The advent of nonfullerene acceptors (NFAs) enabled records
of
organic photovoltaics (OPVs) exceeding 19% power conversion efficiency
in the laboratory. However, high-efficiency NFAs have so far only
been realized in solution-processed blends. Due to its proven track
record in upscaled industrial production, vacuum thermal evaporation
(VTE) is of prime interest for real-world OPV commercialization. Here,
we combine the benchmark solution-processed NFA Y6 with three different
evaporated donors in a bilayer (planar heterojunction) architecture.
We find that voltage losses decrease by hundreds of millivolts when
VTE donors are paired with the NFA instead of the fullerene C60, the current standard acceptor in VTE OPVs. By showing that
evaporated small-molecule donors behave much like solution-processed
donor polymers in terms of voltage loss when combined with NFAs, we
highlight the immense potential for evaporable NFAs and the urgent
need to direct synthesis efforts toward making smaller, evaporable
compounds.