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

Abstract

Quantum dots (QDs) are considered as excellent candidate materials for light-emitting diode (LED)-based lighting and display applications due to their excellent optical properties. However, the intrinsic unstable properties of QDs under external environments or the incompatibility between QDs and polymer composites hindered the QD-related applications. Herein, a universal modification method based on the optimization of QDs was developed for device applications. The highly dispersible and photostable QDs/siloxane composite was constructed by using the dual silica-encapsulated strategy of core/multishell CdSe/CdS/ZnCdS QDs to improve the performance of QDs. First, core/multishell QD’s size and components were optimized to enhance stability. Then, QDs@SiO2-OTMS was prepared by a combination of the reverse micro-emulsion method and surface modification. Such a double silica surface modification strategy is found to be very effective in improving the dispersion by matching the surface energy of QDs@SiO2-OTMS with that of siloxane resins. The as-prepared QDs@SiO2-OTMS/siloxane films had long-term (10 days) stability against heat and moisture and corrosive solution (HCl and NaOH). For the first time, the surface photovoltage (SPV) technique was used to study the in situ thermal stability of QDs@SiO2-OTMS, and it was found that surface defects were greatly suppressed at high temperatures. Taking these advantages, a white LED (WLED) with a color coordinate of (0.336, 0.325), color temperature of 5287 K, color gamut 123% National Television Systems Committee (NTSC,1931), and long-time stability at 20 mA had been fabricated by integrating green and red QDs@SiO2-OTMS/siloxane. These results make QDs@SiO2-OTMS/siloxane excellent candidates for QD lighting and display applications.