Real-time view of liquid-like screening and large polaron formation in lead halide perovskites

Because of their exceptional performance and ease of production, hybrid organic-inorganic perovskites are excellent candidate materials for next-generation solar cells. Despite static and dynamic disorder, lead-halide based perovskites demonstrate remarkable optoelectronic properties that rival those of defect-free semiconductors. This unusual defect tolerance is responsible for several properties that make these perovskites promising next-generation solar cell materials, including long carrier lifetimes, long diffusion lengths, and low electron-hole recombination rates. These observations are consistent with a large polaron shielding model, in which dynamic screening of charge carriers minimizes scattering with longitudinal optical phonons, charged defects, and other charges [1]. In addition, the large polaron model also explains the presence of long-lived hot electrons observed in two-photon photoemission experiments of CH
3
NH
3
PbI
3
thin films and time-resolved photoluminescence measurements of CH
3
NH
3
PbBr
3
single crystals [2,3].