Mesoporous Electron-Selective Contacts Enhance the Tolerance to Interfacial Ion Accumulation in Perovskite Solar Cells

Perovskite-based solar cells are emerging as a potential new leading photovoltaic technology. However, several fundamental aspects of the stability remain unclear. In this Letter, we combine experimental measurements and numerical simulations to show that a mesoporous interface between the perovskite and the electron collection layer mitigates the reversible performance loss associated with the ion migration. We argue that larger interfacial area dilutes the concentration of defects that accumulate as a result of the ion migration within the perovskite under working conditions. Our investigation provides a quantitative description of the mechanism, identifying a critical defect concentration that devices can tolerate without reporting reduced performance.