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

Abstract

Abstract 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, B-BDP 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 (105 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 Jsc of 11.84 mA cm2 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.