Deleterious Effect of Negative Capacitance on the Performance of Halide Perovskite Solar Cells

Negative capacitance in photovoltaic devices has been observed and reported in several cases, but its origin, at low or intermediate frequencies, is under debate. Here we unambiguously demonstrate a direct correlation between the observation of this capacitance and a corresponding decrease in performance of a halide perovskite (HaP; CsPbBr₃)-based device, expressed as reduction of open-circuit voltage and fill factor. We have prepared highly stable CsPbBr₃ HaPs that do not exhibit any degradation over the duration of the impedance spectroscopy measurements, ruling out degradation as the origin of the observed phenomena. Reconstruction of current–voltage curves from the impedance spectroscopy provided further evidence of the deleterious role of negative capacitance on photoconversion performance