ИСТИНА

The 3rd generation of polymers for organic photovoltaics is designed on basis of alternated donor and acceptor units. Such structures result in a narrowed bandgap and increased absorption in the red which is advantageous for solar light harvesting. Here we use VIS-pump IR-probe ultrafast spectroscopy to compare photovoltaic blends based on a novel polymer P1 comprising TBTBT units and PCDTBT as a reference from the viewpoint of charge separation dynamics. We demonstrate that P1/PC70BM blends provide efficient charge separation, and the hole-transfer process plays significant role in free charge generation. However, unlike PCDTBT/PC70BM blends with close-to-optimal phase separation, in P1/PC70BM blends with high fullerene loadings part of the charges seems to be lost in large PC70BM domains. Thus, the efficiency of P1-based organic solar cells likely may be optimized via tuning the blend nanostructure.