摘要
Achieving efficient and polarity-controllable charge transport remains a key challenge in the molecular design of nonfullerene acceptors (NFAs) for high-performance organic photovoltaics (OPVs) and organic field-effect transistors (OFETs). Here, we report two A-D-A-type NFAs, (CBPh)-Ph-i and (CBPh)-Ph-o featuring 4-hexylphenyl side chains strategically introduced at the concave and convex regions of a C-shaped ortho-benzodipyrrole (o-BDP) core, respectively. This side-chain engineering enables precise control of the molecular packing and charge-transport polarity. (CBPh)-Ph-i, with bay-region substitution, exhibits hole-dominant transport with a high OFET mu(h) of 0.59 cm(2) V-1 s(-1), due to its enhanced hole transfer integral associated with its triarylamine-based central core, along with its small energetic disorder for hole transport. In contrast, (CBPh)-Ph-o adopts a unique 3D grid-like packing motif that facilitates isotropic electron transport, delivering a high electron mobility of 0.24 cm(2) V-1 s(-1), driven by its larger electron transfer integral (V-e > V-h). This favorable charge-transport property translated into a high power conversion efficiency (PCE) of 15.98% in PM6:(CBPh)-Ph-o OPVs, which was further enhanced to 17.24% upon incorporation of Y6-16 as a third component. These results demonstrate that rational side-chain engineering of o-BDP-based NFAs provides a powerful strategy to tune molecular packing and control the charge-transport polarity.