Mechanism Investigation of the Synergistically Enhanced Performance of Carbon-Based Perovskite Solar Cells Utilizing Coal-Derived Multilayer Graphene with NiO_<i>x</i>

The efficiency of carbon-based perovskite solar cells (C-PSCs) still significantly lags behind that of metal-based devices due to the substantial interfacial resistance and energy level mismatch between the carbon electrodes (CE) and the perovskite material. Herein, we present the construction of a carrier highway utilizing coal-derived multilayered graphene (MG) embedded with NiO_<i>x</i> as a hole-transport layer (HTL). This approach aims to optimize energy level alignment and enhance interfacial contact, thereby improving the quality of the perovskite film. Due to its unique multilayer structure and abundant oxygen-containing functional groups, coal-derived MG synergized with NiO_<i>x</i> HTL not only provides well-aligned energy band configurations that facilitate charge separation and extraction but also acts as a Lewis base to form coordination bonds with uncoordinated lead ions by sharing electron pairs, thereby reducing surface defects and minimizing recombination losses at the perovskite/CE interface, ultimately alleviating fill factor (FF) loss. As a result, the power conversion efficiency (PCE) of the FTO/SnO₂/MAPbI₃/MG + NiO_<i>x</i>/Carbon structured device achieved 18.10%, representing a significant enhancement of 19.3% compared to that of 15.17% for the pristine device. This study presents a novel strategy for enhancing the overall performance of C-PSCs through the utilization of cost-effective and environmentally sustainable carbon functional materials derived from coal.