Se‐Elemental Concentration Gradient Regulation for Efficient Sb2(S,Se)3 Solar Cells with High Open‐Circuit Voltages

Antimony selenosulfide (Sb2(S,Se)3), featuring large absorption coefficient, excellent crystal structure stability, benign non‐toxic characteristic, outstanding humidity and ultraviolet tolerability, has recently attracted enormous attention and research interest regarding its photoelectric conversion properties. However, the open‐circuit voltage (Voc) for Sb2(S,Se)3‐based photovoltaic devices is relatively low, especially for the device with a high power conversion efficiency (η). Herein, an innovative Se‐elemental concentration gradient regulation strategy has been exploited to produce high‐quality Sb2(S,Se)3 films on TiO2/CdS substrates through a thioacetamide(TA)‐synergistic dual‐sulfur source hydrothermal‐processed method. The Se‐elemental gradient distribution produces a favorable energy band structure, which suppresses the energy level barriers for hole transport and enhances the driving force for electron transport in Sb2(S,Se)3 film. This facilitates efficient charge transport/separation of photogenerated carriers and boosts significantly the Voc of Sb2(S,Se)3 photovoltaic devices. The champion TA‐Sb2(S,Se)3 planar heterojunction (PHJ) solar cell displays an considerable η of 9.28% accompanied by an exciting Voc rising to 0.70 V that is currently the highest among Sb2(S,Se)3‐based solar cells with efficiencies exceeding 9.0%. This research is anticipated to contribute to the preparation of high‐quality Sb2(S,Se)3 thin film and the achievement of efficient inorganic Sb2(S,Se)3 PHJ photovoltaic device.