Efficient strategies to improve photovoltaic performance of linear-shape molecules by introducing large planar aryls in molecular center and terminals

Three novel linear-shape small molecules (SMs) of TPA(DPP-PN)2, Cz(DPP-PN)2 and Fl(DPP-PN)2 were prepared with the same side-arms of diketopyrrolopyrrole (DPP)-phenanthrene (PN) and different central units of triphenylamine (TPA), carba-zole (Cz) and fluorene (Fl). The SMs with planar central units exhibited better photo-voltaic properties than TPA(DPP-PN)2 with a non-planar TPA in solution-processed OSCs. The highest power conversion efficiency of 4.13% was obtained in the Fl- (DPP-PN)2 based solar cells, which is 1.87 times value of the TPA(DPP-PN)2 based cells.