Spontaneous Enhancement of the Power Output in Surface-Passivated Triple-Cation Perovskite Solar Cells

The power conversion efficiency of hybrid organic-inorganic perovskite solar cells (PSCs) has been reported to increase spontaneously during storage in the dark and reaches its maximum sometimes only after several days. In most cases, an increased open-circuit voltage contributes to enhanced efficiency. This work investigates the role of surface passivation, in a form of 2D/3D perovskite heterostructures, at the hole extracting side of a triple-cation PSC in the spontaneous enhancement. Our observations demonstrate that spontaneous enhancement occurs for surface-passivated devices and therefore rule out surface passivation mechanisms initiating the spontaneous enhancement.