Ultrafast Terahertz Probes of Charge Transfer and Recombination Pathway of CH$_{3}$NH$_{3}$PbI$_{3}$ Perovskites

We use transient terahertz photoconductivity measurements to demonstrate that upon optical excitation of CH3NH3PbI3 perovskite, the hole transfer from CH3NH3PbI3 into the organic hole-transporting material (HTM) Spiro-OMeTAD occurs on a sub-picosecond timescale. Second-order recombination is the dominant decay pathway at higher photo-excitation fluences as observed in neat CH3NH3PbI3 films. In contrast, under similar experimental conditions, second-order recombination weakly contributes the relatively slow recombination between the electrons in the perovskite and the injected holes in HTM, as a loss mechanism at the CH3NH3PbI3/Spiro-OMeTAD interface. Our results offer insights into the intrinsic photophysics of CH3NH3PbI3-based perovskites with direct implications for photovoltaic devices and optoelectronic applications.