Multifunctional Core-Substituted <i>N</i>-Phenylaniline for Linear Hole-Transport Materials Enabling Durable Perovskite Solar Cells

Linear small-molecule hole-transporting materials (HTMs) exhibit distinctive advantages such as enhanced π-stacking and high hole mobility. However, they often face challenges, including molecular aggregation and poor film-forming properties. In this study, we propose a molecular engineering strategy for linear HTMs through the introduction of a core-substituted multifunctional group, N-diphenylamine (DPA), which effectively mitigates molecular aggregation and improves film formation by increasing the intermolecular distance due to its steric hindrance. Moreover, the DPA moiety provides additional hole-transport sites that facilitate hole transfer, thereby further enhancing the hole mobility of FR01. According to DFT calculations, the core-substituted DPA unit in FR01 strengthens interfacial interactions by forming direct O···Pb2+ bonds between its methoxy group and the perovskite surface, which promotes efficient hole extraction and suppresses charge recombination. As a result, FR01-based perovskite solar cells achieved a power conversion efficiency (PCE) of up to 22.77%, along with excellent long-term stability (retaining 89% of the initial PCE after 1000 h). This work highlights the potential of core-substituted DPA moieties in addressing critical limitations of linear HTMs and offers a promising multifunctional semiconductor design platform for future advancements in high-performance perovskite photovoltaics.