Tin Chalcogenide Colloidal Quantum Dots for Infrared Photodetection

Printable, flexible and low-cost photodetectors with sensitivity in the near-infrared (NIR, 700-2500nm) window are in high demand. Much research on infrared active colloidal quantum dots (CQDs) have been conducted based on lead or mercury chalcogenides. However, environment-friendly alternatives with tunable sensitivity in the NIR and high performance should be investigated to better protect our environment. We have developed silver chalcogenide CQDs and demonstrated their application in NIR photodetection, including Ag₂Se and Ag₂Te QDs with detection up to 1.2 µm and 1.4 µm^1,2. To further push the sensitivity to longer wavelength, we have been developing tin telluride (SnTe) CQDs. SnTe QDs possess good optical properties in the range of 1.5-2.5 µm. So far, only a few studies were reported; the reaction mechanism is poorly understood, the synthesis is challenging and the products are prone to oxidation.<br/><br/>Our SnTe CQDs were synthesized with tin precursors that are less toxic, less expensive and less susceptible to oxidation than that commonly used (Bis(bis(trimethylsilyl)amino tin(II))³. The reaction was optimized by tuning different parameters (ligands, temperature, tin precursor, etc.) to reduce the oxidation and obtain monodispersed CQDs. We were able to obtain CQDs of 12 nm with an optical sensitivity up to 2.5 µm and good stability (weeks) under air. Additionally, SnTe CQDs can be coated to obtain more stable CQDs under air. The absorbance wavelength can also be tuned with this doping from 1.2 µm to 2.5 µm with a good control by changing the reaction time.<br/><br/>Our developed SnTe CQDs can offer a low-toxicity route for low-cost solution-processable fabrication of high-performance infrared photodetectors with sensitivity up to 2.5 µm.<br/> <br/>1. <i>ACS Appl. Nano Mater.</i> <b>2021</b>, 4, 13587−13601<br/>2. <i>ACS Appl. Nano Mater.</i> <b>2020</b>, 3, 12209−12217<br/>3<i>. J. Am. Chem. Soc</i>. <b>2022</b>, 144, 6251−6260