Strategic engineering of H-/J-aggregation equilibrium in non-fullerene acceptors toward high-performance organic photovoltaics

Strategic molecular engineering of asymmetric small-molecule acceptors (SM-EH, SM-BO, SM-HD) featuring alkoxyphenyl/2-octyldodecyl inner side chains enables precise H-aggregation control, enhancing vertical electron transport in organic solar cells (OSCs). Incorporating these SMAs into PM6:Y6 ternary systems elevates power conversion efficiency (PCE) to 18.06% (PM6:Y6:SM-BO), while extending this design to PM6:L8-BO achieves a record 20.0% PCE. Mechanistic investigations demonstrate that balanced H-aggregation: reduces energy loss, accelerates exciton dissociation, and balances charge mobility. Crucially, we identify excessive H-aggregation impairs charge transfer, establishing H-/J-aggregation equilibrium as essential for optimal performance. This work establishes aggregation engineering—specifically targeting the H-aggregation of SMA—as a universal strategy for high-efficiency OSCs, with notable achievements in this field, and achieves a 20% PCE through ternary morphology optimization.