Two‐Dimensional Few‐Layer Selenides: From Materials to Applications

Two‐dimensional (2D) few‐layer selenides attract much attention due to their unique electronic structures and layer‐dependent properties, which differ markedly from those of bulk layered selenides. Especially some transition metal diselenides, which undergo a transition from an indirect bandgap to a direct bandgap with reduced layer number, can meet the specific requirements of high‐performance optoelectronic devices. However, the stable, controllable, and large‐scale synthesis of few‐layer selenides remains a key bottleneck limiting their development. Furthermore, employing strategies such as edge engineering, heterostructure construction, and phase engineering to regulate their properties is equally important for maximizing their application value. Herein, the structural characteristics and layer‐dependent properties of various 2D few‐layer selenides are systematically introduced. Both top‐down and bottom‐up synthesis methods are emphasized. The relationship between the properties of 2D few‐layer selenides and their applications in energy storage, electronics, optoelectronics, thermoelectricity, and catalysis is revealed. Recent developments and potential directions for future research are discussed. This comprehensive review is expected to advance theoretical research on 2D few‐layer selenides and provide insightful guidance for their future functionalization and large‐scale applications.