Triisopropylsilylethynyl-substituted indenofluorenes: carbonyl versus dicyanovinylene functionalization in one-dimensional molecular crystals and solution-processed n-channel OFETs

• Published in: ORGANIC CHEMISTRY FRONTIERS Vol. 5; no. 20; pp. 2912 - 2924
• Main Authors: Ozdemir, Resul, Park, Sangyun, Deneme, Ibrahim, Park, Yonghan, Zorlu, Yunus, Alidagi, Husniye Ardic, Harmandar, Kevser, Kim, Choongik, Usta, Hakan
• Format: Journal Article
• Language: English
• Published: CAMBRIDGE Royal Soc Chemistry 21.10.2018; Royal Society of Chemistry
• Subjects: Axes (reference lines); Carbonyl compounds; Carbonyls; Carrier mobility; Channel morphology; Chemical synthesis; Chemistry; Chemistry, Organic; Crystal structure; Crystallography; Crystals; Current carriers; Molecular orbitals; N-type semiconductors; Optoelectronics; Organic chemistry; Organic semiconductors; Physical Sciences; Polycyclic aromatic hydrocarbons; Science & Technology; Semiconductors; Shearing; Single crystals; Substitutes; Thin films; Tips; DESIGN; ACENES; ELECTRON-MOBILITY; ORGANIC SEMICONDUCTOR; PERFORMANCE; CHARGE-TRANSPORT; THIN-FILM TRANSISTORS; PENTACENE; FIELD-EFFECT TRANSISTORS; ACCEPTOR
• ISSN: 2052-4129; 2052-4110; 2052-4110
• DOI: 10.1039/c8qo00856f

The design and synthesis of novel electron-deficient and solution-processable polycyclic aromatic hydrocarbons offers great opportunities for the development of low-cost and large-area (opto)electronics. Although (trialkylsilyl)ethynyl (R3Si-C?C-) has emerged as a very popular unit to solubilize organic semiconductors, it has been applied only to a limited class of materials that are mostly substituted on short molecular axes. Herein, two novel solution-processable indenofluorene-based semiconductors, TIPS-IFDK and TIPS-IFDM, bearing (triisopropylsilyl)ethynyl end units at 2,8-positions (long molecular axis substitution) were synthesized, and their single-crystal structures, optoelectronic properties, solution-sheared thin-film morphologies/microstructures, and n-channel field-effect responses were studied. In accordance with the DFT calculations, the HOMO/LUMO energies of the new compounds are found to be -5.77/-3.65 eV and -5.84/-4.18 eV for TIPS-IFDK and TIPS-IFDM, respectively, reflecting the high electron deficiency of the new -backbones. Both semiconductors exhibit slightly S-shaped molecular frameworks with highly coplanar IFDK/IFDM -cores, and they form slipped -stacked one-dimensional (1-D) columnar motifs in the solid state. However, substantial differences in the degree of - interactions and stacking distances (4.04 angstrom vs. 3.47 angstrom) were observed between TIPS-IFDK and TIPS-IFDM as a result of carbonyl vs. dicyanovinylene functionalization, which results in a three orders of magnitude variation in the charge carrier mobility of the corresponding thin films. Top-contact/bottom-gate OFETs fabricated via solution-shearing TIPS-IFDM yielded one of the best performances in the (trialkylsilyl)ethynyl literature ((e) = 0.02 cm(2) V-1 s(-1), I-on/I-off = 10(7)-10(8), and V-T approximate to 2 V under ambient atmosphere) for a 1-D polycrystalline semiconductor microstructure. To the best of our knowledge, the molecules presented here are the first examples of n-type semiconductors substituted with (trialkylsilyl)ethynyl groups on their long molecular axes.