2-Hexylthieno[3,2-b]thiophene-substituted anthracene derivatives for organic field effect transistors and photovoltaic cells

Novel 2-hexylthieno[3,2-b]thiophene-containing conjugated molecules have been synthesized via a reduction reaction using tin chloride in an acidic medium. They exhibited good solubility in common organic solvents and good self-film and crystal-forming properties. The single-crystalline objects were fabricated by a solvent slow diffusion process and then were employed for fabricating field-effect transistors (FETs) along with thinfilm transistors (TFTs). TFTs made of 5 and 6 exhibited carrier mobility as high as 0.10-0.15 cm ²V ^-1s ^-1. The single-crystal-based FET made of 6 showed 0.70 cm ²V ^-1s ^-1 which was relatively higher than that of the 5-based FET (μ = 0.23 cm ²V ^-1s ^-1). In addition, we fabricated organic photovoltaic (OPV) cells with new 2-hexylthieno [3,2-b]thiophene-containing conjugated molecules and methanofullerene [6,6]-phenyl C61-butyric acid methyl ester (PC ₆₁BM) without thermal annealing. The ternary system for a bulk heterojunction (BHJ) OPV cell was elaborated using PC ₆₁BM and two p-type conjugated molecules such as 5 and 7 for modulating the molecular energy levels. As a result, the OPV cell containing 5, 7, and PC ₆₁BM had improved results with an open-circuit voltage of 0.90 V, a short-circuit current density of 2.83 mA/cm ², and a fill factor of 0.31, offering an overall power conversion efficiency (PCE) of 0.78%, which was larger than those of the devices made of only molecule 5 (η ∼ 0.67%) or 7 (η ∼ 0.46%) with PC ₆₁BM under identical weight compositions.