An ultraviolet-ozone post-treatment to remove the inherent impurities in all-ambient solution-processed CsPbBr3perovskite films

Abstract

It is very important to exclude impurities during the material preparation process for the production of high-quality optoelectronic devices. For the all-ambient solution-processed CsPbBr3 films, unexpected inherent impurities could be inadvertently introduced, which would induce electronic trap states and impede carrier transport in the as-derived CsPbBr3-based optoelectronic devices, such as all-inorganic perovskite solar cells (PSCs). Herein, it is found that ultraviolet-ozone (UVO) post-treatment, which is usually applied for cleaning substrates, has the ability to remove these harmful impurities in all-ambient solution-processed CsPbBr3 films. Upon proper UVO post-treatment, the assembled PSC with the architecture of fluorine-doped tin oxide/compact TiO2 (c-TiO2)/CsPbBr3/carbon exhibits an improved power conversion efficiency of 7.82% from 7.37%. X-ray photoelectron spectroscopy measurements demonstrate that the undesirable inherent impurities in all-ambient solution-processed CsPbBr3 films may be related to organic solvents and adsorbates, which can be removed effectively by UVO post-treatment. After UVO post-treatment, photoluminescence and space-charge-limited current measurements reveal that CsPbBr3 films possess reduced trap states. Meanwhile, due to the enhanced contact between the CsPbBr3 film and the subsequently deposited carbon electrode, the charge collection at the interface is effectively promoted. Our work not only finds the influence of the inherent impurities residual in all-ambient solution process, but also proposes a simple and effective strategy to remove these impurities.