Reciprocal space imaging of acoustic and optical phonons in methylammonium lead iodide

Hybrid organic-inorganic metal halide perovskites (HOIPs) are a class of materials that have potential use as high-efficiency solar absorbers. These materials can be synthesized with a small organic cation on the A site; greatly affecting the lattice dynamics. Currently, there are no published dispersions of the optical phonons, which have been proposed to affect carrier thermalization due to formation of a "hot phonon bottleneck". Theoretical studies have proposed that the optical phonons lose their wavevector dependence to become diffusons. We propose to use the multi-rep rate option of the MERLIN instrument to map out the acoustic and optical phonons in methylammonium lead iodide with high energy resolution. This will help elucidate the character of the optical phonons and their effect on optoelectronic properties.