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Rotational Dynamics of Organic Cations in the CH3NH3Pbl3 Perovskite



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


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.
Physical Chemistry Chemical Physics


Quasielastic neutron scattering, perovskites, solar cell


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 CH<sub>3</sub>NH<sub>3</sub>Pbl<sub>3</sub> Perovskite, Physical Chemistry Chemical Physics, [online], (Accessed July 25, 2024)


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Created December 13, 2015, Updated October 12, 2021