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.

有机-无机杂化金属卤化物钙钛矿（Hybrid organic-inorganic metal halide perovskites，HOIPs）是一类具有高效太阳能吸收剂应用潜力的材料。这类材料可通过在A位引入小有机阳离子进行合成，而这会显著影响其晶格动力学特性。目前，尚未有关于光学声子色散的公开报道——该色散现象被认为会因“热声子瓶颈”（hot phonon bottleneck）的形成而影响载流子热化过程。理论研究表明，光学声子会失去其波矢依赖性，转变为扩散子（diffusons）。我们计划利用MERLIN仪器的多重复频率功能，以高能量分辨率绘制甲基铵碘化铅（methylammonium lead iodide）中的声学声子与光学声子图谱。这将有助于阐明光学声子的特性及其对光电性能的影响。