Novel A-D-A type small molecules with β-alkynylated BODIPY flanks for bulk heterojunction solar cells

A serial of novel A-D-A type small molecules with BODIPY linked through alkynyl with various electron donor units such as fluorene, carbazole, benzodithiophene and phenothiazine, namely F-BDP, C-BDP, BBDP and P-BDP, respectively, were designed and synthesized. Introducing the alkynyl bridge leads to extending the molecular absorption spectrum to the range of 320-700 nm with high molar extinction coefficients (10(5) cm(-1) M-1) and strong fluorescence quenching. The molecules showed relatively low HOMO ranging from -5.02 to -5.24 eV as estimated from cyclic voltammetry measurements. Interestingly, B-BDP with BDT as donor exhibits more obviously red-shifted absorption in the solid state compared to F-BDP, C-BDP and P-BDP. Furthermore, the solution-processed bulk-heterojunction organic solar cell based on B-BDP/PC71BM present superior charge transport property and more favorable nanoscale morphology, resulting in a significant higher J(sc) of 11.84 mA cm(2) and FF than the other counterparts, thus achieved a higher PCE of 4.65%, which is one of the best values among the ever reported BODIPY based organic solar cells. (C) 2017 Elsevier B.V. All rights reserved.