Efficient Regular Perovskite Solar Cells Based on Pristine [70]Fullerene as Electron‐Selective Contact

Abstract [70]Fullerene is presented as an efficient alternative electron‐selective contact (ESC) for regular‐architecture perovskite solar cells (PSCs). A smart and simple, well‐described solution processing protocol for the preparation of [70]‐ and [60]fullerene‐based solar cells, namely the fullerene saturation approach (FSA), allowed us to obtain similar power conversion efficiencies for both fullerene materials (i.e., 10.4 and 11.4 % for [70]‐ and [60]fullerene‐based devices, respectively). Importantly, despite the low electron mobility and significant visible‐light absorption of [70]fullerene, the presented protocol allows the employment of [70]fullerene as an efficient ESC. The [70]fullerene film thickness and its solubility in the perovskite processing solutions are crucial parameters, which can be controlled by the use of this simple solution processing protocol. The damage to the [70]fullerene film through dissolution during the perovskite deposition is avoided through the saturation of the perovskite processing solution with [70]fullerene. Additionally, this fullerene‐saturation strategy improves the performance of the perovskite film significantly and enhances the power conversion efficiency of solar cells based on different ESCs (i.e., [60]fullerene, [70]fullerene, and TiO 2 ). Therefore, this universal solution processing protocol widens the opportunities for the further development of PSCs.