Non-toxic silver telluride colloidal quantum dot mid-infrared photodetector

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Abstract
As demand for sustainable and biocompatible technologies grows, low-toxicity mid-infrared materials, such as silver chalcogenides, have attracted significant interest. Herein, we report mid-wavelength infrared tunable Ag 2 Te colloidal quantum dots through a post-growth method starting from short-wavelength infrared Ag 2 Te colloidal quantum dots. Using the synthesized Ag 2 Te colloidal quantum dots, we successfully fabricate a photodetector covering the full mid-wavelength infrared spectral range (3–5 μm) with an onset wavelength extending to 6.9 μm. At 78 K, the photodetectors exhibit a photoresponse time of 230 ns (rise) and 576 ns (fall). Responsivity varies from 1.9 × 10 -3  A W −1 at 0.02 V to 1.1 A W −1 at 0.5 V, depending on the applied bias, and the specific detectivity of the device is 1.2 × 10 9 Jones at 0.02 V. The measured noise-equivalent temperature difference of 0.3 K enables us to reliably distinguish temperature variations between 37 °C and 40 °C, directly enabling the diagnosis of fever-level body temperatures.
Funding Information
  • National Research Foundation of Korea (NR068167)
  • National Research Foundation of Korea (NR059609)
  • National Research Foundation of Korea (RS-2025-25437404)
  • National Research Foundation of Korea (RS-2024-00407943)

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