  Negative capacitance at the low-frequency domain and inverted hysteresis are
familiar features in perovskite solar cells, where the origin is still under
discussion. Here we use Impedance Spectroscopy to analyse these responses in
methylammonium lead bromide cells treated with lithium cation at the electron
selective layer/perovskite interface and in iodide devices exposed to different
relative humidity conditions. Employing the Surface Polarization Model, we
obtain a time constant associated to the kinetics of the interaction of
ions/vacancies with the surface, {\tau}kin, in the range of 10^0 - 10^2 s for
all the cases exhibiting both features. These interactions lead to a decrease
in the overall recombination resistance, modifying the low-frequency perovskite
response and yielding to a flattening of the cyclic voltammetry. As consequence
of these results we find that that negative capacitance and inverted hysteresis
lead to a decrease in the fill factor and photovoltage values.
