Disordered vibrational phenomena in triple cation 3D perovskites

Halide perovskites are of great interest as materials for next generation solar power and other semi-conductor uses. The
present direction of research is moving away from "standard" formulations of halide perovskites to more "exotic"
materials. We have interest in a "triple-cation" formulation containing a mixture of FA, MA, and Cs as the cation. For their
inclusion into devices the thermal, and hence vibrational, properties are of crucial importance. We have started our study
by looking at the surface vibrational modes using helium-3 spin echo. We would like to extend the study to the bulk
vibrational modes. The current proposal is to study the samples in powder form to supplement the helium-3 spin echo
measurements, and provide a test case for potential future measurements on single crystal samples. We have two
samples, the triple Cation FA0.85MA0.1Cs0.05Pb(I0.85Br0.15)3, and then also the more conventional FAPbBr3 for
comparison.