Facile access to high-performance organic solar cells through an A-D1-D2-A type unfused non-fullerene acceptors

Abstract

In recent years, the small molecule acceptors (SMAs) possessing near-infrared (NIR) absorption have aroused interest in organic solar cells (OSCs). Herein, two novel NIR region SMAs with an A-D1-D2-A type asymmetric unfused-ring cores, namely, DPCT-4F and DPCT-4Cl, are originally designed and synthesized through the conjugation of a centrosymmetrical dipyran (DTDP) donor (D1) unit, a cyclopentadithiophene (CPDT) donor (D2) unit and halogenated 1,1-dicyanomethylene-3-indanone (DCI) acceptor (A) terminals. Both the SMAs presented strong NIR absorption at about 1000 nm. The influences of different halogenated terminals on physicochemical properties and on optoelectronic properties are systematically investigated. Compared with the DPCT-4F bearing fluorinated end atoms, the chlorinated DPCT-4Cl exhibits a higher molar absorptivity, lower narrow bandgap and higher dipole moment. After blended with polymer donor PBDB-T, the OSCs based on PBDB-T:DPCT-4Cl shows an impressive power conversion efficiency (PCE) of 12.13%, which is much higher than that of 11.08% for the DPCT-4F-based ones. The obtained PCE of 12.13% is one of the highest values reported for asymmetric unfused-ring SMAs based binary OSCs so far. Overall, this work clearly proves that the SMAs with an A-D1-D2-A type asymmetric unfused-ring framework is a promising design strategy for high performance OSCs.