Silica-embedded quantum dots as downconverters of light-emitting diode and effect of silica on device operational stability

Highly bright, blue-to-yellow light-convertable CuInS2 (CIS)/ZnS core/shell quantum dots (QDs) are first synthesized and then embedded into silica phase via a microemulsion. Effects of silica embedding on photoluminescence of CIS/ZnS QDs are investigated. Bare and silica-embedded QDs are combined, respectively, with a blue light-emitting diode (LED) pumping source for white QD-LED fabrication. These two white QD-LEDs are identically subjected to the continous operation at a forward current of 20 mA for an extended period of time up to 70 h. As the operation lasts, a bare QD-based device suffers from a steady reduction of QD emission, while the QD emission of silica-embedded QD-based one increases rather rapidly during the initial period of operational time and then begins to weaken thereafter. The above different behaviors in device stability are described in conjunction with photochemical oxidation of QDs. (C) 2013 Elsevier B.V. All rights reserved.