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Photodoping through local charge carrier accumulation in alloyed hybrid perovskites for highly efficient luminescence

Abstract

Metal halide perovskites have emerged as exceptional semiconductors for optoelectronic applications. Substitution of the monovalent cations has advanced luminescence yields and device efficiencies. Here, we control the cation alloying to enhance optoelectronic performance through alteration of the charge carrier dynamics in mixed-halide perovskites. In contrast to single-halide perovskites, we find high luminescence yields for photoexcited carrier densities far below solar illumination conditions. Using time-resolved spectroscopy we show that the charge carrier recombination regime changes from second to first order within the first tens of nanoseconds after excitation. Supported by microscale mapping of the optical bandgap, electrically gated transport measurements and first-principles calculations, we demonstrate that spatially varying energetic disorder in the electronic states causes local charge accumulation, creating p- and n-type photodoped regions, which unearths a strategy for efficient light emission at low charge-injection in solar cells and light-emitting diodes.

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Fig. 1: Charge carrier recombination dynamics.
Fig. 2: Temperature-dependent luminescence of mixed-halide MAFA films.
Fig. 3: Electrically gated measurements on charge transport and photoinduced doping in mixed-cation perovskites.
Fig. 4: DFT and TDDFT calculations reveal driving force for mixed-halide mediated charge separation.

Data availability

The data that support the plots within this paper and other findings of this study are available at the University of Cambridge Repository (https://doi.org/10.17863/CAM.43748).

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Acknowledgements

S.F. acknowledges funding from the Studienstiftung des deutschen Volkes and EPSRC, as well as support from the Winton Programme for the Physics of Sustainability. S.M. acknowledges funding from an EPSRC studentship. M.A.-J. thanks Nava Technology Limited, Cambridge Materials Limited and EPSRC (grant number: EP/M005143/1) for their funding and technical support. S.P.S. acknowledges funding from the Royal Society Newton Fellowship and EPSRC through a program grant (EP/M005143/1). T.A.S.D. acknowledges the National University of Ireland (NUI) for a Travelling Studentship and the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (HYPERION, grant agreement number 756962). K.F. acknowledges funding from a George and Lilian Schiff Foundation Studentship, an EPSRC studentship and a scholarship from the Winton Programme for the Physics of Sustainability. E.R. acknowledges funding from an ERC starting grant (no. 804523). R.H.F. acknowledges support from the Simons Foundation (grant 601946). Research work in Mons was supported by the Fonds de la Recherche Scientifique de Belgique - Fund for Scientific Research (F.R.S.-FNRS) and the EU Marie-Curie IEF project ‘DAEMON’. Computational resources have been provided by the Consortium des Équipements de Calcul Intensif (CÉCI). D.B. is an FNRS Research Director. S.D.S. acknowledges the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (HYPERION, grant agreement number 756962), the Royal Society and Tata Group (UF150033). F.D. acknowledges funding from the Winton Programme for the Physics of Sustainability. We would like to acknowledge the help of I. Buisman (Department of Earth Sciences, University of Cambridge) in assisting with EPMA data collection.

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Contributions

S.F., S.M., S.D.S. and F.D. conceived and planned the experiments with additional input from H.S., M.S., D.B. and R.H.F. J.P.H.R., S.M., M.A.-J. and K.F. fabricated the samples for spectroscopy measurements. S.F., S.M., J.P.H.R. and M.A.-J. performed the PLQE, TA and PL spectroscopy measurements. S.P.S. fabricated and measured the field-effect transistors with input from H.S. G.D.T. performed the confocal PL microscopy measurements. E.R., S.M. and T.A.S.D. prepared and performed EPMA measurements. G.N. and D.B. performed the DFT and TDDFT calculations. S.F. and F.D. drafted the manuscript and compiled figures, with discussion of results and feedback on the manuscript from all authors.

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Correspondence to Samuel D. Stranks or Felix Deschler.

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The authors declare the following competing financial interest: S.D.S. is a co-founder of Swift Solar Inc.

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Further film characterization, transient absorption and photoluminescence data, microscopy, transistor measurements and density-functional theory calculations.

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Feldmann, S., Macpherson, S., Senanayak, S.P. et al. Photodoping through local charge carrier accumulation in alloyed hybrid perovskites for highly efficient luminescence. Nat. Photonics 14, 123–128 (2020). https://doi.org/10.1038/s41566-019-0546-8

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