Electrostatic Interaction-Mediated Enhancement of Charge Transfer Under Low Voltage Loss in A-D-A-Type Nonfullerene Acceptors

Acceptor-donor-acceptor (A-D-A)-type nonfullerene acceptors (NFAs) have driven key efficiency advances in organic solar cells (OSCs). However, progress in these systems has recently stalled due to the lack of an effective design strategy that enables efficient charge transfer without incurring excessive voltage loss. Here, we demonstrate that intermolecular electrostatic interactions can be exploited to regulate acceptor energy levels and thereby enhance charge-transfer efficiency under low voltage loss. By incorporating a fluoroalkyl-substituted analogue (MC7F3) into the M-series acceptor M36, the hole-transfer driving force is selectively increased without appreciable perturbation of the lowest unoccupied molecular orbital energy level. Meanwhile, the presence of MC7F3 promotes tighter intermolecular π-π stacking and a more favorable vertical phase distribution, which together facilitate efficient exciton dissociation and balanced charge transport. Consequently, the optimized systems exhibit simultaneous improvements in short-circuit current density and fill factor while preserving a high open-circuit voltage, delivering a power conversion efficiency of 19.2% (certified 19.04%) in small-area devices and 16.4% in large-area modules. In addition, the resulting devices demonstrate excellent operational stability. These findings provide insight into how charge-transfer efficiency can be enhanced through electrostatic-interaction-mediated energy-level regulation under low voltage loss and establish design guidance for high-performance A-D-A-type NFAs.