Controlling exciton diffusion and fullerene distribution in photovoltaic blends by side chain modification

The authors thank the European Research Council for financial support (grant number 321305). I.D.W.S. acknowledges a Royal Society Wolfson Research Merit Award. A.J.W. is thankful to the Scottish Doctoral Training Centre for financial support (grant number EP/L015110/1) and A.R. is thankful to EPSRC for financial support (grant number EP/J009016). C.K. acknowledges financial support from the “Thü ringer Landesgraduiertenschule für Photovoltaik” (PhotoGrad). C.K. and H.H. are grateful to the “Deutsche Forschungsgemeinschaft” (DFG) for financial support within the priority program SPP1355.The influence of crystallinity on exciton diffusion and fullerene distribution was investigated by blending amorphous and semicrystalline copolymers. We measured exciton diffusion and fluorescence quenching in such blends by dispersing fullerene molecules into them. We find that the diffusion length is more than two times higher in the semicrystalline copolymer than in the amorphous copolymer. We also find that fullerene preferentially mixes into disordered regions of the polymer film. This shows that relatively small differences in molecular structure are important for exciton diffusion and fullerene distribution.Publisher PDFPeer reviewe