Quasiepitaxy Strategy for Efficient Full‐Inorganic Sb₂S₃ Solar Cells

Antimony sulfide (Sb 2 S 3 ) as a wide‐bandgap, nontoxic, and stable photovoltaic material reveals great potential for the uppermost cells in Si‐based tandem cell stacks. Sb 2 S 3 solar cells with a compatible process, acceptable cost, and high efficiency therefore become the mandatory prerequisites to match silicon bottom cells. The performance of vacuum processed Sb 2 S 3 device is pinned by bulk and interfacial recombination. Herein, a thermally treated TiO 2 buffer layer induces quasiepitaxial growth of vertical orientation Sb 2 S 3 absorber overcoming interface defects and absorber transport loss. Such novel growth could pronouncedly improve the open‐circuit voltage ( V oc ) due to the superior interface quality and intraribbon transport. The epitaxial rough Sb 2 S 3 surface shows a texturized‐like morphology. It is optimized by tuning the grain sizes to form strong light trapping effect, which further enhances the short‐circuit current density ( J sc ) with a 16% improvement. The final optimal device with high stability obtains a power conversion efficiency of 5.4%, which is the best efficiency for full‐inorganic Sb 2 S 3 solar cells. The present developed quasiepitaxy strategy supports a superior interface, vertical orientation, and surface light trapping effect, which provides a new perspective for efficient noncubic material thin film solar cells.