Organic
photovoltaics (OPVs) have made enormous progress in recent
years, benefiting from the rapid development of non-fullerene acceptors
(NFAs). Most high-performance NFAs, however, have featured π-conjugated
backbones with large-fused core structures, increasing the complexity
and cost of their synthesis and limiting their practical commercialization.
In this study, we synthesized a series of acceptor–donor–acceptor-configured
small-molecule acceptors (NTCPDTCN, NTCPDTID, and NTCPDT2F) based
on a core structure featuring a naphthobisthiadiazole (NT) group and
two cyclopenta[2,1-b,3,4-b′]dithiophene
(CPDT) groups as the unfused-ring central unit and equipping malononitrile
(CN), 2-(3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile
(ID), and 2-(5,6-difluoro-3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile
(2F) groups as terminal groups. When blended with PM7, the NTCPDTCN-containing
binary device displayed a high open-circuit voltage (V
OC) of 1.04 V, without self-aggregation, as well as the
best device performance. When blended with PM6:Y6, the ternary NTCPDTCN-,
NTCPDTID-, and NTCPDT2F-based OPVs provided power conversion efficiencies
of 15.4 ± 0.09, 14.6 ± 0.15, and 16.0 ± 0.08%, respectively.
NTCPDT2F provided complementary absorption and allowed fine-tuning
of the blend morphology, resulting in suppression of charge recombination
and improvements in charge generation and collection, thereby achieving
the highest device performance. Thus, our findings might provide some
directions for developing high-performance ternary OPVs through the
introduction of unfused-ring small-molecule acceptors.
