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

AgBiS2 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 AgBiS2 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 AgBiS2 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 AgBiS2 NCs. As a single-source precursor of the metals, AgBi-MMT enables controlled release of Ag+ and Bi3+ ions, yielding phase-pure AgBiS2 NCs. Furthermore, the MMT that is derived from AgI and BiI3 precursors promotes in situ surface passivation of the AgBiS2 NCs by iodide ions by trapping molecular I2 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 AgBiS2, highlighting the importance of metal thiolates as precursors in nanomaterial syntheses, and influence of iodine species in photo-operational devices.