  Perovskite-based solar cells are promising due to their rapidly improving
efficiencies, but suffer from instability issues. Recently it has been claimed
that one of the key contributors to the instability of perovskite solar cells
is ion migration induced electrode degradation, which can be avoided by
incorporating inorganic hole blocking layers (HBL) in the device architecture.
In this work, we investigate the operational environmental stability of
methylammonium lead iodide (MAPbI3) perovskite solar cells that contain either
an inorganic or organic HBL, with only the former effectively blocking ions
from migrating to the metal electrode. This is confirmed by X-ray photoemission
spectroscopy measured on electrodes of degraded devices, where only electrodes
of devices with an organic HBL show a significant iodine signal. Despite this,
we show that when these devices are degraded under realistic operational
conditions (i.e. constant illumination in a variety of atmospheric conditions),
both types of devices exhibit nearly identical degradation behavior. These
results demonstrate that contrary to prior suggestions, ion-induced electrode
degradation is not the dominant factor in perovskite environmental instability
under operational conditions.
