Self-Powered Photodetection in AgBiS ₂ Nanocrystals Synthesized from AgBi-Mixed-Metal Thiolate

AgBiS 2 has emerged as a promising optoelectronic material owing to its high absorption coefficient, environmentally friendly and abundant components, offering a sustainable alternative to lead- and cadmium-based chalcogenides. Realizing the full potential of AgBiS 2 devices, however, requires scalable synthesis routes that include development of suitable precursors and minimize the use of harsh solvents, elevated temperatures, inert environments, etc. Here, we present a facile, solvent-free synthesis of phase pure AgBiS 2 nanocrystals (NCs) at room temperature and under ambient conditions, enabled by the AgBi mixed-metal thiolate (AgBi-MMT) precursor complex. The initial choice of metal salts determines the nature of the metal thiolate intermediate complex, which subsequently influences the quality of the resulting AgBiS 2 NCs. As a single-source precursor of the metals, AgBi-MMT enables controlled release of Ag + and Bi 3+ ions, yielding phase-pure AgBiS 2 NCs. Furthermore, the MMT that is derived from AgI and BiI 3 precursors promotes in situ surface passivation of the AgBiS 2 NCs by iodide ions by trapping molecular I 2 within its matrix. Under illumination, these iodide ions undergo reversible migration, generating a built-in potential and enabling self-powered photodetection in devices prepared from the as-synthesized NCs. This work expands the synthesis methodology of AgBiS 2, highlighting the importance of metal thiolates as precursors in nanomaterial syntheses, and influence of iodine species in photo-operational devices.