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Haralds Abolins1 Felix Deschler1

1, University of Cambridge, Cambridge, , United Kingdom

Ruddlesden-Popper perovskites have recently been shown possess greatly enhanced environmental and thermodynamic stability relative to their bulk counterparts, which has proven the key challenge for the commercialization of perovskite-based photovoltaics. Nevertheless, when these low-dimensionality materials are deposited in thin films through a fast crystallization process, a mixed phase material will result with bulk-like perovskite domains intermixed with grains of Ruddlesden-Popper perovskite of varying configurations in the number of atomic layers between each set of spacer cations. The precise composition will depend on processing conditions and will inevitably have an effect on the charge transport characteristics of the resulting material. While it has been shown that high-efficiency solar cells and LEDs can be fabricated from mixed dimensionality perovskites, the charge transport characteristics between the different phases in these materials have not been well understood. To elucidate the carrier dynamics in Ruddlesden-Popper perovskites a deposition procedure for obtaining thin films with micron-sized single-phase grains is developed. The spatial configuration of the various dimensionality phases is subsequently revealed through photoluminescence mapping and is shown to be tunable in both distribution and relative abundance by varying the deposition conditions. Lastly, it is demonstrated through spectrally resolved photoluminescence lifetime studies that charges are funnelled to the lowest band-gap phases of the materials through an energy transfer process that considerably increases local carrier concentration, leading to enhanced photoluminescence quantum efficiencies. Crucially, the geometry, rate and efficiency of this funnelling are shown to be tunable through only slight adjustments in processing conditions, allowing the energetic landscape to be tailored for individual applications.

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