Heat and water-resistant sol-gel synthesized quantum dot/methacryl siloxane phosphor composite material

Abstract

I report the fabrication of a siloxane-encapsulated quantum dot (QD) film (QD/siloxane (methacryl) film), which contains thermally stable siloxane bonds and linkages between QD and siloxane matrix. With the help of both factors that create a synergy effect on the QD/siloxane (methacryl) film, which exhibits stable emission intensity for over 1 month even at elevated temperature and humidity compared to QD-commercial hydrocarbon based polymer film (QD/hydrocarbon (acryl) film) and QD/siloxane (epoxy) film, which has no bonding forms between QD and siloxane matrix. The QD/siloxane (methacryl) films are solidified via free radical addition reaction between methacryl functional group of siloxane resin and ligand molecules (oleic acid) on QDs. I prepare the QD/siloxane (methacryl) resin by non-hydrolytic sol-gel condensation reaction of silane precursors with QDs blended in the precursor solution, forgoing ligand-exchange of QDs. The resulting QD/siloxane (methacryl) resin remains optically clear after 40 days of storage, in contrast to other QD-containing commercial hydrocarbon-based polymer resin, which turn turbid and ultimately form sediments. QDs also disperse uniformly in the QD/siloxane (methacryl) film, whose photoluminescence (PL) quantum yield (QY) remains nearly unaltered under harsh conditions

for example, 85 °C/5% relative humidity (RH), 85 °C/85% RH, strong acidic, and strong basic environments for 40 days of aging time. The QD/siloxane (methacryl) film appears to remain equally emissive even after being immersed into boiling water (100 °C) and oxygen plasma treatment. Interestingly, the PL QY of the QD/siloxane (methacryl) film noticeably increases and it retains increased PL QY when the film is exposed to a moist environment, which opens a new, facile avenue to curing dimmed QD-containing films. In addition, this dissertation gives a way of improving photostability of QD-containing composite film. Given its excellent stability, the QD/siloxane (methacryl) film is best suited in display applications, particularly as a PL-type down-conversion layer.