Acceptor-donor-acceptor type compounds W1–W3 were designed and synthesized. These compounds had the same donor moiety of 2,6-di(thiophen-2-yl)dithieno[3,2-b:2′,3′-d]thiophene and different acceptor groups of 2-dicyanomethylen-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran (TCF), dicyanovinyl (DCV) and 3-ethyl-2-thioxothiazolidin-4-one. Experimental results showed all compounds had high thermal stability and strong absorption in the visible light region. Among them, compound W1 with TCF as acceptor group displayed the lowest LUMO energy level of −3.74 eV and the smallest HOMO-LUMO band gap of 1.74 eV, suggesting the potential applications of TCF unit in low band gap organic semiconductors.

A series of dicyanomethylene-substituted 2,5-di(thiophen-2-yl)thieno[3,2-b]thieno-quinoids, in which soluble alkyl chains (2-decyltetradecyls) are substituted at different positions (namely, 2,2′-positions (Compound 1); 3,3′- positions (Compound 2); 6,6′-positions (Compound 3)), are strategically designed and successfully synthesized. The photophysical and electrochemical properties as well as molecular packing of these new compounds are thoroughly investigated. Thin film transistor measurements reveal that Compounds 1–3 display markedly different charge transport performance. The solution processed thin film transistors of Compound 2 exhibits the highest electron mobility of up to 0.22 cm² V⁻¹ s⁻¹ under ambient conditions, one and three orders of magnitude higher than those of Compounds 3 and 1, respectively, demonstrating the strong impact of alkyl chain orientations on transistor performance.

New ladder-type π-conjugated polymer poly{6-alkyl-pyrrolo[3,2-b:4,5-b′]bis-[1,4]benzothiazine} (PPBBTZ) was synthesized through a simple method. PPBBTZ showed good solubility in organic solvents (such as chloroform, tetrahydrofuran, chlorobenzene, o-dichlorobenzene) and high thermal stability (decomposition temperatures up to 323 °C and 299 °C in nitrogen and air, respectively). The highest occupied molecular orbital and lowest unoccupied molecular orbital energy level estimated from electrochemistry result and absorption spectrum were −5.46 and −3.81 eV, respectively, with a band gap of 1.65 eV. More interestingly, PPBBTZ displayed broad absorption from ultraviolet to visible light regions (200–750 nm). These properties suggested PPBBTZ was a good candidate in opto-electronics. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Charge transport in organic semiconductors is strongly dependent on their molecular packing modes in the solid state. Therefore, understanding the relationship between molecular packing and charge transport is imperative, both experimentally and theoretically. However, so far, the fundamental effects of solid-state packing and molecular interactions (e.g. NH⋅⋅⋅π) on charge transport need further elucidation. Herein, indolo[3,2-b]carbazole (ICZ) and a derivative thereof are used as examples to approach this scientific target. An interesting insight obtained thereby is that NH⋅⋅⋅π interactions among ICZ molecules facilitate charge transport for higher mobility. Subtle changes in the of NH⋅⋅⋅π interactions can significantly influence both the molecular packing and the charge-transport properties. Therefore, a method for exploiting intermolecular NH⋅⋅⋅π interactions would yield novel molecular systems with designable characteristics.