In-situ TiO2-Coated CsPbBr3 quantum dots with enhanced stability, photoluminescence quantum yields, and charge transport properties

Cesium lead bromide quantum dots (CsPbBr 3 QDs) have suffered from instability against the environmental factors in broad applications due to the inherent perovskite properties. Here, TiO 2 coating on CsPbBr 3 QDs by ex-situ and in-situ methods was performed to prevent the agglomeration of the nanocrystals and to improve the stability of CsPbBr 3 QDs without heat treatment at high temperature. By focusing on the in-situ coating method, this work also reported the effects of injection temperature of titanium precursor into the QDs solution from 25 °C to 170 °C on the morphological, structural, and optical properties of the obtained TiO 2 -coated CsPbBr 3 QDs. The in-situ coated samples were non-agglomerated and remained the original shape and crystal structure of CsPbBr 3 QDs, whereas the ex-situ coated samples were completely agglomerated. The in-situ samples exhibited a significant stability improvement against toluene, ultrasonication treatment in water, and light illumination (all with the photoluminescence intensity greater than 50%). Furthermore, the in-situ TiO 2 -coated CsPbBr 3 QDs were proved to use as a good charge transport material in the photoelectrochemical cell. The results demonstrated the remarkable enhancement of photocurrent, owing to a suitable alignment of energy levels of TiO 2 and CsPbBr 3 and a stable structure of QDs, when compared to that of the as-synthesized CsPbBr 3 QDs. The present study provides a new perspective to utilize stable TiO 2 -coated CsPbBr 3 QDs in various photoelectrochemical applications.