High-quality and full-coverage CsPbBr3 thin films via electron beam evaporation with post-annealing treatment for all-inorganic perovskite solar cells

Abstract

Due to their superior stability in comparison to organic–inorganic hybrid devices, all-inorganic cesium lead bromide (CsPbBr3) perovskite solar cells (PSCs) have garnered considerable attention. However, the conventional solution process is limited for the preparing of CsPbBr3 films due to the limitation of bromide in solution, resulting in uneven film and low coverage. So, the development of viable evaporation deposition strategies is essential for boosting the power conversion efficiency (PCE) of CsPbBr3-based PSCs. In this work, high-quality and full-coverage CsPbBr3 thin films are fabricated using single-source electron beam evaporation followed with post-annealing treatment. Br-rich condition in evaporation process is realized by using the mixture of CsPbBr3 and Cs4PbBr6 powders as source materials, and the formation of CsPb2Br5 phase is successfully suppressed. Furthermore, the influences of annealing temperature and annealing time on the crystallinity, morphology and optical properties of the films are thoroughly explored. High-quality CsPbBr3 films with good uniformity and crystallinity are achieved by systematic optimization of the annealing parameters. As a result, a device efficiency of 7.81% with an open circuit voltage (VOC) of 1.43 V has been achieved for the PSCs with a planar structure of FTO/c-TiO2/CsPbBr3/carbon.