Electron extraction layer-driven performance enhancement in CaHfSe₃ photovoltaics

Traditional solar cells - including those based on silicon or lead-halide perovskites - have a number of significant disadvantages, including long-term instability, costs, and toxicity. We demonstrate the suitability of CaHfSe₃ as a promising next-generation lead-free thermally stable absorber material. We performed a comprehensive numerical simulation study using SCAPS-1D to consider several device topologies of the type FTO/TiO₂ AZnO, WS₂/CaHfSe₃/MoO₃/Au, and to investigate the different features of a system based on CaHfSe₃. We conducted a full parametric study of the impacts of absorber thickness, defect density, acceptor doping and concentration, as well as carrier concentrations in the electron and hole transport layers. In addition, through experimentation we considered the operational characteristics of carrier generation-recombination methods, temperature and back contact effect current-voltage <i>I</i>-<i>V</i> characteristics, quantum efficiency, and the influence of series and shunt resistance. This allowed us to determine the optimized configuration. The top-performing structure, FTO/TiO₂/CaHfSe₃/MoO₃/Au, had an outstanding PCE of 32.39%, <i>V</i> _OC = 1.52 V, <i>J</i> _SC = 23.17 mA cm^-2, and FF = 91.41%. This research offers both fundamental insights and practical guidance for developing stable, efficient, and environmentally friendly CaHfSe₃-based solar cells. It paves the path for further experimental realization and commercial application.