Surface ligand engineering of Ag2Te colloidal quantum dots for a self-powered shortwave infrared photodetector

Abstract

Traditional colloidal quantum dots (CQDs) used for shortwave infrared (SWIR) photodetectors, such as mercury (Hg)-based and lead (Pb)-based CQDs, have been developed with high detectivity and fast responses, but they contain toxic heavy metals. As a non-toxic material, emerging Ag₂Te CQDs provide a new path for the development of the next generation of SWIR photodetectors due to their tunable bandgap, solution-processability, low cost, and environmental friendliness. However, the high surface energy and low bond dissociation energy of Ag₂Te CQDs make them prone to decomposition during high-temperature synthesis, resulting in poor monodispersity. Here, we propose a surface modification strategy based on bifunctional thiol ligands, combined with reaction kinetics regulation, to achieve stable synthesis of Ag₂Te CQDs and discuss their application in SWIR photodetectors. The results show that the synthesized Ag₂Te CQDs have high monodispersity, and they help realize a wide response self-powered photodiode from 400 to 1600 nm at 0 V bias. The specific detectivity of the SWIR Ag₂Te CQD photodetector is of the order of 10¹⁰ Jones, the −3 dB bandwidth reaches 211 kHz, the linear dynamic range exceeds 74 dB, and the fast response time is 13.3 μs at room temperature (25 °C). In addition, benefiting from its excellent SWIR detection performance, we further demonstrate the application of the Ag₂Te CQD photodetector in non-contact transmission pulse monitoring.