Rotational Dynamics of Organic Cations in the CH3NH3Pbl3 Perovskite

Published

December 14, 2015

Author(s)

Tianran Chen, Benjamin J. Foley, Bahar NMN Ipek, Madhu Sudan Tyagi, John R. Copley, Craig Brown, Joshua J. Choi, Seunghun Lee Lee

Abstract

All semiconductors can generate free charges by absorbing light. However, not all semiconductors are high performance photovoltaic materials, because the charge carriers with opposite signs, electrons and holes, quickly annihilate each other. High photovoltaic effects arise when the charge recombination is slow and the charge carriers have high mobility. Methylammonium lead iodide (CH₃NH₃PBI₃) exhibits these favorable properties. Here, using neutron scattering techniques and group theoretical analysis, we identify a rotational mode of the CH₃NH₃⁺ cation with a characteristic relaxation of 5 ps at room temperature that is intimately linked to the photovoltaic effects. Temperature dependence of the relaxation rate indicates that the four-fold rotation of the C-N axis and the associated dipole plays a central role in controlling the dielectric constant, exciton binding energy and charge recombination rate that ultimately determine the solar cell performance.

Citation

Physical Chemistry Chemical Physics

Volume

17

Issue

46

Pub Type

Journals

Download Paper

Local Download

Keywords

Quasielastic neutron scattering, perovskites, solar cell

Citation

Chen, T. , Foley, B. , Ipek, B. , Tyagi, M. , Copley, J. , Brown, C. , Choi, J. and Lee, S. (2015), Rotational Dynamics of Organic Cations in the CH₃NH₃Pbl₃ Perovskite, Physical Chemistry Chemical Physics, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=918755 (Accessed October 30, 2025)