Ionic liquid alkyl chain regulated highly stable and luminescent silica-coated perovskite quantum dots for bright white light-emitting diodes

Silica-coated perovskite quantum dots (QDs), which exhibit exceptional photophysical properties, hold great promise for various optoelectronic applications. Nonetheless, the issue of insufficient stability poses a significant challenge to their continued advancement and widespread adoption. Herein, we present a novel approach for the synthesis of silica-coated CH3NH3PbBr3 (CH3NH3 = MA) QDs with exceptional stability and luminescence, which utilized hydrophobic ionic liquids (ILs) with unlike alkyl chain lengths as surface ligands. As the alkyl chain length of the hydrophobic ILs increased, we observed a blue-shift in the wavelength and a reduction in the time required to reach maximum fluorescence for the silica-coated perovskite QDs. It not only effectively prevents QD aggregation but also accelerates the formation rate of the SiO2 shell. The introduction of ILs generated the enhancement of photoluminescence quantum yield (PLQY) from 85% for the pristine sample to 92.83% for ILs treated C16-QDs@SiO2. Furthermore, the stability of the ILs-treated C16-QDs@SiO2 was notably enhanced, with the fluorescence intensity retaining 80.5% after 40 days of storage. The as-prepared white light emitting diode (LED) displayed a high color rendering index (CRI) of 75.3 and a correlated color temperature (CCT) of 7529 K. This work provides an alternative strategy to solve the challenging stability issue of silica-coated perovskite QDs and promote the silica-coated perovskite QDs to the practical application in solid-state LEDs.