Pulsed-current electrodeposition of vertically aligned NiOx films for stable perovskite solar cells

Abstract

Inverted perovskite solar cells based on inorganic metal–oxide hole-transport layers (HTLs), such as nickel oxide (NiO_x), have attracted considerable research interest due to their excellent stability and low-cost fabrication. However, the widely used spin coating fabrication of inorganic HTLs is often challenged by the non-uniform aggregated morphologies and incompatibility with industrial manufacture process. Here, we demonstrate a pulsed-current electrodeposition strategy to fabricate well-organized NiO_x films that are composed of vertically aligned nanoflake networks. The periodic on–off electrical cycles upon electrodeposition allow the replenishment of ions at the electrode–solution interface and reduce the diffusion layer thickness, which results in nucleation and growth of the system in a well-controlled manner. The unique topography of the resulting NiO_x layer gives rise to an interlocked connection at the perovskite/HTL interface with strong interfacial adhesion and superior hole-extraction capability. More importantly, solar cells based on the NiO_x layer yield high power-conversion efficiencies over 25%, and maintain over 95% of their initial efficiency after operation at maximum power point under simulated AM 1.5G irradiation at 85 °C for 2130 hours.