Investigating Electron-Phonon Coupling in Formamidinium Lead Iodide Perovskite Using Ultrafast Laser Spectroscopy

Abstract

The high charge carrier mobilities of hybrid inorganic-organic lead halide perovskites has previously been linked to ferroelectric domain formation due to alignment of organic cations within films. [1], [2] Our two-dimensional infrared ultrafast spectroscopy studies reveal that organic cations re-orient within several picoseconds, and therefore ferroelectric domain formation is very unlikely and unable to account for the observed long carrier lifetimes.[3] Complimentary time-resolved infrared measurements examined the electron-phonon coupling in the conduction band. Analysis of the spectral line shapes indicates that carriers form polarons within the instrument response.