Tuning the stability of graphene layers by phthalocyanine-based oppv oligomers towards photo- and redoxactive materials

In contrast to pristine zinc phthalocyanine (1), zinc phthalocyanine based oPPV-oligomers (2–4) of different chain lengths interact tightly and reversibly with graphite, affording stable and finely dispersed suspensions of mono- to few-layer graphene—nanographene (NG)—that are photoactive. The p-type character of the oPPV backbones and the increasing length of the oPPV backbones facilitate the overall π–π interactions with the graphene layers. In NG/2, NG/3, and NG/4 hybrids, strong electronic coupling between the individual components gives rise to charge transfer from the photoexcited zinc phthalocyanines to NG to form hundreds of picoseconds lived charge transfer states. The resulting features, namely photo- and redoxactivity, serve as incentives to construct and to test novel solar cells. Solar cells made out of NG/4 feature stable and repeatable photocurrent generation during several ‘on-off’ cycles of illumination with monochromatic IPCE values of around 1%.