Exploring the Optoelectronic Properties and Solar Cell Performance of Cs2SnI6−xBrx Lead-Free Double Perovskites: Combined DFT and SCAPS Simulation

Abstract

This paper presents detailed results regarding the physical behavior of Cs2SnI6−xBrx alloys for their potential use in photovoltaic applications. Numerical computations based on density functional theory (DFT) revealed that Br substitution at I sites significantly influenced the electronic structure of Cs2SnI6, resulting in an increase in bandgap values from 1.33 eV to 2.24 eV. Additionally, we analyzed the optical properties, including the absorption coefficient, which exhibited high values in the visible light region, highlighting the material’s excellent light-trapping abilities. Moreover, Cs2SnI6−xBrx compounds were employed as absorber materials in an fluorine-doped tin oxide (FTO) TiO2/Cs2SnI6/P3HT/Ag perovskite solar cell (PSC) to investigate its performance. The simulation process consisted of two interconnected steps: (i) the DFT calculations to derive the material properties and (ii) the SCAPS–1D (one-dimensional (1D) solar cell capacity simulator) simulation to model device performance. To ensure reliability, the SCAPS–1D simulation was calibrated against experimental data. Following this, Cs2SnI6−xBrx compound with various ratios of Br content, ranging from 0 to 6, was investigated to propose an efficient solar cell design. Furthermore, the cell structure was optimized, resulting in a development in the power conversion efficiency (PCE) from 0.47% to 3.07%.