Enhancing Photovoltaic Performance of Nonfused-Ring Electron Acceptors via Asymmetric End-Group Engineering and Noncovalently Conformational Locks

By employing the asymmetric end-group engineering, an asymmetric nonfused-ring electron acceptor (NFREA) was designed and synthesized. Compared with the symmetric analogs (NoCA-17 and NoCA-18), NoCA-19 possesses broader light absorption range, more coplanar pi-conjugated backbone, and appropriate crystallinity according to the experimental and theoretical results. The organic solar cells based on J52:NoCA-19 exhibited a power conversion efficiency as high as 12.26%, which is much higher than those of J52:NoCA-17 (9.50%) and J52:NoCA-18 (11.77%), mainly due to more efficient exciton dissociation, better and balanced charge mobility, suppressed recombination loss, shorter charge extraction time, longer charge carrier lifetimes, and more favorable blend film morphology. These findings demonstrate the great potential of asymmetric end-group engineering in exploring low-cost and high-performance NFREAs.