Side-Chain-Modulated Charge Transport Polarity in Curved Ortho -Benzodipyrrole-Based Acceptors for High-Performance Organic Photovoltaics and Transistors

High Resolution Image Download MS PowerPoint Slide 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, CB i Ph and CB o Ph 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. CB i Ph, with bay-region substitution, exhibits hole-dominant transport with a high OFET μ 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, CB o Ph 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:CB o Ph 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.