High luminous efficacy and enhanced stability of QDs via a network silica and methylphenyl silicone hybrid for the long-term operation of on-chip white light-emitting diodes with a wide color gamut

We present a facile synthesis for preparing network (NW)-silica-coated greenand red-emitting Cd-based quantum dot [pristine GRQD] powders. Mixing these powders with a methylphenyl silicone (MPS) encapsulant leads to an excellent long-term operation as QD-on-chip white light-emitting diodes (WLEDs). Pristine QDs coated with NW- or chain (Ch)-silica structures (determined by the synthesis temperature) were obtained by a hydrolysis/condensation pathway. Experimentally, in a harsh stability analysis, the as-synthesized NW-silica-coated G(R)QD nanoparticles [G(R)QD@NW-silica NPs] presented evident enhancements against the high blue energy irradiation (similar to 45 mW), a water medium (aging for 1,0 0 0 hr), and heat (to 300 degrees C) when compared with that of pristine G(R)QDs. Notably, the GRQD@NW-silica/MPS hybrid WLEDs (composite QD-WLEDs) were subjected to a high temperature and high humidity condition (85 degrees C/85% RH) for long-term aging, which demonstrated that the luminous flux was maintained at 100% after aging for 1,0 0 0 hr (that of pristine QD-WLEDs decays 23%). Additionally, composite QD-WLEDs were also subjected to a long-term reliability analysis (25 degrees C/60% RH) and exhibited an outstanding reliability with only 17% decay after continuous operation for 2,352 hr, as well as a high luminous efficacy of 81 lm/W and a wide color gamut (122% of NTSC). This study proposes an effective approach for improving the luminous efficiency and long-term operation of composite QD-WLEDs, which have tremendous potential for use in next-generation display applications such as full-color mini-LEDs and micro-LEDs. (c) 2020 Elsevier Ltd. All rights reserved.