Advancing photovoltaics with Cs₂NaInI₆-based perovskites: a simulation study on ETL optimization

Developing reliable, energy-efficient, and eco-friendly photovoltaic materials is crucial for advancing next-generation solar technologies. Among lead-free options, double perovskites such as Cs₂NaInI₆ show strong potential due to their direct bandgap (∼1.6 eV), excellent light absorption, high carrier mobility, and environmental durability. The efficiency of Cs₂NaInI₆-based perovskite solar cells (PSCs), however, is strongly influenced by the electron transport layer (ETL). In this work, Solar Cell Capacitance Simulator in One Dimension (SCAPS-1D) simulations were employed to analyze ITO/ETL/Cs₂NaInI₆/Au structures using WS₂, SnS₂, In₂S₃, and IGZO as ETLs. Critical factors-absorber thickness, defect density, doping levels, interface traps, and temperature-were systematically tuned to assess their effects on power conversion efficiency (PCE), open-circuit voltage (V _OC), short-circuit current density (J _SC), and fill factor (FF). Among the tested ETLs, WS₂ delivered the best performance with a PCE of 22.63%, V _OC of 1.189 V, J _SC of 21.406 mA cm^-2, and FF of 88.92%, attributed to favorable band alignment, high mobility, and reduced recombination. Additionally, Cs₂NaInI₆ demonstrated promising thermal and defect stability, emphasizing its viability for real-world applications. Overall, this study underscores the critical role of ETL engineering and provides a simulation-guided approach for designing efficient lead-free perovskite solar cells (PSCs).