Mixed Halide Passivation of AgBiS₂ Quantum Dots for High-Performance Photodetectors

AgBiS2 quantum dots (QDs) have been undergoing rapid development in recent years because of their environmental friendliness, abundant elemental reserves, and high optical absorption coefficients. However, previously reported ligand exchange methods for AgBiS2 CQDs have been ineffective in passivating surface defects, thereby limiting their potential for optoelectronic applications. In this study, we propose a facile solution-phase ligand exchange method assisted by mixed halides for the AgBiS2 CQDs. This approach, involving AgCl and other halides, effectively suppresses surface defects and enhances the photodetector (PD) performance. The PD exhibits significantly improved optoelectronic characteristics, with a responsivity of 0.27 A W–1 and a low noise power density of 6.52 × 10–9 A Hz–0.5, achieving the highest specific detectivity of 2 × 1012 Jones compared to previous reports of AgBiS2 CQD PDs. This mixed halide passivation strategy introduces new insights into enhancing the performance of AgBiS2 CQDs in PD applications.