Role of the monovalent cation on the self-doping of tin halide perovskites

The role of A-site cations (MA⁺, FA⁺, Cs⁺) is well-studied in lead halide perovskites, while it is less explored in tin perovskites. Here, we process tin-triiodide perovskite thin films with different A-site cations and we investigate their influence on the formation energy of Sn vacancy defects and thus on the self-doping of the semiconductor. To do so, we carefully take into account the morphology, crystallinity and optoelectronic properties of tin-based perovskite thin films in order to distinguish between the intrinsic properties of the semiconductor related to its chemical composition and those induced by the strong structure-processing-property relationship of these materials. Combining structural and electrical characterization with DFT calculations we show that there is a minimal modulation of the electronic and defect chemistry depending on the different A-site cations. This study emphasizes the critical role of film quality in determining electronic properties and provides insights for improving tin perovskite solar cell performance.