Effect of 4-biphenyl groups on the charge transport and photovoltaic properties of arylamine based push-pull systems

Two push-pull derivatives based on a N,N-bis(4-biphenylyl)aniline (BPA) donor block connected to a dicyanovinyl accepting moiety by thienyl and bithienyl π-conjugated spacers have been synthesized and characterized. All-small-molecule planar-heterojunction organic solar cells show promising power conversion efficiencies and impressive fill factor (>73%) correlated with the high hole-mobility induced by the BPA moiety.