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Issue 35, 2019
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Intrinsic doping limit and defect-assisted luminescence in Cs4PbBr6

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Cs4PbBr6 is a member of the extended halide perovskite family that is built from isolated (zero-dimensional) PbBr64− octahedra with Cs+ counter ions. The material exhibits anomalous optoelectronic properties: optical absorption and weak emission in the deep ultraviolet (310–375 nm) with efficient luminescence in the green region (∼540 nm). Several hypotheses have been proposed to explain the giant Stokes shift including: (i) phase impurities; (ii) self-trapped exciton; (iii) defect emission. We explore, using first-principles theory and self-consistent Fermi level analysis, the unusual defect chemistry and physics of Cs4PbBr6. We find a heavily compensated system where the room-temperature carrier concentrations (<109 cm−3) are more than one million times lower than the defect concentrations. We show that the low-energy Br-on-Cs antisite results in the formation of a polybromide (Br3) species that can exist in a range of charge states. We further demonstrate from excited-state calculations that tribromide moieties are photoresponsive and can contribute to the observed green luminescence. Photoactivity of polyhalide molecules is expected to be present in other halide perovskite-related compounds where they can influence light absorption and emission.

Graphical abstract: Intrinsic doping limit and defect-assisted luminescence in Cs4PbBr6

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Article information

26 Jun 2019
13 Aug 2019
First published
14 Aug 2019

J. Mater. Chem. A, 2019,7, 20254-20261
Article type

Intrinsic doping limit and defect-assisted luminescence in Cs4PbBr6

Y. Jung, J. Calbo, J. Park, L. D. Whalley, S. Kim and A. Walsh, J. Mater. Chem. A, 2019, 7, 20254
DOI: 10.1039/C9TA06874K

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