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

Abstract

Cesium lead bromide quantum dots (CsPbBr3 QDs) have suffered from instability against the environmental factors in broad applications due to the inherent perovskite properties. Here, TiO2 coating on CsPbBr3 QDs by ex-situ and in-situ methods was performed to prevent the agglomeration of the nanocrystals and to improve the stability of CsPbBr3 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 TiO2-coated CsPbBr3 QDs. The in-situ coated samples were non-agglomerated and remained the original shape and crystal structure of CsPbBr3 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 TiO2-coated CsPbBr3 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 TiO2 and CsPbBr3 and a stable structure of QDs, when compared to that of the as-synthesized CsPbBr3 QDs. The present study provides a new perspective to utilize stable TiO2-coated CsPbBr3 QDs in various photoelectrochemical applications.