Nanoinks composed of quantum dots (QDs) are applied in light-receiving devices and light-emitting devices such as solar cells and displays. However, since the most widely used QDs, PbS and CdS, are toxic and environmentally concerning, alternative materials need to be developed. We synthesized and analyzed Ag chalcogenide nanoparticles, including AgBiS2 and Ag2S nanoparticles, which are eco-friendly materials. AgBiS2 and Ag2S QD films were prepared by spin-coating nanoparticle solutions and subsequent heat treatment. The effects of the heat treatment on residual ligands and photoluminescence were determined by surface analysis. The photocurrent response of the AgBiS2 and Ag2S QD films was measured in the near-infrared region, and the effect of the heat treatment temperature was investigated. The results indicate that AgBiS2 and Ag2S are prospective materials for near-infrared photodetectors.

Compact and highly sensitive near-infrared photodetectors that are operable at room temperature are required for light detection and ranging and medical devices. Two-dimensional (2D) PtSe2, a transition metal dichalcogenide, is a candidate material for near-infrared light detection. However, the photoresponse properties of 2D PtSe2 are currently inferior to those of commercial materials. The localized surface plasmon resonance of Au has been widely used for photoelectric field enhancement and in photochemical reactions associated with phase relaxation from plasmon states that occur at specific wavelengths. Spherical Au nanocolloids exhibit an extinction peak in the visible light region, whereas nanorods can be tuned to exhibit the extinction peak in the near-infrared region by controlling their aspect ratio. In this study, hybrid Au nanorod/2D PtSe2 structure was fabricated via spin coating nanorods, with plasmon peaks in the near-infrared region, on 2D PtSe2. Furthermore, the effect of the concentration of the nanorod solution on the photoresponse of nanorod/2D PtSe2 was investigated. The photocurrent of 5 nM Au nanorod-coated 2D PtSe2 was fivefold higher than that of bare 2D PtSe2. The responsivity was maximum 908 μW/A at 0.5 V bias voltage. In addition, the photocurrent enhancement mechanism by Au nanorods is discussed.

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