Photoelectrochemically active and environmentally stable cspbbr₃/tio₂ core/shell nanocrystals

Inherent poor stability of perovskite nanocrystals (NCs) is the main impediment preventing broad applications of the materials. Here, TiO₂ shell coated CsPbBr₃ core/shell NCs are synthesized through the encapsulation of colloidal CsPbBr₃ NCs with titanium precursor, followed by calcination at 300 °C. The nearly monodispersed CsPbBr₃/TiO₂ core/shell NCs show excellent water stability for at least three months with the size, structure, morphology, and optical properties remaining identical, which represent the most water-stable inorganic shell passivated perovskite NCs reported to date. In addition, TiO₂ shell coating can effectively suppress anion exchange and photodegradation, therefore dramatically improving the chemical stability and photostability of the core CsPbBr₃ NCs. More importantly, photoluminescence and (photo)electrochem-ical characterizations exhibit increased charge separation efficiency due to the electrical conductivity of the TiO₂ shell, hence leading to an improved photoelectric activity in water. This study opens new possibilities for optoelectronic and photocatalytic applications of perovskites-based NCs in aqueous phase.