Fast Voltage Decay in Perovskite Solar Cells Caused by Depolarization of Perovskite Layer

The open-circuit voltage decay course in perovskite solar cells is studied in this work under the assistance of three techniques, i.e., electrochemical impedance spectroscopy, light intensity modulated photovoltage spectroscopy, and open-circuit voltage decay. In contrast to what is known in dye-sensitized solar cells, where V-oc decay is due to back transfer of electrons from the TiO2 conduction band to redox species in the electrolyte, we find that in perovskite solar cells, half of the voltage drop initially results from the fast depolarization of the perovskite layer. In other words, we observe that the polarization of perovskite film contributes to about half of the V-oc in the device. The loss of the other half of V-oc is found to be due to interfacial charge recombination.