The Nature of Electron Mobility in Hybrid Perovskite CH₃NH₃PbI₃

CH₃NH₃PbI₃ is one of the most promising candidates for cheap and high-efficiency solar cells. One of its unique features is the long carrier diffusion length (>100 μm), but its carrier mobility is rather modest. The nature of the mobility is unclear. Here, using nonadiabatic wave function dynamics simulations, we show that the random rotations of the CH₃NH₃ cations play an important role in the carrier mobility. Our previous work showed that the electron and hole wave functions were localized and spatially separated due to the random orientations of the CH₃NH₃ cations in the tetragonal phase. We find that the localized carriers are able to conduct random walks due to the electrostatic potential fluctuation caused by the CH₃NH₃ random rotations. The calculated electron mobilities are in the experimentally measured range. We thus conclude that the carrier mobility of CH₃NH₃PbI₃ is likely driven by the dynamic disorder that causes the fluctuation of the electrostatic potential.