Perovskite solar cells have emerged as a promising photovoltaic system with superb power conversion efficiency. For the practical application of the perovskite device, the greatest concern is the power output density and the related dynamics under the working conditions. In this study, the working conditions of the planar and mesoscopic perovskite solar cells are simulated and the power output density evolutions upon the working voltage are highlighted. The planar device exhibits higher capability in outputting power than the mesoscopic one. The transient photoelectric conversion dynamics are investigated under the open circuit, short circuit and working conditions. It is found that the power output and the dynamics processes are correlated intrinsically, which suggests that the power output is the competitive result of the charge carrier recombination and transport. The present work offers a unique view to elucidate the relationship between the power output and the charge carrier dynamics for the perovskite solar cells in a comprehensive manner, which would be beneficial to their future practical applications.

In addition, the hysteresis of perovskite solar cells has been a mystery, although researchers have proposed different hypotheses and done different experiments to verify. We have tried to introduce fullerene derivatives into the active layer of perovskite, and found that the hysteresis of the planar device has been greatly decreased. Furthermore, the density of trap states in the devices controlled by fullerene derivatives decreased significantly by time-resolved charge extraction experiments. In order to further explain the effect of the introduction of fullerene derivatives on perovskite films, we have also done a series of spectroscopic experiment of the intrinsic film. The spectra showed that the steady-state fluorescence spectra were blue-shifted (~6 nm) and the absorption spectra were almost unchanged. The temperature-dependent fluorescence results also confirm the blue shift of the spectra of the intrinsic perovskite films controlled by fullerenes, and the analysis of the spectra at low temperatures confirms that the introduction of fullerenes does passivation the defects. Therefore, this part of the work, through the time-resolved charge extraction and spectral experiments, reveals the origin of hysteresis.