Cs-Induced Se/S Ratio Variation to Regulate Energy Band Structure for Efficient Sb(S,Se) Bulk Heterojunction Solar Cells.

As an emerging photovoltaic material, antimony selenosulfide (Sb(S,Se)) has attracted considerable attention and research enthusiasm. However, the current solution-processed Sb(S,Se) layers suffer from severe unfavorable energy band structure problems attributed to the vertical gradient-variable Se/S atomic ratio, making it a challenging and prospective subject. Herein, a novel and convenient alkali metal Cs-induced Se/S atomic ratio variation strategy has been developed for the first time to regulate Sb(S,Se) energy band structure through hydrothermal-processed CdS nanorod-arrays (NAs)/Sb(S,Se) bulk heterojunction (BHJ) films. The Cs-induced regulation strategy narrows Se-elemental concentration gradient distribution adjusting effectively Se/S atomic ratio in longitudinal CdS-NAs/Sb(S,Se) BHJ films. This generates a favorable energy band structure, contributing to rapid charge separation and extraction of photogenerated carriers of CdS-NAs/Sb(S,Se) BHJ. Meanwhile, the Cs-induced Se/S ratio variation not only passivates the defect-state concentration and enhances crystal size of CdS-NAs/Sb(S,Se) film, bust also extend the carrier lifetime for Sb(S,Se) BHJ photovoltaic devices. The resulting Cs-Sb(S,Se) BHJ photovoltaic devices exhibit an impressing power conversion efficiency (η) of 8.23%, the highest one currently available for Sb(S,Se) BHJ solar cells. This study will undoubtedly facilitate the development of efficient Sb(S,Se) BHJ devices, and other similar inorganic semiconductor photovoltaic devices.