Real-Time Observation of Organic Cation Reorientation in Methylammonium Lead Iodide Perovskites
Bakker, Huib J
Rezus, Yves LA
Frost, Jarvist M
Jansen, Thomas LC
The Journal of Physical Chemistry Letters
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Bakulin, A., Selig, O., Bakker, H. J., Rezus, Y. L., Müller, C., Glaser, T., Lovrinic, R., et al. (2015). Real-Time Observation of Organic Cation Reorientation in Methylammonium Lead Iodide Perovskites. The Journal of Physical Chemistry Letters, 6 3663-3669. https://doi.org/10.1021/acs.jpclett.5b01555
The introduction of a mobile and polarized organic moiety as a cation in 3D lead-iodide perovskites brings fascinating optoelectronic properties to these materials. The extent and the time scales of the orientational mobility of the organic cation and the molecular mechanism behind its motion remain unclear, with different experimental and computational approaches providing very different qualitative and quantitative description of the molecular dynamics. Here we use ultrafast 2D vibrational spectroscopy of methylammonium (MA) lead iodide to directly resolve the rotation of the organic cations within the MAPbI3 lattice. Our results reveal two characteristic time constants of motion. Using ab initio molecular dynamics simulations, we identify these as a fast (∼300 fs) “wobbling-in-a-cone” motion around the crystal axis and a relatively slow (∼3 ps) jump-like reorientation of the molecular dipole with respect to the iodide lattice. The observed dynamics are essential for understanding the electronic properties of perovskite materials.
methylammonium lead iodide, molecular dynamics, ultrafast spectroscopy, vibrational spectroscopy, transient anisotropy
This work was supported by The Netherlands Organization for Scientific Research (NWO) through the “Stichting voor Fundamenteel Onderzoek der Materie” (FOM) research program. A.A.B. also acknowledges a VENI grant from the NWO. A.A.B. is currently a Royal Society University Research Fellow. Z.S. and Z.C. acknowledge the ANR-2011-JS09-004-01-PvCoNano project and the EU Marie Curie Career Integration Grant (303824). A.A.B., Z.S., and Z.C. thank Dutch-French Academy for the support through van Gogh grant.
External DOI: https://doi.org/10.1021/acs.jpclett.5b01555
This record's URL: https://www.repository.cam.ac.uk/handle/1810/250515