Synergistic Molecular Engineering of Fully Non-fused Ring Acceptors for Achieving Efficient Zigzag Charge Transport Channel and Low Non-Radiative Voltage Loss.

Fully non-fused ring acceptor (FNFRA) are potentially important for boosting the performance and lowering the material costs of organic solar cells (OSCs). Despite their potential, FNFRA-based OSCs have not yet matched the performance of their fused ring and partial non-fused ring counterparts due to limited molecular engineering research. In this work, by incorporating a synergistic strategy of tailoring the β-side chain and end-group of FNFRA with the cyclic "belt" simultaneously, a FNFRA named C6FT-2F2Cl is constructed. Compared with other symmetric FNFRAs, C6FT-2F2Cl features a shorter π-π stacking distance and an efficient zigzag charge transport channel, leading to enhanced and balanced charge carrier mobilities, lower non-radiative energy loss and a higher short-circuit current density. The power conversion efficiency (PCE) of the C6FT-2F2Cl-based OSC reached 13.19%, which is among the best in FNFRA-based devices. This work provides new valuable insights for the charge transport mechanism associated FNFRAs and paves a new route to the materials design toward high-performance and low-cost OSCs.