Optimizing Sb2(S,Se)3 thin films: Synergistic tuning of Sb/S ratio and selenization temperature for enhanced quality and deep-trapped defects control

Antimony selenosulfide (Sb 2 (S,Se) 3 ) thin films hold significant potential in the photovoltaic field due to their tunable bandgap, high absorption coefficient (>10 5 cm −1 ), earth-abundant, and low-toxicity constituents. However, serious trapped-carrier recombination at deep-defect levels limits their efficient applications. In this sense, it is urgently necessary to address the issues of the defects and enhancing film properties. This study optimizes solution-processed Sb 2 (S,Se) 3 films by adjusting the antimony/sulfur (Sb/S) atomic ratio in precursors and the post-selenization temperature. Results show that an optimal Sb/S atomic ratio of 2/3.55 in precursors improves the crystallinity, enlarges the grain size, and minimizes the antimony-oxygen (Sb-O) impurities; this suppresses the deep-trapped carriers’ non-radiative recombination, and reduces the defect density in the Sb 2 (S,Se) 3 films. Furthermore, it is found that the selenization at an optimal temperature of 350 °C further increases the grain size, broadens the light absorption, and diminishes the deep-level defects, which is clearly revealed by the transient absorption experiments. This dual-parameter optimization strategy may promote the development of the high-performance Sb 2 (S,Se) 3 films towards high-efficiency photovoltaic applications.