The effect of guanidinium tetrafluoroborate surface passivation on the stability of 2D-PEA2SnI4 perovskite thin films prepared by sequential physical vapor deposition

2D-PEA₂SnI₄ perovskites thin films were prepared by sequential physical vapor deposition (SPVD), and passivated in vacuum using guanidinium tetrafluoroborate (GuaBF₄). The effect of GuaBF₄ on stability, optical, morphological, electrical, and structural properties of PEA₂SnI₄ films was investigated. The introduction of GuaBF₄ improved the film morphology and crystallinity with the resulting films exhibiting enlarged grain sizes and low surface roughness. Raman and FTIR results showed that GuaBF₄ did not change the structural phase and the functional group of the perovskite, but rather confirmed an additive-perovskite interaction. PL and carrier lifetime measurements revealed a 1.8 and 2-folds increment in intensity and lifetime respectively, attributed to suppression of non-radiative recombination in GuaBF₄ treated films. XRD, UV–Vis and FE-SEM stability studies showed that GuaBF₄ treatment significantly improved the stability of the films. This study suggests an effective strategy for deposition of solvent-free additive based 2D-Sn perovskite high quality films that are stable and reproducible.