Charge carrier localised in zero-dimensional (CH3NH3)3Bi2I9 clusters

Ni, Chengsheng and Hedley, Gordon J. and Payne, Julia and Svrcek, Vladimir and McDonald, Calum and Jagadamma, Lethy Krishnan and Edwards, Paul and Martin, Robert and Jain, Gunisha and Carolan, Darragh and Mariotti, Davide and Maguire, Paul and Samuel, Ifor and Irvine, John (2017) Charge carrier localised in zero-dimensional (CH3NH3)3Bi2I9 clusters. Nature Communications, 8. 170. ISSN 2041-1723

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    Abstract

    A metal-organic hybrid perovskite with 3-D framework of metal halide octahedra has been reported as a low-cost, solution processable absorber for a thin film solar cell with a power conversion efficiency over 20 %. Low-dimensional layered perovskites with metal halide slabs separated by the insulating organic layers are reported to show higher stability, but the efficiencies of the solar cells are limited by the anisotropy of the crystals because of the confinement of excitons. In order to explore the confinement and transport of excitons in zero-dimensional metal-organic hybrid materials, a highly-orientated film of methylammonium bismuth halide, (CH3NH3)3Bi2I9, with a nanometer sized core cluster of Bi2I93- surrounded by insulating CH3NH3+, was deposited on a quartz substrate via solution processing. The (CH3NH3)3Bi2I9 film shows highly anisotropic photoluminescence emission and excitation due to the large proportion of localized excitons coupled with a small number of delocalised excitons from inter-cluster energy transfer. The abrupt increase in photoluminescence quantum yield at excitation energy above twice band gap could indicate a quantum cutting due to the low dimensionality.