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 (NiOx), 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 NiOx 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 NiOx 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 NiOx layer yield high powerconversion 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.