We designed and synthesized a new ladder-type planar building block function as donor moieties, extending the BDT unit at 4,8-positions and using carbon-bridge incorporating into the backbone to form a five-ring fused structure named f-DTBDT, preventing the dihedral angle between the thienyl ring and benzene core. The new designed f-DTBDT building block shows a promising application in the field of the organic semiconductor materials. When the f-DTBDT ended up with 2HIC, 2FIC and 2ClIC to get three acceptor-donor- acceptor (A-D-A) structural compounds, DTBDT-IC, DTBDT-4F and DTBDT-4Cl, respectively. The three non-fullerene small molecule acceptors (NFSMAs) show outstanding thermal stability, the decomposition temperatures (5% weight loss) of three NFSMAs were over 340 degree. Due to the strong electron deficient properties of the terminal groups, there is strong intramolecular charge transfer between the intramolecular A-D units, resulting in a strong absorption in Vis-NIR region. HOMO and LUMO energy levels of the new non-fullerene small molecule acceptors are perfectly match with the successful wide bandgap polymer PBDB-T-2F. We fabricated the bulk heterojunction (BHJ) organic solar cells (OSCs) devices based the active layer of new NFSMAs blended with polymer donor PBDB-T-2F, an optimized PCE of 10.15 % was obtained for PBDB-T-2F:DTBDT-4F based device. These results indicate the new f-DTBDT is an prospective building block for organic semiconductor materials.

Ladder-type non-fullerene small molecule acceptors based on short-axis direction fused benzodithiophene building block for efficient organic solar cells

ACS Fall 2021

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