Dynamics and local ordering in formamidinium based organic-inorganic hybrid perovskites; A parametric study

The interest in organic-inorganic hybrid perovskites has boomed in recent years riding off the back of the recent push beyond the 22% efficiency mark. The novelty of the system hinges upon the inclusion of an organic cation as the “A” unit of the prototypical ABX3 perovskite structure. We wish to study a series of formamidinium (FA) based variants which has received surprisingly little attention, despite initial studies showing a more complex phase behaviour, with a metastable phase at high temperature. We will employ a combined INS and ab initio approach to understand the atomistic dynamics, bonding and local ordering. We seek to explain the observed differences in phase behaviour and dielectric properties at the atomic scale, with the hope of uncovering general design principles to tailor phase behaviour and dynamics.