Organic photovoltaics (OPVs) have progressed steadily
through three
stages of photoactive materials development: (i) use of poly(3-hexylthiophene)
and fullerene-based acceptors (FAs) for optimizing bulk heterojunctions;
(ii) development of new donors to better match with FAs; (iii) development
of non-fullerene acceptors (NFAs). The development and application
of NFAs with an A–D–A configuration (where A = acceptor
and D = donor) has enabled devices to have efficient charge generation
and small energy losses (E
loss < 0.6
eV), resulting in substantially higher power conversion efficiencies
(PCEs) than FA-based devices. The discovery of Y6-type acceptors (Y6
= 2,2′-((2Z,2′Z)-((12,13-bis(2-ethylhexyl)-3,9-diundecyl-12,13-dihydro-[1,2,5]-thiadiazolo[3,4-e]-thieno[2″,3″:4′,5′]thieno-[2′,3′:4,5]pyrrolo-[3,2-g]thieno-[2′,3′:4,5]thieno-[3,2-b]indole-2,10-diyl)bis(methanylylidene))bis(5,6-difluoro-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))dimalononitrile) with an A–DA′ D–A
configuration has further propelled the PCEs to go beyond 15% due
to smaller E
loss values (∼0.5 eV)
and higher external quantum efficiencies. Subsequently, the PCEs of
Y6-series single-junction devices have increased to >19% and may
soon
approach 20%. This review provides an update of recent progress of
OPV in the following aspects: developments of novel NFAs and donors,
understanding of the structure–property relationships and underlying
mechanisms of state-of-the-art OPVs, and tasks underpinning the commercialization
of OPVs, such as device stability, module development, potential applications,
and high-throughput manufacturing. Finally, an outlook and prospects
section summarizes the remaining challenges for the further development
of OPV technology.
