The use of single crystals has been fundamental to the development of semiconductor microelectronics and solid-state science. Whether based on inorganic or organic materials, the devices that show the highest performance rely on single-crystal interfaces, with their nearly perfect translational symmetry and exceptionally high chemical purity. Attention has recently been focused on developing simple ways of producing electronic devices by means of printing technologies. 'Printed electronics' is being explored for the manufacture of large-area and flexible electronic devices by the patterned application of functional inks containing soluble or dispersed semiconducting materials. However, because of the strong self-organizing tendency of the deposited materials, the production of semiconducting thin films of high crystallinity (indispensable for realizing high carrier mobility) may be incompatible with conventional printing processes. Here we develop a method that combines the technique of antisolvent crystallization with inkjet printing to produce organic semiconducting thin films of high crystallinity. Specifically, we show that mixing fine droplets of an antisolvent and a solution of an active semiconducting component within a confined area on an amorphous substrate can trigger the controlled formation of exceptionally uniform single-crystal or polycrystalline thin films that grow at the liquid-air interfaces. Using this approach, we have printed single crystals of the organic semiconductor 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C(8)-BTBT) (ref. 15), yielding thin-film transistors with average carrier mobilities as high as 16.4 cm(2) V(-1) s(-1). This printing technique constitutes a major step towards the use of high-performance single-crystal semiconductor devices for large-area and flexible electronics applications.

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Herein, we report the stabilization and modulation of layered-herringbone (LHB) packing, which is known to afford high-performance organic thin-film transistors, based on crystal structure analyses and calculations of intermolecular interaction energies for alkyl-substituted organic semiconductor (OSC) crystals. We systematically investigated the alkyl chain-length dependence of the crystal structures, solvent solubilities, and thermal characteristics for three series of symmetrically and asymmetrically alkyl-substituted benzothieno [3,2-b][1]benzothiophenes (BTBTs). All the series exhibit LHB packing when the BTBTs are substituted with relatively long alkyl chains (−C n H 2n+1 ), i.e., n ≥ 4 for monoalkylated, n ≥ 6 for dialkylated, and n ≥ 5 for phenyl-alkylated BTBTs. LHB packing is also evident in the nonsubstituted and diethyl-substituted BTBTs, although those substituted with short alkyl chains generally did not feature LHB packing because of their lack of interchain ordering. The density functional theory calculations of the intermolecular interactions revealed that the BTBT cores inherently generate LHB packing, and the stability is increasingly enhanced by the alignment of longer alkyl chains. It was also found that the LHB packing is stabilized by keeping the size ratios of the total intermolecular attractive forces between the T-shaped and slipped parallel contacts at about 3:2 for all the LHB compounds, despite the slight structural modifications generated by the substituents. We discuss the effects of alkyl substitutions to modulate the LHB packing of the BTBT cores and thus the two-dimensional carrier transport in layered OSC crystals.

Organic semiconductors may be processed in solution under ambient conditions; however, liquid manipulation on hydrophobic surfaces is difficult, which may hinder development of devices. Here, a push-coating technique is used to produce large-area semiconducting polymer films over hydrophobic surfaces.

We report structural, electronic, and field-effect transistor characteristics of layered crystalline donor–acceptor semiconductors with dialkylated benzothienobenzothiophenes.

Silver nanocolloid, a dense suspension of ligand-encapsulated silver nanoparticles, is an important material for printing-based device production technologies. However, printed conductive patterns of sufficiently high quality and resolution for industrial products have not yet been achieved, as the use of conventional printing techniques is severely limiting. Here we report a printing technique to manufacture ultrafine conductive patterns utilizing the exclusive chemisorption phenomenon of weakly encapsulated silver nanoparticles on a photoactivated surface. The process includes masked irradiation of vacuum ultraviolet light on an amorphous perfluorinated polymer layer to photoactivate the surface with pendant carboxylate groups, and subsequent coating of alkylamine-encapsulated silver nanocolloids, which causes amine–carboxylate conversion to trigger the spontaneous formation of a self-fused solid silver layer. The technique can produce silver patterns of submicron fineness adhered strongly to substrates, thus enabling manufacture of flexible transparent conductive sheets. This printing technique could replace conventional vacuum- and photolithography-based device processing.

Well-controlled carrier doping was performed in pentacene thin-film transistors (TFTs) by depositing additional organic acceptor (F4TCNQ) layers on top of existing channels. The doping concentration could be predefined by changing the area covered with the acceptor layer, which provides control of the threshold gate voltage, while keeping both the field-effect mobility (∼1.0cm2∕Vs) and the current on/off ratio (>105). The transport properties of these devices are discussed in terms of the trap and release model for the doped organic TFTs.

Polaron states in organic thin-film transistors (TFTs) were investigated by the electron spin resonance (ESR) technique. Gate-field-dependent and temperature-dependent single-Lorentzian ESR spectra were observed for field-induced polarons in pentacene TFTs, demonstrating the effect of motional narrowing due to polaron diffusion. Analyses of the ESR linewidth revealed a considerably long trapping time (tau_(C) approximately 0.7 ns), the variation of which is discussed in terms of the multiple trap-and-release model.