Boosting the efficiency of BaZrS₃ solar cells with inorganic delafossite HTLs: A promising alternative to Spiro-OMeTAD

Chalcogenide perovskites are gaining attention as strong candidates for replacing lead halide perovskites owing to their superior optoelectronic characteristics. Among these materials, BaZrS₃ shows great promise as an absorber material for solar cells. However, with only limited available experimental data, there is a clear need for a deeper theoretical understanding to help guide future device development. In this study, we designed a BaZrS₃-based solar cell and used SCAPS-1D simulations to compare the performance of delafossite hole-transport layers (CuFeO₂, CuGaO₂, and CuAlO₂) with the commonly used Spiro-OMeTAD. We analyzed the impact of parameters like acceptor concentration, thickness of the active layer, and the absorber/HTL interface on device performance. Our findings indicate that optimizing the acceptor concentration significantly improves V_OC across all HTLs by enhancing the quasi-Fermi level splitting and strengthening the internal electrostatic field. Enhancing the thickness of the active layer to 800 nm improves photon absorption, boosting about 31 %, resulting in increased charge carrier generation. However, introducing more defects in the absorber drastically reduces the power conversion efficiency (PCE) to approximately 0.09 % owing to greater recombination losses. After optimization, the devices using CuFeO₂, CuGaO₂, CuAlO₂, and Spiro-OMeTAD achieved PCEs of 28.34 %, 27.83 %, 25.04 %, and 27.80 %, respectively. These improvements are mainly due to the higher built-in potential, stronger light absorption, and better charge-carrier dynamics. Overall, this study offers useful theoretical insights to support the development of efficient BaZrS₃-based chalcogenide perovskite solar cells.