Synergistic Graphene Polishing Enabling van der Waals Anchors for Efficient and Robust Carbon-Based Perovskite Solar Cells.

Carbon-based perovskite solar cells (C-PSCs) offer a low-cost, stable alternative to metal electrodes; however, the high porosity of carbon electrodes leads to poor interfacial contact and weak mechanical adhesion to the underlying carrier transport layer, limiting device performance and robustness. Here, we report a solvent-free additive polishing strategy using a synergistic combination of two-dimensional (2D) graphene nanoplatelets and 3D graphite flakes to densify the hole-transport-layer (HTL)/carbon interface by creating conformal van der Waals (vdW) anchors. This graphene/graphite additive polishing process fills micro-voids on the porous carbon electrode surface, reduces carbon electrode surface roughness, and creates a graphene anchor that increases interfacial fracture energy and promotes the carbon surface heating release. Electrically, the polished interface facilitates superior charge extraction, thereby reducing charge-transfer resistance. Consequently, regular n-i-p perovskite solar devices achieve a promised power conversion efficiency (PCE) of 23.28% (0.09 cm2) and maintain a high PCE of 19.62% at a scalable 1.0 cm2 area. This work provides a high-throughput, dry-processing paradigm for more affordable, robust, and highly efficient carbon-based perovskite photovoltaics.