Aggregation State Regulation of Molecular Hole Conductors for Light‐Stable Perovskite Photovoltaics

Abstract The molecular aggregation state of organic hole conductors greatly influences charge collection of perovskite solar cells (PSCs). In this study, we optimize the core/periphery steric Cl‐substituent (W1, W2, W3) and regulate the aggregation state by molecular packing and interactions. It is demonstrated that W1 with Cl core‐substituent exhibits enhanced crystallization and strong intermolecular interactions in contrast to W2 with Cl sidechain‐substituent. Conversely, W3 with Cl substituent at both core and sidechain results in the most unfavorable molecular stacking. W1 exhibits high charge mobility and reinforced interfacial bonding, achieving a remarkable photovoltaic efficiency of 24.7%, outperforming the other two (W2's 23.9% and W3's 20.3%). Furthermore, W1‐ and W2‐PSCs retain 95.3% and 87.2% of their initial efficiency after 1,000 hours of maximum power point tracking (MPPT), respectively. This work provides fundamental insights into Cl‐substituent‐induced molecular aggregation behavior and offers a delicate approach for designing high‐performance organic hole semiconductors.