Potential of Bifunctional SnS to Substitute Spiro for High‐Efficiency Full‐Inorganic Sb ₂ (S,Se) ₃ Solar Cells With n‐i‐p Configuration

Sb ₂ (S,Se) ₃ exhibits a huge potential in the field of thin‐film photovoltaics, attributed to superior photo‐electronic features. However, the long‐term stability of highly efficient devices is strongly dependent on the organic Spiro functional layer. Herein, the use of inorganic SnS as an alternative hole transport layer (HTL) to Spiro in devices is initially assessed for comparison via the SCAPS‐1D software. This work indicated the attractive function of SnS HTL in improving power conversion efficiency (PCE) by generating a higher electric field at the back interface, suppressing non‐radiative recombination. Most importantly, the (111)‐SnS was likely formed onto (221)‐Sb ₂ (S,Se) ₃ , attributed to a small lattice mismatch (−1.15%), which facilitates carrier separation and transport. Additionally, the SnS could also enhance light‐harvesting ability, playing an extra absorber. Compared with the Sb ₂ (S,Se) ₃ /Spiro interface, the recombination at Sb ₂ (S,Se) ₃ /SnS interface was significantly suppressed with a benign band alignment. Ultimately, a PCE of 23.42% was predicted, in which the thicknesses are 500 and 300 nm, defect densities are 1 × 10 ¹⁴ and 1 × 10 ¹¹  cm ⁻³ , and doping concentrations are 1 × 10 ¹³ and 1 × 10 ¹⁹  cm ⁻³ for Sb ₂ (S,Se) ₃ and SnS, respectively. This work will be useful for regulating carrier recombination and developing bifunctional HTL for highly efficient full‐inorganic Sb ₂ (S,Se) ₃ solar cells.