Azaacene Dimers – Novel Acceptor Materials with a ‘Twist’

The synthesis of five spiro-linked azaacene dimers is reported and their properties are compared to that of their monomers. Dimerization quenches emission of the longer (>/=(hetero)tetracenes) derivatives and furnishes amorphous thin-films, the absorption is not affected. The larger derivatives were tested as acceptors in bulk-heterojunction photovoltaic devices with a maximum power conversion efficiency of up to 1.6 %.