Composition-Dependent Aspect Ratio and Photoconductivity of Ternary (Bi_xSb_1–x)₂S₃ Nanorods

The chemical composition, size and shape, and surface engineering play key roles in the performance of electronic, optoelectronic, and energy devices. V 2 VI 3 (V = Sb, Bi; VI = S, Se) group materials are actively studied in these fields. In this paper, we introduce a colloidal method to synthesize uniform ternary (Bi x Sb 1– x ) 2 S 3 (0 < x < 1) nanorods. These nanorods show composition-dependent aspect ratios, enabling their composition, size, and shape control by varying Bi/Sb precursor ratios. It is found that the surface passivation by various thiols (L–SH) efficiently enhances the photoconductivity and optical responsive capability of (Bi x Sb 1– x ) 2 S 3 nanorods when used as active materials in indium tin oxide (ITO)/(Bi x Sb 1– x ) 2 S 3 /ITO optoelectronic devices. Meanwhile, the increase of Sb content causes a gradual deterioration of photoconductivity of thiol-passivated nanorods. We propose that the thiol passivation is able to reduce the number of S vacancies, which act as the recombination centers (trapped states) for photogenerated electrons and holes, and thus boosts the carrier transport in (Bi x Sb 1– x ) 2 S 3 nanorods, and in particular that the composition-related conductivity deterioration is attributed to the increase of unpassivated S vacancies and surface oxidation due to the rise of Sb content.