White light-emitting diodes using thermally and photochemically stable fluorescent silica nanoparticles as color-converters†
Trialkoxysilyl terminal groups were directly introduced into fluorescent organic dye molecules by consecutive allylation and hydrosilation reactions; the derivatized dye molecules were then successfully embedded into silica nanoparticles by the Stöber method. Those fluorescent silica nanoparticles (FSNPs) had emission colors corresponding to each fluorescent organic dye used (yellowish-green and red) and showed excellent thermal and photochemical stabilities. A white light-emitting diode (WLED) was fabricated by combining the FSNP/silicone encapsulant composite incorporated with FSNPs having yellowish-green and red emission with a blue InGaN LED (BLED). The resulting three-color RGB FSNP-LED exhibited a good color rendering index (CRI), Ra 86.7, at the correlated color temperature of 5452.6 K and CIE coordinates of (0.3334, 0.3360), indicating that the combination of highly fluorescent silica nanoparticles with LEDs can offer a promising solution for white light sources with high color rendering properties.