Controlled Synthesis of Ultrathin 2D β‐In2S3 with Broadband Photoresponse by Chemical Vapor Deposition

β‐In 2 S 3 is a natural defective III–VI semiconductor attracting considerable interests but lack of efficient method for its 2D form fabrication. Here, for the first time, this paper reports controlled synthesis of ultrathin 2D β‐In 2 S 3 flakes via a facile space‐confined chemical vapor deposition method. The natural defects in β‐In 2 S 3 crystals, clearly revealed by optical spectra and optoelectronic measurement, strongly modulate the (opto)‐electronic of as‐fabricated β‐In 2 S 3 and render it a broad detection range from visible to near‐infrared. Particularly, the as‐fabricated β‐In 2 S 3 photodetector shows a high photoresponsivity of 137 A W −1 , a high external quantum efficiency of 3.78 × 10 4 %, and a detectivity of 4.74 × 10 10 Jones, accompanied with a fast rise and decay time of 6 and 8 ms, respectively. In addition, an interesting linear response to the testing power intensities range is observed, which can also be understood by the presence of natural defects. The unique defective structure and intrinsic optical properties of β‐In 2 S 3 , together with its controllable growth, endow it with great potential for future applications in electronics and optoelectronics.