Realizing efficient near-infrared emission in Cu-In-S/ZnS quantum dots: Aqueous synthesis, optical properties and applications

Ternary I-III-VI quantum dots (QDs) are promising substitutions to Pb and Cd chalcogenide QDs in various applications such as LED, biodetection and sensing. It is urgent to explore near-infrared (NIR) emitting QDs with the advantages of low-cost synthesis and nontoxicity. Herein, water-soluble NIR Cu-In-S/ZnS (CIS/ZnS) QDs were obtained utilizing thioglycolic acid (TGA) and polyethyleneimine (PEI) as the stabilizing molecules in a commercial pressure cooker. Moreover, we detailedly investigated the influence factors on the PL property of CIS QDs and CIS/ZnS QDs including species of sulfur source, reaction time, pH, the dosage of TGA, PEI, Na 2 S, number of ZnS coating layers and the molar ratio of Cu/In. These QDs with adjusting Cu/In ratios show the emission maximum in the range of 710–750 nm. The maximum PL quantum yield (PLQY) of 20 % was acquired for CIS/ZnS QDs with a Cu/In ratio was 0.33/1 and three ZnS layer coating. Finally, we fabricated a NIR pc-LED lamp by using blue LED chips and CIS/ZnS QDs. The device shows a broadband NIR emission centered at 770 nm, which can be applied in night-vision system.