Effect of UV Exposure on IV Characteristics of a Perovskite Solar Cell

We report on the performance evolution of a perovskite solar cell under constant ultraviolet (UV) illumination measured by current-voltage scans and wide-field photoluminescence (PL) hyperspectral imaging. We observed a significant decrease in the PL intensity corresponding to a reduction in the quasi-Fermi level splitting energy after 218 hours of UV exposure. The evolving current-voltage characteristics show a constant reduction in the cell's power conversion efficiency dominated by a decrease in the fill factor, although both the open circuit voltage and the short circuit current also degrade modestly. The current-voltage measurements show a shift from a conventional hysteresis behavior to inverted hysteresis following the UV exposure of the device. The traditional double-diode model was not sufficient for accurately explaining the current density-voltage curves, so an extension to the model was necessary. The modified resistance-limited enhanced recombination model explains all the features of the current-voltage data with good accuracy. This work suggests the emergence of an additional recombination region in the cell, possibly an energetic barrier at the interface of the perovskite and the hole transport layer upon UV exposure.