Advancing Solar Energy with Cs2TlAsI6 Double Halide Perovskite: A Simulation-Driven Approach for High-Efficiency Solar Cell

Perovskite solar cells (PSCs) are emerging as promising candidates for next-generation photovoltaics due to their remarkable optoelectronic properties. In this study, SCAPS-1D(Solar cell Capacitance Simulator) simulations are employed to evaluate the photovoltaic performance of a lead-free double perovskite, Cs₂TlAsI₆, as an absorber material. A total of 54 device architectures are systematically explored by combining six different electron transport layers (ETLs: Ws₂, TiO₂, C₆₀, PCBM, IGTO, and LBSO) with nine-hole transport layers (HTLs: CBTS, Cu₂O, CuI, CuSCN, P3HT, PEDOT: PSS, PTAA, GaAs, and CdTe), using Ni as the back contact. The ITO/Ws₂/Cs₂TlAsI₆/Cu₂O/Ni configuration achieves the highest power conversion efficiency (PCE) of 26.92%. Further optimization examines the influence of absorber thickness, ETL hthickness, and defect densities on performance. Detailed analyses include band alignment (VBO/CBO), interface defects, carrier dynamics, quantum efficiency, capacitance profiles, Mott–Schottky behavior, and impedance spectra. Additionally, the effects of series and shunt resistance, temperature, and back contact selection are investigated. Structural stability of Cs₂TlAsI₆ is confirmed via tolerance factor analysis, including Goldschmidt's and a newly proposed parameter. This simulation-driven architectural optimization offers new insights into the potential of Cs₂TlAsI₆-based PSCs and provides practical design strategies for high-efficiency, lead-free photovoltaic devices.