Recent Advances in Two-Dimensional Bismuth Oxysulfide.

Two-dimensional (2D) semiconductors have attracted significant attention for their potential in low-power and high-performance electronic applications. Among these, bismuth oxysulfide (Bi2O2S) has recently emerged as a candidate owing to its wide bandgap, low effective electron mass, and environmental stability. This review summarizes the synthesis strategies and device applications of 2D Bi2O2S. It systematically analyzes recent advancements in synthesis methodologies, ranging from scalable solution-based synthesis to back-end-of-line compatible, low-temperature metal-organic chemical vapor deposition. Furthermore, defect engineering, particularly through oxygen-vacancy control and doping, is discussed as a strategy to modulate the electronic band structure, enhance broadband nonlinear optical properties, and accelerate the photocarrier relaxation kinetics of 2D Bi2O2S. These tunable characteristics have enabled 2D Bi2O2S to be employed in electronic and optoelectronic devices. The review, therefore, discusses recent developments in device applications of Bi2O2S, including field-effect transistors, broadband photodetectors, and flexible photoelectrochemical sensors. Finally, the remaining challenges, such as wafer-scale single-crystal growth and reliable p-type doping, and future research directions are discussed for integrating Bi2O2S into three-dimensional integrated circuits and neuromorphic computing.