Multiscale Investigation of Lead-Free Ce-Based Perovskite: From DFT-Derived Optoelectronic Properties to Photovoltaic and Photocatalytic Performance

This study presents a comprehensive simulation-based investigation of lead-free Rb 2 CeCl 6 perovskite solar cells (PSCs) using the DFT and SCAPS-1D framework. Structural analysis confirms the cubic stability of Rb 2 CeCl 6 with a suitable tolerance factor and a direct bandgap of 1.748 eV, making it highly effective for visible-light absorption. Optical simulations reveal high absorption coefficients (>59,000 cm -1 ) and a favourable dielectric response, indicating strong photon-harvesting and exciton dissociation capabilities. Mechanical analysis demonstrates elastic stability, ductility, and low anisotropy, supporting its suitability for thin-film device fabrication. Photocatalytic assessment based on band edge alignment reveals that the conduction band minimum (–0.414 eV) is sufficiently negative to drive hydrogen evolution and multiple CO 2 reduction pathways, while the valence band maximum (0.838 eV) supports oxidation reactions, confirming the material’s thermodynamic feasibility for solar-driven photocatalysis. Energy band alignment studies identify WS 2 and TiO 2 as optimal electron transport layers (ETLs), offering minimal interfacial recombination and improved charge extraction. Parametric analysis of absorber thickness, ETL thickness, doping concentration, and defect density reveals that optimal values significantly enhance PV performance, with a peak power conversion efficiency (PCE) of 20.94% achieved using WS 2 as the ETL. The study further explores the impact of temperature, series and shunt resistance, and generation–recombination dynamics, highlighting that device performance is maximized around 300 K with low recombination and minimal parasitic losses. Overall, the combined DFT and device-level results demonstrate that Rb 2 CeCl 6 is a promising eco-friendly material for next-generation energy applications, offering strong potential for both high-efficiency PV devices and solar-driven photocatalytic processes.