Characterization of Conducting Polymers for Organic Solar Cells

Thiophene based copolymers are widely studied as the donor active layer in bulk hetero junction polymer solar cells (PSCs). These copolymers, in some cases formed by an alternating structure of donor/acceptor units, can be fine tuned in their electronic energy levels in order to achieve better power conversion efficiencies values.1 The characterization of organic polymers for application in PSCs, or organic electronics in general, is multidisciplinary in nature, for it requires expertise within different branches of chemistry and at the border among chemistry, physics and engineering.2 As organic chemists, we have to check the structure and properties of these polymers and this is not always trivial. This contribution will be mainly focussed on the NMR characterization of polymers in solution and to the problems arising when aggregation occurs. This is particularly observed when benzodithiophene and thienothiophene (that are among the most popular units) are present in the backbone. NMR findings appear to be strongly correlated to solvatochromism or morphological properties