High photovoltaic performance of an emerging lead-free chalcogenide perovskite BaHfS3 under high pressure

Chalcogenide perovskites have received much attention in photovoltaic research due to their stability, non-toxicity, and lead-free nature. The structural, electronic, and optical properties of BaHfS 3 under different pressure conditions were investigated using DFT and its photovoltaic performance was estimated using the one-dimensional solar cell capacitance simulator SCAPS-1D. By increasing the pressure, the lattice parameter and band gap decrease without affecting the direct nature of the band gap at the Γ- point. The elastic constants follow the Born-Huang stability criterion and show the mechanical stability of the composition even under compressive pressure conditions. The Poisson's ratio is in the range of 0.28–0.36 and the ratio B/G > 1.75 indicates the ductile and soft nature of the material. The estimated universal anisotropic index values under different pressure conditions confirm the anisotropic nature of BaHfS 3 . The DFT-based calculation to investigate electronic and optical properties reveals that the increase in pressure leads to more dispersive band edges resulting in lower effective masses and consequently larger carrier mobilities along with improved optical properties. The SCAPS-1D is used to analyze the performance of a perovskites solar cell module FTO/ETL/BaHfS 3 /HTL/Au under various pressure conditions with the absorber layer BaHfS 3 . The absorber layer of BaHfS 3 at 25 GPa has high bipolar carrier mobility and a direct band gap value of 1.30 eV with a PCE of 28.68 % in the visible region, indicating BaHfS 3 as a promising lead-free flexible photovoltaic material.