Engineering efficient RbGeCl3 perovskite solar cells: A simulation-driven computational approach to performance optimization

The development of lead-free perovskite solar cells (PSCs) is critical for advancing environmentally sustainable photovoltaic technologies. This study systematically evaluates the photovoltaic potential of RbGeCl 3 as a lead-free absorber using SCAPS-1D simulations. Unlike studies, this work goes beyond limited configurations or single-layer studies by delivering multi-parameter optimization and comparative ETL engineering of RbGeCl 3 PSCs for high-performance lead-free devices. An initial screening of 48 device configurations with varied electron transport layers (ETLs) and hole transport layers (HTLs) identified four promising architectures of the form FTO/ETL/RbGeCl 3 /MoS 2 /Pt employing SnS 2 , WS 2 , WO 3 , and CdS as ETLs. Among these, the SnS 2 -based device delivered the highest performance, achieving a PCE of 19.29%, V OC of 0.692 V, J SC of 34.28 mA cm − 2 , and FF of 81.19% at an optimized absorber thickness of 0.5 μm and defect density of 10 15 cm − 3 . Comprehensive optimization- including absorber and ETL thicknesses, bulk and interfacial defect densities, temperature effects, and series/shunt resistances revealed strong structure-dependent performance trends. All devices exhibited excellent photoresponse, with EQE values exceeding 90% across 400–800 nm, confirming efficient photon absorption and carrier extraction. and alignment (VBO/CBO), Mott-Schottky and recombination analyses revealed favorable energy-level alignment and a strong built-in electric field across the optimized architectures, leading to reduced recombination losses and enhanced charge transport. Impedance analyses further verified the operational robustness of the optimized structures. Collectively, the findings of this study identify RbGeCl 3 as a promising lead-free absorber with strong optical response, suitable band energetics, and ETL compatibility, providing design insights for efficient and stable environmentally benign PSCs.