▎ 摘　　要

In order to improve the inherently inefficient hole extraction from perovskite to carbon electrode in planar carbon-based perovskite solar cells (PSCs), herein, a novel composite electrode composed of single atom Ni doped graphene (Ni-NG) for PSCs is proposed for the first time. Ni-NG with low work function provides a great driving force to improve the hole extraction at the interface. Meanwhile, Ni-NG with abundant single-atom Ni active sites and large specific surface area can accelerate charge transport and strengthen interface contact. Optimized PSCs with composite electrode based on Ni-NG achieved a champion power conversion efficiency (PCE) of 12.39%, higher than PSCs with pristine carbon electrode and composite electrode based on NG. Our work exploits the application of single-atom Ni doped graphene as carbon electrode and provides new insights into the structure design of carbon electrode to obtain efficient planar carbon-based PSCs. (c) 2021 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).