Vacuum-assisted thermal annealing of CsPbI${}_3$ for highly stable and efficient inorganic perovskite solar cells

Inorganic cesium lead iodide perovskite CsPbI${}_3$ is attracting great attention as a light absorber for single or multi-junction photovoltaics due to its outstanding thermal stability and proper band gap. However, the device performance of CsPbI${}_3$-based perovskite solar cells (PSCs) is limited by the unsatisfactory crystal quality and thus severe non-radiative recombination. Here, vacuum-assisted thermal annealing (VATA) is demonstrated as an effective approach for controlling the morphology and crystallinity of the CsPbI${}_3$ perovskite films formed from the precursors of PbI${}_2$, CsI, and dimethylammonium iodide (DMAI). By this method, a large-area and high-quality CsPbI${}_3$ film is obtained, exhibiting a much reduced trap-state density with prolonged charge lifetime. Consequently, the solar cell efficiency is raised from 17.26 to 20.06 %, along with enhanced stability. The VATA would be an effective approach for fabricating high-performance thin-film CsPbI${}_3$ perovskite optoelectronics. (© 2022 Wiley‐VCH GmbH)