Effect of film thickness and morphology on photoelectrochemical performance of (001) orientated BiOBr thin films prepared via mist CVD

Abstract

High-quality (001) orientated bismuth oxobromide (BiOBr) thin films were deposited on polycrystalline Sn: In2O3-glass substrates at open-air atmospheric pressure with mist chemical vapor deposition (CVD). Generally, it is difficult to control the surface morphology and thickness for BiOBr because of the high anisotropic crystal structure and very volatile halide. In this study, the growing thickness of BiOBr thin films showed a linear correlation with deposition time. Small thickness resulted in limited absorption ability, while large thickness led to increase of electrical resistance. The surface morphology of (001) orientated BiOBr thin films can be improved obviously under the acidic environment via suppressing Bi3+ hydrolysis. The (001) orientated BiOBr thin films that deposited by mixed solvent of DMF and 35% HNO3 aqueous solution exhibited the highest photocurrent density with 0.33 mA cm−2 at 0.6 V vs Ag/AgCl. The intermediate thickness and continuous surface morphology effectively promote the transfer and separation of electron-hole pairs, leading to superior photoelectrochemical (PEC) performance.