Effect of metal (Cr, Sr, Ag, Cu) doping on the performance of lead-free RbSnI3 based perovskite solar cells: A theoretical approach

Abstract Perovskite solar cells based on lead have witnessed unprecedented growth over the past decade, achieving an impressive power conversion efficiency (PCE) of 26.1%. However, lead toxicity remains a concern for commercialization. In order to resolve the matter, scientists have been investigating alternative materials; in this context, rubidium-based lead-free perovskites like RbSnI 3 may be a promising alternative because it has a high optical conductivity and absorption coefficient. Density Functional Theory (DFT)-based first-principles studies are used in this work to examine the effect of metal doping (specifically Cr, Sr, Ag, and Cu) on the optoelectronic and structural characteristics of orthorhombic RbSnI 3 perovskite. In addition, we conducted a comprehensive study to investigate the impact of metal doping on the formation energy, structural stability, and HOMO–LUMO energy levels of RbSnI 3 perovskite. Introducing transition metal cations (Cr 2+ , Ag + , and Cu + ) at the Rb site results in a flat band in the conduction band region, transforming the RbSnI 3 ’s indirect band gap into a direct one and significantly affecting the optoelectronic properties. The DFT results are then integrated into the Solar Cell Capacitance Simulator (SCAPS-1D) to estimate the effectiveness of the modeled device. The Cu-doped RbSnI 3 device exhibits the highest PCE of 20.2%. Furthermore, Ag and Cu doping in RbSnI 3 increases bond length, which reduces exciton binding energy and helps with charge carrier generation.