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.