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

Abstract Antimony selenosulfide (Sb 2 (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 ( V oc ) for Sb 2 (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 Sb 2 (S,Se) 3 films on TiO 2 /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 Sb 2 (S,Se) 3 film. This facilitates efficient charge transport/separation of photogenerated carriers and boosts significantly the V oc of Sb 2 (S,Se) 3 photovoltaic devices. The champion TA‐Sb 2 (S,Se) 3 planar heterojunction (PHJ) solar cell displays an considerable η of 9.28 % accompanied by an exciting V oc rising to 0.70 V that is currently the highest among Sb 2 (S,Se) 3 ‐based solar cells with efficiencies exceeding 9.0 %. This research is anticipated to contribute to the preparation of high‐quality Sb 2 (S,Se) 3 thin film and the achievement of efficient inorganic Sb 2 (S,Se) 3 PHJ photovoltaic device.