Vacuum‐Assisted Thermal Annealing of CsPbI3for Highly Stable and Efficient Inorganic Perovskite Solar Cells

Abstract 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.