Non-Toxic CuInS 2 /ZnS Colloidal Quantum Dot for Near-Infrared Light-Emitting Diodes.

Ternary CuInS 2 quantum dots (QDs) with photoluminescence tunable from the visible to near-infrared (NIR) region are promising light-emitters for consumer electronics due to the absence of toxic elements such as Pb, Cd or As. Despite the compelling performance of visible emitting CuInS 2 QDs, reports on NIR emission remain limited with modest efficiencies at wavelengths beyond 900 nm. In this work, we describe the facile synthesis of NIR emitting CuInS 2 /ZnS QDs through the use of a binary sulfur precursor, consisting of 1-dodecanethiol (DDT) and hexamethyldisilathiane (HMDS). The reactive HMDS facilitated faster nucleation and led to a higher density of emissive Cu-deficiency sites. The resulting QDs exhibit high photoluminescence quantum efficiency (PLQE) of 65% at a long emission wavelength of 920 nm. Using these QDs, we fabricated NIR light-emitting diodes (LED) which attained an external quantum efficiency (EQE) of 8.2%. This efficiency is comparable to the best reported PbS and InAs QD LEDs, and its emission wavelength exceeds that of lead iodide perovskites. This work thus marks one of the first reports of efficient NIR LEDs based on environmentally-benign CuInS 2 QDs and may open up promising new applications in consumer electronic products. This article is protected by copyright. All rights reserved.