Bandgap acceptor units

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Thiophene-based copolymers incorporating the dioxide unit 29 have lower bandgaps than non-oxidized analogues (due to the increased electron affinity directed by the acceptor unit) and this feature could be... 

While donor units are primarily used to maintain appropriate HOMO levels in D-A copolymers, acceptor units are largely responsible for the control of the LUMO level. This is particularly important for D-A copolymers used for organic solar cells, since the more desirable narrow bandgap can be achieved by carefully selecting strong acceptor units. Due to the electron-deficient nature of these acceptor moieties, their syntheses often involve harsh conditions and quite delicate chemistry. Below we will briefly describe the synthesis of several important acceptor units that have contributed to the discovery of D-A copolymers of exceptional performance in organic electronics. 

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