| Summary: | Silver-based chalcogenide semiconductors exhibit low toxicity and near-infrared optical properties and are therefore extensively employed in the field of solar cells, photodetectors, and biological probes. Here, we report a facile mixture precursor hot-injection colloidal route to prepare Ag<sub>2</sub>Te<sub>x</sub>S<sub>1−x</sub> ternary quantum dots (QDs) with tunable photoluminescence (PL) emissions from 950 nm to 1600 nm via alloying band gap engineering. As a proof-of-concept application, the Ag<sub>2</sub>Te<sub>x</sub>S<sub>1−x</sub> QDs-based near-infrared photodetector (PD) was fabricated via solution-processes to explore their photoelectric properties. The ICP-OES results reveal the relationship between the compositions of the precursor and the samples, which is consistent with Vegard’s equation. Alloying broadened the absorption spectrum and narrowed the band gap of the Ag<sub>2</sub>S QDs. The UPS results demonstrate the energy band alignment of the Ag<sub>2</sub>Te<sub>0.53</sub>S<sub>0.47</sub> QDs. The solution-processed Ag<sub>2</sub>Te<sub>x</sub>S<sub>1−x</sub> QD-based PD exhibited a photoresponse to 1350 nm illumination. With an applied voltage of 0.5 V, the specific detectivity is 0.91 × 10<sup>10</sup> Jones and the responsivity is 0.48 mA/W. The PD maintained a stable response under multiple optical switching cycles, with a rise time of 2.11 s and a fall time of 1.04 s, which indicate excellent optoelectronic performance.
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