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

Abstract

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 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 to improve tin perovskite solar cell performance.