Fluorescence spectroscopy-based study of balanced transport of charge carriers in hot-air-annealed perovskites.

Using fluorescence spectroscopy, we investigate the transport of charge carriers in (p-i-n) planar perovskite (CH3 NH3 PbI3-x Clx ) solar cells with the structure ITO/PEDOT:PSS/perovskites/PCBM/Ca/Al, in which the perovskite morphology is optimized by moisture pretreatment (MPT) and the hot-air-annealing process (HAAP). After annealing with hot air, the electron transport time of the perovskites is shortened by a factor of 3.6 (from 28.8 to 7.9 ns), eventually leading to balanced transport of electrons and holes (characterized by the fluorescence-decay time constants of 7.9 and 7.6 ns, respectively). These results are in good agreement with the observed increase in the photovoltaic conversion efficiency.