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Issue 24, 2018
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Unraveling luminescence mechanisms in zero-dimensional halide perovskites

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Zero-dimensional (0D) halides perovskites, in which anionic metal-halide octahedra (MX6)4− are separated by organic or inorganic countercations, have recently shown promise as excellent luminescent materials. However, the origin of the photoluminescence (PL) and, in particular, the different photophysical properties in hybrid organic–inorganic and all inorganic halides are still poorly understood. In this work, first-principles calculations were performed to study the excitons and intrinsic defects in 0D hybrid organic–inorganic halides (C4N2H14X)4SnX6 (X = Br, I), which exhibit a high photoluminescence quantum efficiency (PLQE) at room temperature (RT), and also in the 0D inorganic halide Cs4PbBr6, which suffers from strong thermal quenching when T > 100 K. We show that the excitons in all three 0D halides are strongly bound and cannot be detrapped or dissociated at RT, which leads to immobile excitons in (C4N2H14X)4SnX6. However, the excitons in Cs4PbBr6 can still migrate by tunneling, enabled by the resonant transfer of excitation energy (Dexter energy transfer). The exciton migration in Cs4PbBr6 leads to a higher probability of trapping and nonradiative recombination at the intrinsic defects. We show that a large Stokes shift and the negligible electronic coupling between luminescent centers are important for suppressing exciton migration; thereby, enhancing the photoluminescence quantum efficiency. Our results also suggest that the frequently observed bright green emission in Cs4PbBr6 is not due to the exciton or defect-induced emission in Cs4PbBr6 but rather the result of exciton emission from CsPbBr3 inclusions trapped in Cs4PbBr6.

Graphical abstract: Unraveling luminescence mechanisms in zero-dimensional halide perovskites

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The article was received on 17 Mar 2018, accepted on 09 May 2018 and first published on 15 May 2018

Article type: Paper
DOI: 10.1039/C8TC01291A
Citation: J. Mater. Chem. C, 2018,6, 6398-6405
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    Unraveling luminescence mechanisms in zero-dimensional halide perovskites

    D. Han, H. Shi, W. Ming, C. Zhou, B. Ma, B. Saparov, Y. Ma, S. Chen and M. Du, J. Mater. Chem. C, 2018, 6, 6398
    DOI: 10.1039/C8TC01291A

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