Pressure-induced phase transition in methylammonium lead iodide

One key to the famous and remarkable photovoltaic properties of methylammonium lead iodide is its structural flexibility. This flexibility can be characterised by testing the structural response to applied pressure. We have previously performed an experiment on PEARL in which we demonstrated the existence of a new low-symmetry phase above about 0.3 GPa. This phase does not correspond to any known unit cell, but unfortunately the PEARL resolution was not sufficient to index it from scratch. For this reason, in this rapid access proposal we propose to measure this phase in a gas cell on GEM, taking advantage of the smaller background and higher resolution especially of the backscattering bank to characterise this new structure. Our results will be of significant interest to the very large hybrid halide perovskite community, and will form part of the PhD thesis of one of the proposers (JL).