Mechanism of Charge Transfer and Recombination Dynamics in Organo Metal Halide Perovskites and Organic Electrodes, PCBM, and Spiro-OMeTAD: Role of Dark Carriers.

Despite the unprecedented interest in organic–inorganic metal halide perovskite solar cells, quantitative information on the charge transfer dynamics into selective electrodes is still lacking. In this paper, we report the time scales and mechanisms of electron and hole injection and recombination dynamics at organic PCBM and Spiro-OMeTAD electrode interfaces. On the one hand, hole transfer is complete on the subpicosecond time scale in MAPbI3/Spiro-OMeTAD, and its recombination rate is similar to that in neat MAPbI3. This was found to be due to a high concentration of dark charges, i.e., holes brought about by unintentional p-type doping of MAPbI3. Hence, the total concentration of holes in the perovskite is hardly affected by optical excitation, which manifested as similar decay kinetics. On the other hand, the decay of the photoinduced conductivity in MAPbI3/PCBM is on the time scale of hundreds of picoseconds to several nanoseconds, due to electron injection into PCBM and electron–hole recombination a...