Drift-diffusion modeling-guided interface optimization in BaHfS3 chalcogenide perovskite solar cells

Chalcogenide perovskites are promising photoabsorbers for next-generation photovoltaics owing to their intrinsic stability, non-toxicity, and favorable optoelectronic properties. To evaluate their potential, solar cell capacitance simulator-one dimensional (SCAPS-1D) drift-diffusion simulations were performed on six representative compounds to assess charge transport characteristics. BaHfS₃ exhibited the highest carrier mobility, longest diffusion length, and strongest light absorption. BaHfS₃-based perovskite solar cells (PSCs) were modeled in an n-i-p architecture incorporating six different electron and hole transport layers (ETLs and HTLs) to investigate interfacial energy-level alignment. Titanium dioxide (TiO₂) emerged as the optimal ETL, offering the conduction band offset (CBO) and valence band offset (VBO) of 0 eV and 1.9 eV, respectively.2,2,7,7-tetrakis(N,N-di-p-methoxyphenylamine)-9,9spirobifluorene(Spiro-OMeTAD) was the best-performing HTL, with a VBO of 0.1 eV and CBO of 1.8 eV, enabling efficient hole extraction. Further optimization revealed that 1.0 $\mu m$ thick perovskite layer, doping concentrations of 10¹⁸-10²⁰ cm⁻³, and low defect density (10¹⁴ cm⁻³) significantly suppressed recombination. Additionally, reducing series resistance (2 Ω cm²) and increasing the shunt resistance (>1000 Ω cm²) significantly improved performance. Impedance and capacitance analyses confirmed excellent interfacial quality, with TiO₂/BaHfS₃/Spiro-OMeTAD configurations exhibiting highest recombination resistance. Under optimized conditions, maximum power conversion efficiency of 31 % was achieved, highlighting BaHfS₃ as a highly efficient photosensitizer for future PSC development.