Phonon-Electron Scattering Limits Free Charge Mobility in Methylammonium Lead Iodide Perovskites

The nature of the photoconductivity in solution-processed films of methylammonium lead iodide perovskite is investigated by determining the variation of the photoconductive response with temperature. Ultrabroadband terahertz (THz) photoconductivity spectra in the 0.3-10 THz range can be reproduced well by a simple Drude-like response at room temperature, where free charge carrier motion is characterized by an average scattering time. The scattering time determined from Drude fits in the 0.3-2THz region increases from similar to 4 fs at 300 K (tetragonal phase; mobility of similar to 27 cm(2) V-1 s(-1)) to almost similar to 25 fs at 77 K (orthorhombic phase, mobility of similar to 150 cm(2) V-1 s-'). For the tetragonal phase (temperature range 150 < T < 300 K) the scattering time shows a,similar to,T-3/2 dependence, approaching the theoretical limit for pure acoustic phonon (deformation potential) scattering. Hence, electron-phonon, rather than impurity scattering, sets the upper limit on free charge transport for this perovskite.