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Local Energy Landscape Drives Long-Range Exciton Diffusion in Two-Dimensional Halide Perovskite Semiconductors.

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Baldwin, Alan 
Chahbazian, Rosemonde 
Galkowski, Krzysztof  ORCID logo


Halide perovskites are versatile semiconductors with applications including photovoltaics and light-emitting devices, having modular optoelectronic properties realizable through composition and dimensionality tuning. Layered Ruddlesden-Popper perovskites are particularly interesting due to their unique 2D character and charge carrier dynamics. However, long-range energy transport through exciton diffusion in these materials is not understood or realized. Here, local time-resolved luminescence mapping techniques are employed to visualize exciton transport in exfoliated flakes of the BA2MAn-1PbnI3n+1 perovskite family. Two distinct transport regimes are uncovered, depending on the temperature range. Above 100 K, diffusion is mediated by thermally activated hopping processes between localized states. At lower temperatures, a nonuniform energy landscape emerges in which transport is dominated by downhill energy transfer to lower-energy states, leading to long-range transport over hundreds of nanometers. Efficient, long-range, and switchable downhill transfer offers exciting possibilities for controlled directional long-range transport in these 2D materials for new applications.



3403 Macromolecular and Materials Chemistry, 34 Chemical Sciences, 3406 Physical Chemistry, 7 Affordable and Clean Energy

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J Phys Chem Lett

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American Chemical Society (ACS)
European Research Council (756962)
Engineering and Physical Sciences Research Council (EP/R023980/1)
Royal Society (UF150033)
Royal Society (NF170533)
The authors acknowledge the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (HYPERION, Grant Agreement Number 756962). SDS acknowledges funding from the Royal Society and Tata Group (UF150033). GD acknowledges the Royal Society for funding through a Newton International Fellowship. GD and SDS acknowledge the UK Engineering and Physical Sciences Research Council (EPSRC) under grant reference EP/R023980/1. A.B. acknowledges a Robert Gardiner Scholarship and funding from Christ’s College, Cambridge. K.G. acknowledges support from the Polish Ministry of Science and Higher Education within the Mobilnosc Plus program (GrantNo.1603/MOB/V/2017/0). The authors thank Niall Goulding and Rachel Bothwell for valuable discussions.

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