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 (V_oc) 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 V_oc 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 V_oc 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.