The effect of caesium alloying on the ultrafast structural dynamics of hybrid organic–inorganic halide perovskites
Nathaniel P. Gallop, Junzhi Ye, Gregory M. Greetham, Thomas L. C. Jansen, Linjie Dai, Szymon J. Zelewski, Rakesh Arul, Jeremy J. Baumberg, Robert L. Z. Hoye, Artem A. Bakulin
Abstract
. We find that caesium incorporation primarily inhibits the slower 'reorientational jump' modes of the organic cation, whilst a smaller effect on the fast 'wobbling time' may be due to distortions and rigidisation of the inorganic cuboctahedral cage. 2DIR centre-line-slope analysis further reveals that while static disorder increases with caesium substitution, the dynamic disorder (reflected in the phase memory of the N-H stretching mode of methylammonium) is largely independent of caesium addition. Our results contribute to the development of a unified model of cation dynamics within organohalide perovskites.