A First-Principle Study On The Effect Of A-site Doping And Substituting On Structure Of Perovskite Materials

Due to its simple production process,low cost and high photoelectric conversion efficiency,perovskite solar cells are considered as one of the most promising new energy batteries to replace traditional fossil energy resources.As the core part of perovskite solar cells,It has been the goal of the researchers,how to improve the composition of perovskite absorbing materials and enhance the stability of materials.It hinders the design and decelopment of new perovskite materials because of the complex composition and lattice structure of AnBXm perovskite materials or seriously lacking systematic theoretical guidance of the influence of doping and substitution of different A sites on the materials.In this paper,the doping and replacement of A-site cations is doped or replaced by ab initio molecular dynamics and first-principles calculations,and a long-term and large-scale molecular dynamics simulation of the new perovskite materials was carried out.The geometrical structure and energy band change of perovskite materials in the process of dynamic simulation are compared and analyzed systematically.The theoretical calculation data are in good agreement with the existing experimental results.In this paper,the doping of NH4+ and FA+ cations and the replacement of five cations of NH4+,MA+,FA+,(CH3)4N+ and Ni(C10H8N2)32+ were mainly studied.It can be seen that when 0<n<1,Some Pb-I bonds of the Pnma type 2D perovskite material rupture and recombine with other Pb or I ions resulting in a mixed-dimensional perovskite material from the(NH4)1-n(FA)nPbI3(n=0,0.625,0.75,0.875,1)material obtained by doping.The bandgap will gradually decrease with the formation of mixed-dimensional perovskite material and close to the best bandgap of 1.4eV.In addition,the substitutional simulation of five A-site cations of NH4+,MA+,FA+,(CH3)4N+ and Ni(C10H8N2)32+ on the basis of AnBXm perovskite materials shows that the stability of the perovskite material is related to the cation size and the number of hydrogen bonds with the halogen ions directly:The larger size of the cation or the more N-H groups that can form hydrogen bonds with the halogen ions directly,the smaller degree of distortion of the crystal structure and the less crystal defects,Therefore the stability of the perovskite material is enhanced.This work is of great significance to select and design a new type of perovskite absorbing materials reasonably.Therefore It can improve the photovoltaic properties and stability of PSCs.