Stability Enhancement of CsPbBr3 Quantum Dots by Coating TiO2 as a Surface Encapsulation

The cesium lead bromide quantum dots (CsPbBr3 QDs) have exhibited the excellent optical properties which have been widely used in the applications of optoelectronic and photoelectrochemical devices. However, the instability of CsPbBr3 QDs against the environment factors has been a major obstacle hindering the commercialization of corresponding devices. Herein, the new encapsulation process, in-situ method, for CsPbBr3/TiO2 was presented to prevent the agglomeration of the particles and improve the stability of CsPbBr3 QDs without heat treatment at high temperature. The CsPbBr3 QDs were coated with TiO2 by using titanium tetraisopropoxide (TTIP) as a titanium source which was injected during the formation of CsPbBr3 QDs in which the effects of TTIP injection temperature from 25°C to 170°C were studied. The morphological, structural, and optical properties of CsPbBr3/TiO2 prepared by in-situ method were compared with ex-situ method reported in previous study. Besides preventing an aggregation, the in-situ TiO2 coated sample at 25°C exhibited the excellent stability against ambient air, non-polar solvent, water and visible light illumination owing to the protection of TiO2 deposited on the CsPbBr3 QDs surface and the good structure of CsPbBr3 QDs. Finally, the photoelectrochemical results showed that the in-situ coated sample at 100°C had the highest charge transport property among the others.