Recent Progress in Surface Engineering of AgBiS ₂ Nanocrystals for Nontoxic and Efficient Photovoltaics

Silver bismuth sulfide (AgBiS 2 ) nanocrystals have recently emerged as eco‐friendly semiconductors, achieving power conversion efficiencies above 10%. These improvements are largely driven by surface engineering, which reduces mid‐gap states and enhances charge transport and film quality. This review summarizes four major surface engineering strategies for AgBiS 2 NCs solid‐state ligand exchange, solution‐phase ligand exchange, direct synthesis, and full passivation, highlighting their principles and representative achievements. We also discuss emerging approaches that combine chemical control with structural design, offering pathways toward scalable, stable, and high‐performance AgBiS 2 photovoltaics.