Achieving Tunable Band Structure and Photocarrier Dynamics by Regulating 2D Atomic Layer Stacking Toward High-Performance Self-Powered Broadband and Deep-UV Photodetection

2D materials with unique layer-dependent electronic structure can bring precise control to their photocarrier dynamics for optimizing and expanding optoelectronic applications, while the challenge of controlling layer stacking makes the layer dependency law still underexplored in emerging 2D ternary metal chalcogenides. Herein, 2D rhombohedral-phase ZnIn2S4 (R-ZIS) with controllable layer thickness is achieved by confined-growth strategy in high yield, exhibiting continuously tunable direct bandgap (2.39-2.77 eV) with evident upshift of conduction band minimum (CBM) and Fermi level (EF), demonstrated arising from the synergistic effect of reduced interlayer interaction with inevitably increasing Zn defects. Remarkably, the carrier dynamics of R-ZIS in photoelectrochemical (PEC) device is successfully regulated by adjusted CBM and EF, resulting in continuously tunable optical absorption band, photocarrier separation efficiency, self-powered capability, and dark current noise. Beneficial from tailored band structure and carrier dynamics, self-powered PEC-type photodetector with broadband photoresponse (254-765 nm), is achieved fast response speed (12.3/5.3 ms) and high responsivity (90.29 mA W-1) in multilayer R-ZIS, while deep-UV photodetector with ultra-high specific detectivity (1.62 x 1012 Jones) at 254 nm in monolayer R-ZIS, exhibiting the record performance in both fields. This work motivates the development of tailored band structure for 2D-materials-based optoelectronic devices in strategy and mechanism.