Low-bandgap non-fullerene acceptors based on selenophene π spacer and alkylated indaceno[1,2-b:5,6-b′]dithiophene for organic solar cells

Abstract

Three non-fullerene acceptors, i.e. IDT2SeC2C4, IDT2SeC2C42F and IDT2SeC2C44F, with selenophene π bridge between central alkylated indaceno[1,2-b:5,6-b′]dithiophene (IDT) unit and terminal 1,1-dicyanomethylene-3-indanones (ICs) with 0–2 fluorine substituents were synthesized. These molecules presented low optical band gaps in the range of 1.30–1.44 eV. Moreover, compared with the counterparts with phenyl side chains on IDT unit, the alkyl-based molecules achieved higher electron mobility owing to the more ordered and closer π-π stacking. Organic solar cells (OSCs) based on the non-fullerene acceptors were fabricated with the wide band gap polymer PBDB-T as donor. Attributed to the desired morphology with more obvious fibril-like structures, the devices based on IDT2SeC2C42F and IDT2SeC2C44F with fluorinated IC terminals delivered high power conversion efficiencies (PCEs) over 10%, whereas the devices based on DT2SeC2C4 showed a lower PCE of 8.92%.