Dresden 2017 – wissenschaftliches Programm
CPP 20.7: Vortrag
Dienstag, 21. März 2017, 11:30–11:45, ZEU 222
Exploring the electronic band structure of (organo-)metal halide perovskite via photoluminescence anisotropy of individual nanocrystals — •Daniela Täuber1, Mirko Goldmann1,2, Juanzi Shi1, Alexander Dobrovolsky1, and Ivan Scheblykin1 — 1Chemical Physics, Lund University, Lund, Sweden — 2TU Ilmenau, Germany
Understanding electronic processes in metal halide perovskites requires unraveling the origin of their electronic transitions. Light polarization studies can provide important information regarding transition dipole moment orientations. Investigating individual lead trihalide perovskite nanocrystals enabled us to detect the polarization of photoluminescence intensity and photoluminescence excitation, hidden in bulk samples by ensemble averaging. Polarization properties of CH3NH3PbI3 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.
D.T. acknowledges a personal research grant DFG-TA 1049/1-1.
 Täuber, D. et al., Nano Letters 16, 5087-5094, 2016.