Ultrafast Carrier Diffusion in Perovskite Monocrystalline Films

Monocrystalline perovskite materials exhibit superior properties compared with polycrystalline perovskites, including lower defect density, minimal grain boundaries, and enhanced carrier mobility. Nevertheless, the preparation of large-area, high-quality single-crystal films, which could prove invaluable for photoelectronic applications, remains a significant challenge. The study of how their unique properties go beyond polycrystalline thin films is still missing. In our experiment, using polarization-selective transient absorption microscopy, we directly observed the spatial carrier transportation in methylammonium lead iodide (CH₃NH₃PbI₃, MAPbI₃) strip-shaped monocrystalline ultrathin films. Ultrafast carrier diffusion transportation was observed. The monocrystalline carrier diffusion coefficient D (∼22 cm² s^-1) is an order of magnitude higher than that in polycrystalline films. Anisotropic carrier diffusion of the MAPbI₃ single crystal has been discovered. It is also discovered that the electrons and holes are of different anisotropy and diffusion speed. This ultralong carrier transport inside the monocrystalline film provides solid support for the development of perovskite based photoelectronic devices.