Encapsulation of CsPb₂Br₅ in TiO₂ Microcrystals to Enhance Environmental Stability

All-inorganic lead halide perovskite has emerged as an attractive semiconducting material due to its unique optoelectronic properties. However, its poor environmental stability restricts its broad application. Here, a simple method for the fabrication of CsPb₂Br₅/TiO₂ is investigated. The introduction of p-aminobenzoic acid, which has two functional groups, is critical for the capping of amorphous TiO₂ on CsPb₂Br₅. After calcination at 300 °C, amorphous TiO₂ crystallizes into the anatase phase. The CsPb₂Br₅/TiO₂ NCs show high long-term stability in water and enhanced stability against ultraviolet radiation and heat treatment, owing to the chemical stability of TiO₂. More importantly, photo-electrochemical characterizations indicate that the formation of TiO₂ shells can increase the charge separation efficiency. Hence, CsPb₂Br₅/TiO₂ exhibits improved photoelectric activity owing to the electrical conductivity of the TiO₂ in water. This study provides a new route for the fabrication of optoelectronic devices and photocatalysts based on perovskite NCs in the aqueous phase. Furthermore, the present results demonstrate that CsPb₂Br₅/TiO₂ NCs has considerable potential to be used as a photoelectric material in optical sensing and monitoring.