Halide Removal and SiO 2 @TiO 2 Composite Passivation: Enhancing InP QD Photooxidation Stability for WLEDs

Abstract

The stability of quantum dots (QDs) is primarily limited by photooxidation of their surface, and the adsorption of water and oxygen significantly affects this. Under photoexcitation, adsorbed H2O and O2 undergo photochemical reactions with the QD surface, thereby accelerating oxidative degradation. Therefore, minimizing water and oxygen adsorption is crucial for improving the inherent stability of QDs. Herein, we reveal that excess halide ions adsorbed on indium phosphide (InP) QDs promote water adsorption through synergistic coordinative interactions and hydrogen bonding between the surface halides and atmospheric water molecules, which substantially increase surface water coverage and severely deteriorate the stability of InP QDs. To address this challenge, we propose a two-step surface-engineering strategy: (i) removing excess surface halide ions to eliminate the main driving force for water adsorption, and (ii) constructing a SiO2@TiO2 composite passivation layer, where TiO2 fills the mesopores within the SiO2 matrix while modulating the interfacial hydrophobicity. The resulting QD@SiO2@TiO2 nanocomposite utilizes a synergistic mechanism of “halide removal-composite passivation”, significantly improving its environmental and photochemical stability. The white-light-emitting diodes (WLEDs) fabricated using this material exhibit a T85 lifetime exceeding 530 hours, highlighting its enormous potential in QD-based optoelectronic device applications.