Efficient fully non-fused electron acceptor solar cells enabled by acceptor crystallization induced fibril network morphology

Fully non-fused electron acceptors (FNEAs) exhibit great potential as cost-effective electron acceptors for organic solar cells (OSCs). However, the device performance of FNEAs in OSCs is hindered by weak acceptor crystallinity associated with the rotation of carbon-carbon single bonds. Herein, we report the formation of strong molecular crystallinity of FNEAs and thus favorable fibril network morphology in blend films by finely optimizing the thermal annealing temperature. This favorable morphology not only enhanced the diffusion distance and dissociation efficiency of excitons in the acceptor phase, but also significantly boosted the electron mobility and carrier extraction rate. Consequently, a power conversion efficiency of 17.3% along with a short-circuit current density of 27.7 mA cm−2 are obtained, which are both the highest values for OSCs employing fully non-fused electron acceptors. These results demonstrate promising prospects and provide valuable insights for achieving high-efficiency OSCs using low-cost FNEAs.