Non-fused ring electron acceptor based on phenyl-substituted benzodithiophenedione unit via chlorinated terminal groups for constructing efficient organic solar cells

Non-fused ring electron acceptors (NFREAs) have displayed promising candidates for practical application of organic solar cells (OSCs) owing to their short synthesis routes and cost effectiveness. The terminal groups halogenation have facilitated the optimization the physicochemical properties of NFREAs. In this work, we developed two NFREAs using a phenyl-substituted benzodithiophenedione unit as central core and electron-withdrawing groups 2-(3-oxo-2,3-dihydro-1 H-inden-1-ylidene) malononitrile (IC) or chlorinated IC (IC-2Cl) as the terminal groups. These NFREAs were designated as BDDPh-H and BDDPh-Cl, respectively. DFT calculations revealing that both NFREAs exhibited good backbone coplanarity due to S…O noncovalent interactions, and BDDPh-Cl exhibited red-shifted absorption compared with BDDPh-H owing to the stronger molecular stacking caused by chlorinated terminal groups. Moreover, BDDPh-Cl-based blended film demonstrated better nano-scale morphology, facilitating exciton dissociation and charge transport. Thus, PM6: BDDPh-Cl-based OSCs achieved a higher power conversion efficiency (PCE) of 12.69 %, outperforming BDDPh-H-based device (3.20 %) due to the enhanced short-circuit current and fill factor. Our findings indicate that combining phenyl-substituted benzodithiophenedione as central unit with chlorinated terminal groups showed great potential to construct highly efficient NFREAs.