And Analysis Of CsPbX₃(X=Cl,Br,I) And Its Vacancy Defects

In recent years,the all-inorganic lead halide perovskite CsPbX₃(X=Cl,Br,I)have attracted much attention due to its excellent characteristics such as adjustable response wavelength,high electron mobility,and quantum yield.The materials have shown good application prospects in a variety of optoelectronic devices.The geometric structure,elec-tronic properties and defect properties of materials greatly affect the performance of op-toelectronic devices based on perovskites.So it's necessary to calculate and analyze the geometric structure,electronic properties and defect properties to provide theoretical sup-port for the promotion of the application based on all-inorganic perovskites.In this paper,we systematically conduct first-principles calculations and analyses on the crystal structure,electronic properties and defect properties of all-inorganic perovskite CsPbX₃in order to understand their structure and electronic properties more comprehensively.In this paper,the density functional theory-based quantum mechanics program CASTEP in the materials calculation software Materials Studio is used for theoretical calculations.Firstly,different functionals are used to optimize the geometry of all-inorganic perovskite CsPbCl₃,CsPbBr₃and CsPbI₃.Compare and analyze the all-inorganic perovskites with different halogen by calculating the electronic properties such as band structure,density of states,charge population and electron density difference.Based on the study of intrin-sic perovskite CsPbX₃,the geometric structure,formation energy and electronic properties of CsPbX₃with Cs,Pb and X(X=Cl,Br,I)vacancy defects are calculated to analyze the influence of different vacancy defects on electronic properties and structural stability of all-inorganic perovskites with different halogen elements.Based on the study of CsPbX₃,the structure and electronic properties of CsPbI₃with cubic,tetragonal and orthogonal phase are calculated and analyzed.Because of the heavy metal Pb atoms,the spin coupling is also considered when calculate the band structure.The results of all-inorganic perovskites show that the band gap of CsPbI₃is the nar-rowest,and CsPbX₃are direct band gap semiconductors.With the change from Cl to I,the ionic nature of the Cs-halogen anions gradually increases,and the covalent nature of the Pb-halogen anions gradually weakens.It's found that Cs vacancy defects and Pb vacancy defects make the material a p-type semiconductor,and I vacancy defects make the material a n-type semiconductor through the calculation and analysis of vacancy defects.The struc-ture of CsPbI₃is more stable bacause it has the lowest formation energy.The orthogonal phase of CsPbI₃is more stable,and the cubic phase has better electronic properties.In short,the research has enabled a more comprehensive understanding of the structure and electronic properties of the all-inorganic perovskite CsPbX₃(X=Cl,Br,I),and provided a theoretical basis for the further development of CsPbX₃in optoelectronic devices.