Hybrid Central Substitution of Acceptor Boosts Efficient Near-Infrared Organic Photovoltaics

Abstract

Near-infrared (NIR) organic photovoltaic molecules are usually restricted by the “energy-gap-law”, thus rendering it greatly challenging to achieve organic solar cells (OSCs) with large open-circuit voltages (VOC) and NIR absorptions simultaneously. Herein, a synergistic strategy of hybrid central substitution on acceptors is developed, with electron-donating methyl/methoxy achieving NIR absorptions while electron-withdrawing bromine inducing favorable molecular packings. A single crystal analysis reveals the rarely observed OC-H∙∙∙S non-covalent interaction and potentially beneficial entanglement of alkyl chains in CH29 with central methoxy. Consequently, the OSC of CH29 reaches both the excellent VOC of 884 mV and short-circuit current density of 28.30 mA/cm2 under a quite narrow optical bandgap of ~1.33 eV, meanwhile, almost the smallest energy loss in high-performance OSC systems. Our successful attempt at hybrid central substitution provides a feasible pathway to construct high-performance NIR acceptors, essential to record-breaking OSCs, especially for rear cells of tandem devices that require high VOC and broad photoelectric response simultaneously.