5′-(Anthracene-9,10-diyl)bis(ethyne-2,1-diyl)bis(2-hexylthiophene) derivatives bearing 5-ethynyl-5′-hexyl-2,2′-bithiophene and 2-ethynyl-5-hexylthieno[3,2-b]thiophene: Thin film transistors and photovoltaic applications

Novel 5,5′-(anthracene-9,10-diyl)bis(ethyne-2,1-diyl)bis(2-hexylthiophene)-based conjugated molecules have been synthesized via the Sonogashira coupling reaction. Newly synthesized anthracene-based molecules exhibit good solubility in common organic solvents and good self-film-forming properties. The semiconducting properties of the two molecules were evaluated in organic thin film transistors (OTFTs). The two π-conjugated molecules 4 and 7 exhibit fairly high charge carrier mobilities—as high as 0.010–0.022 cm2 V−1 s−1 (Ion/Ioff > 103)—without any annealing process. The high charge carrier mobilities of the as-spun films are attributed to the fact that the molecules demonstrated pronounced J-aggregation behavior, resulting in easy crystallization and dense coverage of the surface of a dielectric layer. In addition, two molecules were employed to fabricate organic photovoltaic (OPV) cells with methanofullerene [6,6]-phenyl C61-butyric acid methyl ester (PC61BM) without thermal annealing. As a result, the photovoltaic cell containing 7 had the best preliminary results with an open-circuit voltage of 0.92 V, a short-circuit current density of 1.82 mA/cm2, and a fill factor of 0.32, offering an overall power conversion efficiency (PCE) of 0.54%.

Research highlights
► Soluble p-type semiconducting materials based on anthracene unit.
► Those molecules showed very good film forming properties.
► Two-dimensional conjugated structures.
► High field effect mobility in TFT devices.
► The molecules were applied to solar cells (power conversion efficiency = 0.5–0.6%).