Unravelling the structural complexity and photophysical properties of adamantyl-based layered hybrid perovskites

Layered hybrid perovskites comprising adamantyl spacer (A) cations based on the A 2 FA n −1 Pb n I 3 n +1 ( n = 1-3, FA = formamidinium) compositions have recently been shown to act as promising materials for photovoltaic applications. While the corresponding perovskite solar cells show performances and stabilities that are superior in comparison to other layered two-dimensional formamidinium-based perovskite solar cells, the underlying reasons for their behaviour are not well understood. We provide a comprehensive investigation of the structural and photophysical properties of this unique class of materials, which is complemented by theoretical analysis via molecular dynamics simulations and density functional theory calculations. We demonstrate the formation of well-defined structures of lower compositional representatives based on n = 1-2 formulations with (1-adamantyl)methanammonium spacer moieties, whereas higher compositional representatives ( n > 2) are shown to consist of mixtures of low-dimensional phases evidenced by grazing incidence X-ray scattering. Furthermore, we reveal high photoconductivities of the corresponding hybrid perovskite materials, which is accompanied by long charge carrier lifetimes. This study thereby unravels features that are relevant for the performance of FA-based low-dimensional hybrid perovskites. Structural properties and photophysics of layered perovskites comprising adamantyl (A) cations in A 2 FA n −1 Pb n I 3 n +1 ( n = 1-3, FA = formamidinium) composition are studied by a combination of theoretical and experimental techniques to unravel unique features.