Photoelectrochemically Active and Environmentally Stable CsPbBr 3 /TiO 2 Core/Shell Nanocrystals

Abstract Inherent poor stability of perovskite nanocrystals (NCs) is the main impediment preventing broad applications of the materials. Here, TiO 2 shell coated CsPbBr 3 core/shell NCs are synthesized through the encapsulation of colloidal CsPbBr 3 NCs with titanium precursor, followed by calcination at 300 °C. The nearly monodispersed CsPbBr 3 /TiO 2 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, TiO 2 shell coating can effectively suppress anion exchange and photodegradation, therefore dramatically improving the chemical stability and photostability of the core CsPbBr 3 NCs. More importantly, photoluminescence and (photo)electrochemical characterizations exhibit increased charge separation efficiency due to the electrical conductivity of the TiO 2 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.