Design and Simulation of Thermally Stable Lead-Free BaHfSe3 Perovskite Solar Cells: Role of Interface Barrier Height and Temperature

Lead-free chalcogenide perovskites are emerging as promising alternatives to hybrid halide perovskites due to their superior thermal stability, non-toxicity, and strong optical absorption. In this study, the photovoltaic performance of single-junction BaHfSe3-based perovskite solar cells (PSCs) with the TCO/TiO2/BaHfSe3/Cu2O/Au configuration is systematically investigated using SCAPS-1D simulations. Device optimization identifies TiO2 and Cu2O as suitable ETL and HTL materials, respectively. The optimized structure—TCO/TiO2 (50 nm)/BaHfSe3 (500 nm)/Cu2O (100 nm)/Au—achieves a power conversion efficiency (PCE) of 24.47% under standard conditions. Simulation results reveal that device efficiency is influenced by absorber thickness and trap density. A detailed temperature-dependent study highlights that photovoltaic parameter efficiency is governed by the barrier alignment at the TCO/ETL interface. For lower TCO (Transparent Conducting Oxide) work functions (3.97–4.07 eV), PCE decreases monotonically with temperature, attributed to the increase in reverse saturation current resulting from a higher intrinsic carrier concentration. By contrast, higher TCO work functions (4.47–4.8 eV) yield an initial increase in efficiency with temperature, driven by reduced barrier height and favorable Fermi level shifts before efficiency declines at further elevated temperatures. These insights underscore the promise of BaHfSe3 as a lead-free, environmentally robust perovskite absorber for next-generation PSCs, and highlight the critical importance of interface engineering for achieving optimal thermal and operational performance.