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Transition metal dichalcogenides (TMDs) are a category of promising two-dimensional (2D) materials for the optoelectronic devices, and their unique characteristics include tunable band gap, nondangling bonds as well as compatibility to large-scale fabrication, for instance, chemical vapor deposition (CVD). MoS2is one of the first TMDs that is well studied in the photodetection area widely. However, the low photoresponse restricts its applications in photodetectors unless the device is applied with ultrahigh source–drain voltage (VDS) and gate voltage (VGS). In this work, the photoresponse of a MoS2photodetector was improved by a chemical in situdoping method using gold chloride hydrate. The responsivity and specific detectivity were increased to 99.9 A/W and 9.4 × 1012Jones under low VDS(0.1 V) and VGS(0 V), which are 14.6 times and 4.8 times higher than those of a pristine photodetector, respectively. The photoresponse enhancement results from chlorine n-type doping in CVD MoS2which reduces the trapping of photoinduced electrons and promotes the photogating effect. This novel doping strategy leads to great applications of high-performance MoS2photodetectors potentially and opens a new avenue to enhance photoresponse for other 2D materials.