期刊
NANO LETTERS
卷 16, 期 8, 页码 5087-5094出版社
AMER CHEMICAL SOC
DOI: 10.1021/acs.nanolett.6b02012
关键词
organometal halide perovskite; photoluminescence polarization; individual nanocrystal; band structure; trap-assisted emission; fluorescence microscopy
类别
资金
- German Research Foundation [DFG-Ta 1049/1-1]
- Crafoord foundation
- Knut & Alice Wallenberg foundation
- Swedish Research Council
Understanding electronic processes in organometal halide perovskites, flourishing photovoltaic, and emitting materials requires unraveling the origin of their electronic transitions. Light polarization studies can provide important information regarding transition dipole moment orientations. Investigating individual methylammonium lead triiodide perovskite nanocrystals enabled us to detect the polarization of photoluminescence intensity and photoluminescence excitation, hidden in bulk samples by ensemble averaging. Polarization properties of the crystals were correlated with their photoluminescence spectra and electron microscopy images. We propose that distortion of PbI6 octahedra leads to peculiarities of the electronic band structure close to the band-edge. Namely, the lowest band transition possesses a transition dipole moment along the apical Pb-I-Pb bond resulting in polarized photoluminescence. Excitation of photoluminescence above the bandgap is unpolarized because it involves molecular orbitals delocalized both in the apical and equatorial directions of the perovskite octahedron. Trap-assisted emission at 77 K, rather surprisingly, was polarized similar to the bandgap emission.
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