The dynamics of methylammonium ions in hybrid organic–inorganic perovskite solar cells

Aurelien M. A. Leguy, Jarvist Moore Frost, Andrew P. Mcmahon, Victoria Garcia Sakai, W. Kochelmann, Chunhung Law, Xiaoe Li, Fabrizia Foglia, Aron Walsh, Brian C. O’regan, Jenny Nelson, João T. Cabral, Piers R. F. Barnes

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Abstract

Methylammonium lead iodide perovskite can make high-efficiency solar cells, which also show an unexplained photocurrent hysteresis dependent on the device-poling history. Here we report quasielastic neutron scattering measurements showing that dipolar CH3NH3+ ions reorientate between the faces, corners or edges of the pseudo-cubic lattice cages in CH3NH3PbI3 crystals with a room temperature residence time of ∼14 ps. Free rotation, π-flips and ionic diffusion are ruled out within a 1–200-ps time window. Monte Carlo simulations of interacting CH3NH3+ dipoles realigning within a 3D lattice suggest that the scattering measurements may be explained by the stabilization of CH3NH3+ in either antiferroelectric or ferroelectric domains. Collective realignment of CH3NH3+ to screen a device’s built-in potential could reduce photovoltaic performance. However, we estimate the timescale for a domain wall to traverse a typical device to be ∼0.1–1 ms, faster than most observed hysteresis.
Original languageEnglish
Article number7124
Pages (from-to)1-10
Number of pages10
JournalNature Communications
Volume6
DOIs
Publication statusPublished - 29 May 2015

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