White Light-Emitting Diodes With Enhanced Efficiency and Thermal Stability Optimized by Quantum Dots-Silica Nanoparticles

Abstract

White light-emitting diodes (WLEDs) composed of blue LED chip, yellow phosphor, and red quantum dots (QDs) are considered as a potential alternative for the next-generation artificial light source, with their high luminous efficiency (LE) and color-rendering index (CRI). However, the poor stability of QDs-silicone mixture and the optical reabsorption effect between the mixed QDs/phosphor particles severely hinders the wide utilization of QDs-WLEDs. Therefore, in this paper, a silica shell was coated onto the QDs surface to solve the compatibility problem between QDs and phosphor-silicone gel. Then, a QDs-on-chip packaging structure was proposed to reduce the reabsorption energy loss. The prepared QDs@silica nanoparticles (QSNs) exhibited excellent luminescent stability over bare QDs under high-temperature (85 °C) and high-relative humidity (85% RH). With CRI > 90 and R9 > 90, the newly proposed QSNs-WLEDs demonstrated an LE enhancement of 15.7% over conventional mixed-type WLEDs due to the less reabsorption loss. Consequently, the newly proposed QSNs-WLEDs showed 20.5 °C lower QDs working temperature under driving current of 200 mA.