“…Most of these defects are concentrated on the grain boundaries or surface of perovskite crystals and can lead to deep-level traps such as coordination-deficient Sn 2+ , coordination-deficient halide ions (I − or Br − ), Sn clusters, and Sn-I translocation. 3–5,29,30 In addition, some point defects that can form shallow traps, such as I or MA/FA vacancies, may also occur during film growth. The presence of these defect states severely affects the optoelectronic properties of Sn-based perovskite films.…”