Two-dimensional π-conjugated molecules based-on 2,6,9,10-tetra(prop-1- yn-1-yl)anthracene and their application to solution-processed photovoltaic cells

Novel two-dimensional π-conjugated molecules, i.e., 5′, 5″′-((9,10-bis((4-hexylphenyl)ethynyl)anthracene-2,6-diyl) bis(ethyne-2,1-diyl))bis(5-hexyl-2,2′-bithiophene) (2,6-HBT) and 5′,5″′-((2,6-bis((4-hexylphenyl)ethynyl)anthracene-9,10-diyl) bis(ethyne-2,1-diyl))bis(5-hexyl-2,2′-bithiophene) (9,10-THB) were successfully synthesized and utilized as highly soluble p-type organic semiconductors for organic thin film transistors (TFTs) and solar cells. From the TFTs, the high hole mobility of the pristine film of 9,10-THB was measured to be 0.07 cm² V^-1 s^-1 (I_on/off = 10⁶-10⁷), which is mainly attributed to slip-stacked charge-transport behavior in J-aggregation-induced crystallites. Further, a solution-processed solar cell made of 9,10-THB and PC₆₁BM exhibited very promising and reproducible power conversion efficiencies of 3.30% and 2.53% with composition 1:1 and 1:2 w/w ratio, respectively.