Hysteresis-less and stable perovskite solar cells with a self-assembled monolayer

Organic-inorganic halide perovskites are promising for use in solar cells because of their efficient solar power conversion. Current-voltage hysteresis and degradation under illumination are still issues that need to be solved for their future commercialization. However, why hysteresis and degradation occur in typical perovskite solar cell structures, with an electron transport layer of metal oxide such as SnO2, has not been well understood. Here we show that one reason for the hysteresis and degradation is because of the localization of positive ions caused by hydroxyl groups existing at the SnO2 surface. We deactivate these hydroxyl groups by treating the SnO2 surface with a self-assembled monolayer. With this surface treatment method, we demonstrate hysteresis-less and highly stable perovskite solar cells, with no degradation after 1000h of continuous illumination. Common issues facing perovskite solar cells are current-voltage hysteresis and degradation during illumination. Here, a self-assembled monolayer is applied to an SnO2 electron transport layer, helping to achieve hysteresis-less behavior and limited degradation after 1,000hours of illumination.