IR sensitization of an indene-C60 bisadduct (ICBA) in ternary organic solar cells

This article presents a smart strategy to successfully tackle two main limitations of organic solar cells (OSCs) in one step: the narrow absorption window of polymers as well as the Voc limitation related to the mono-PCBM. We demonstrate the high OSC performance of >5% in the combination of a fullerene multiadduct, i.e. indene-C60 bisadduct (ICBA) with a low bandgap polymer employing the concept of ternary OSCs. Solar cells achieving a fill factor (FF) of >60% along with high quantum efficiency in the near IR region are demonstrated for ternary composites consisting of P3HT, the fullerene-bisindene adduct of ICBA and a low bandgap copolymer sensitizer. Using P3HT as an efficient transport matrix with non-Langevin recombination dynamics allowed us to limit and overcome the otherwise dominant recombination losses of the indene-C60 bisadduct – low bandgap copolymer blends. The success of this strategy resulted in a relative efficiency improvement of over 25%.