Influence of the processing solvent on the photoactive layer nanomorphology of P3HT/PC60BM solar cells

In this article, it is demonstrated that doctor blading of thin poly-3-hexylthiophene/phenyl-C61-butyric acid methyl ester (1/1) bulk-hetero junction films from toluene leads to an improved nanocrystallinity, when compared with their unannealed chlorobenzene processed counterparts. This difference in morphology was demonstrated by solid-state NMR and Rapid Heating Cooling Calorimetry (RHC), being useful complementary techniques to investigate the active layer morphology of photovoltaic devices. An increased PC60BM nanocrystallinity is indicated by several NMR relaxation decay times (T1C, T1H, and T1?H) and confirmed by an increase of the melting enthalpy in RHC experiments. An improved solar cell performance further strengthens this conclusion.