Electron-acoustic phonon coupling in single crystal CH₃NH₃PbI₃ perovskites revealed by coherent acoustic phonons

Despite the great amount of attention CH₃NH₃PbI₃ has received for its solar cell application, intrinsic properties of this material are still largely unknown. Mobility of charges is a quintessential property in this aspect; however, there is still no clear understanding of electron transport, as reported values span over three orders of magnitude. Here we develop a method to measure the electron and hole deformation potentials using coherent acoustic phonons generated by femtosecond laser pulses. We apply this method to characterize a CH₃NH₃PbI₃ single crystal. We measure the acoustic phonon properties and characterize electron-acoustic phonon scattering. Then, using the deformation potential theory, we calculate the carrier intrinsic mobility and compare it to the reported experimental and theoretical values. Our results reveal high electron and hole mobilities of 2,800 and 9,400 cm² V^-1 s^-1, respectively. Comparison with literature values of mobility demonstrates the potential role played by polarons in charge transport in CH₃NH₃PbI₃.