Optimization of CsSnBr₃-based lead-free perovskite solar cells by numerical simulation using SCAPS-1D

The remarkable optoelectronic properties, tunable band gaps, and cost-effective solution-processable fabrication of perovskite solar cells (PSCs) have garnered a lot of attention. However, during post-use disposal, the presence of lead (Pb) in high-performing perovskites poses major health and environmental risks. The demand for Pb-free substitutes is prompted by the ecological concerns associated with even trace Pb leaking. Among these, cesium tin bromide (CsSnBr₃) has shown promise as a non-toxic alternative with advantageous electrical properties. A thorough computational optimization of CsSnBr₃-based PSCs using solar cell capacitance simulator-one dimension, which resolves coupled Poisson, carrier transport, and continuity equations, is presented in this work. ITO/phenyl-C61-butyric acid methyl ester/CsSnBr₃/Cu:NiO X /Ni demonstrated the best performance and was chosen for further analysis after investigating a variety of ETL/CsSnBr₃/HTL configurations. Absorber thickness was optimized to achieve the optimal conversion efficiency out of the cell. Statistical distribution of photovoltaic metrics to study the sensitivity of absorber mobility was conducted. The photovoltaic response of the cell was assessed by varying parameters, including absorber crystallinity and interfacial defect density. The recombination resistance (R rec ) was examined in the frequency domain using Electrochemical Impedance Spectroscopy, which complemented the time-domain results. Additionally examined were the effects of series resistance (R S ), shunt resistance (R Sh ), operating temperature, and back contact metal on the cell performance. An 800 nm thick CsSnBr 3 with an acceptor doping of 10 17 cm −3 and defect density of 10 14 cm −3 exhibited a theoretical maximum efficiency of 21.40%, which was attained by the improved device architecture, indicating the high potential of CsSnBr 3 as a practical Pb-free photoactive layer. These results offer a theoretical foundation to guide future experimental efforts for the development of sustainable, high-performance Pb-free PSCs and provide an insightful strategy for device architectural design.