Fluorine substitution for aggregation transformation and exciton dissociation acceleration in non-fused electron acceptors

• We developed a class of non-fused non-fullerene acceptors to match with polymer donor poly(3-hexylthiophene). • The fluorinated bridge unit enables H- and J-aggregation transformation. • Efficient exciton dissociation and charge transport render an enhanced higher power conversion efficiency. In order to enable low-cost manufacture of organic solar cells (OSCs), it is very important to develop non-fused electron acceptors to match with one of the cheapest polymer donors, poly(3-hexylthiophene) (P3HT). However, the lower exciton dissociation and charge transfer are still the main factors that limit the improvement of P3HT-based OSCs. Herein, we designed one class of A 2 -A 1 -D-A 1 -A 2 type non-fused electron acceptors and synthesized BTA34 and F-BTA34 by introducing benzo[ d ][1,2,3] triazole as the bridged unit. The dominated H-aggregation in F-BTA34 affords high degree of crystalline and proper phase separation when blended with polymer P3HT, which ensure efficient exciton dissociation and higher charge carrier mobility. Consequently, P3HT:F-BTA34 devices demonstrate a better performance with higher short-circuit current and fill factor. The blend of P3HT:BTA34 exhibits a broader distribution of the mixing domains, resulting in relative longer-lived charge species. This work provides useful strategies to design non-fused electron acceptors to match with P3HT from the perspective of simultaneously improving exciton dissociation and suppressing charge recombination.