Fabrication of Photostable Siloxane-Coated Quantum Dots for White-Light-Emitting Diodes

Quantumdots (QDs) are considered as excellent candidatematerialsfor light-emitting diode (LED)-based lighting and display applicationsdue to their excellent optical properties. However, the intrinsicunstable properties of QDs under external environments or the incompatibilitybetween QDs and polymer composites hindered the QD-related applications.Herein, a universal modification method based on the optimizationof QDs was developed for device applications. The highly dispersibleand photostable QDs/siloxane composite was constructed by using thedual silica-encapsulated strategy of core/multishell CdSe/CdS/ZnCdSQDs to improve the performance of QDs. First, core/multishell QD'ssize and components were optimized to enhance stability. Then, QDs@SiO2-OTMS was prepared by a combination of the reverse micro-emulsionmethod and surface modification. Such a double silica surface modificationstrategy is found to be very effective in improving the dispersionby matching the surface energy of QDs@SiO2-OTMS with thatof siloxane resins. The as-prepared QDs@SiO2-OTMS/siloxanefilms had long-term (10 days) stability against heat and moistureand corrosive solution (HCl and NaOH). For the first time, the surfacephotovoltage (SPV) technique was used to study the in situ thermalstability of QDs@SiO2-OTMS, and it was found that surfacedefects were greatly suppressed at high temperatures. Taking theseadvantages, a white LED (WLED) with a color coordinate of (0.336,0.325), color temperature of 5287 K, color gamut 123% National TelevisionSystems Committee (NTSC,1931), and long-time stability at 20 mA hadbeen fabricated by integrating green and red QDs@SiO2-OTMS/siloxane.These results make QDs@SiO2-OTMS/siloxane excellent candidatesfor QD lighting and display applications.