Numerical insights into CsSnBr3 perovskite solar cells: Evaluating organic charge transport layers using DFT, SCAPS-1D, and wxAMPS simulations

Abstract

Perovskite solar cells mark a breakthrough in photovoltaic technology, attributed to their excellent optoelectronic characteristics, adjustable band gaps, and simplistic fabrication processes. Cesium-based perovskites have been the focus of research into lead-free substitutes, with CsSnBr₃ emerging as a noteworthy contender for application as an absorber layer in solar cells. This study employed the Cambridge Serial Total Energy Package (CASTEP) to conduct density functional theory (DFT) calculations to examine the optical, electronic, and structural properties of cubic CsSnBr₃. In CASTEP, the GGA-PBE approach was employed to determine the band gap (E_g) of CsSnBr₃, which was determined to be 0.614 eV. Upon analyzing the electronic charge density map, it was determined that the Br-4d orbital is the primary factor influencing the density of states (DOS), with charge accumulation predominantly around the Br atom. Different CsSnBr₃-based device structures were modeled in SCAPS-1D to investigate photovoltaic efficiency, while the optical characteristics were investigated to evaluate the material's optical response. Configurations included PFN:Br as the ETL and evaluated four organic HTLs: GO, PTAA, PEDOT:PSS, and P3HT, with the objective of identifying optimal ETL/CsSnBr₃/HTL combinations. The simulation results indicated that the device architecture ITO/PFN:Br/CsSnBr₃/P3HT/Ni attained the highest photoconversion efficiency of 24.01% among the configurations evaluated. The research evaluated the impact of varying absorber, ETL, and HTL thicknesses; doping levels; interface defects; series resistance; shunt resistance; and operating temperature on device performance. Performance indicators were assessed using current density-voltage and quantum efficiency analysis. The outcomes of SCAPS-1D simulations were corroborated by comparing them with wxAMPS results.