Two-dimensional (2D) ternary wide-bandgap semiconducting materials have great potential in power device,flexible electronic device,short-wavelength light emitting diodes (LEDs) and photodetectors due to the controllable bandgap,strong light-material interaction,and controlled freedom degree of stoi-chiometry variation.However,it is still a great challenge to precisely control the growth of high-quality 2D ternary wide-bandgap semiconducting materials due to the variety of components,which hinders their development for practical applications.In this work,high-quality 2D ternary bismuth oxybromide single-crystal nanosheets with a high yield were prepared by space-confined chemical vapor deposition(CVD) method.The devices based on 2D ultrathin BiOBr single-crystal nanoflakes show a high UV detect-ing performance including low dark current (Idark) of 1.46 pA and high responsivity (R),external quantum efficiency (EQE) and detectivity (D*) of 14.96 A W-1,5460％,and 5.74 × 1010 Jones,respectively,as well as fast response process (τrise =80 ms,τdecay =40 ms).The excellent UV performance can be ascribed to the photogating effect by trapped states,which endow it with great potential for high-performance UV detectors.