Inhibition of Iodide Ion Migration in Flexible Perovskite Solar Cells using Oxide–Metal–Oxide Transparent Electrode

Abstract Oxide–Metal (Ag)–Oxide films (OMO) are good candidates as flexible transparent electrodes for the perovskite solar cells (PSCs) because of their higher transmittance (∼86%), lower sheet resistance (∼7 Ω/sq), and superior bending property compared to those of the conventional indium tin oxide transparent electrodes. However, when OMO is used in PSCs, the iodide ions of the perovskite layer diffuse into the silver layer, resulting in the formation of AgI, an insulator. The formation of AgI lowers the conductivity of the OMO. As a result, the power conversion efficiency (PCE) and long-term driving stability of PSCs are decreased. To solve this problem, we introduced diethanolamine (DEA), known as an anti-corrosion additive, into the electron transport layer to prevent the binding between iodine and silver. To investigate the effect of DEA, we observed the change of sheet resistance of OMO films and photovoltaic performance of OMO-based PSCs according to DEA addition in SnO2. Furthermore, X-ray photoelectron spectroscopy was performed to confirm the formation and inhibition of AgI. We found that upon adding DEA, the PCE of PSCs increased to 11.3% and the operational stability improved from the existing 12 h to a maximum of 60 h, while maintaining more than 70% of the initial efficiency. Therefore, we think that the results of this study might suggest guidelines to use OMO transparent electrode for PSCs, and is helpful for the commercialization of PSCs.