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We show here that thermal imaging, a nonlithographic technique which enables printing multiple, successive layers via a dry additive process can be used in combination with tailored printable conductors in the fabrication of organic electronic devices. This method is capable of patterning a range of organic materials at high speed over large areas with micron size resolution and excellent electrical performance avoiding the solvent compatibility issues currently faced by alternative techniques. Such a dry, potentially reel-to-reel printing method may provide a practical route to realizing the expected benefits of plastics for electronics. We illustrate the viability of thermal imaging and imageable organics conductors by printing a functioning, large area ͑4000 cm 2 ͒ active matrix backplane display circuit containing several thousand transistors.

We prepared by vapor deposition at room temperature thin (500 Å) Co/Pt multilayers or layered structures directly onto glass or Si substrates. They show a preferential magnetization perpendicular to the film plane for Co thicknesses below 12 Å and a 100% perpendicular remanence for Co thicknesses below 4.5 Å. The magnetic anisotropy can be explained by an interface contribution to the anisotropy. We also investigated the magneto-optical (MO) polar Kerr effect of these multilayers. Because of their excellent magnetic properties and their potentially high oxidation and corrosion resistance, these Co/Pt-layered structures are very promising candidates for MO recording. The Kerr rotation θk at λ=820 nm for a 35×(4.0 Å Co+12.7 Å Pt)-layered structure, which has 100% magnetic remanence, is modest (−0.12°), but the reflectivity R is high (70%), which results in a respectable figure of merit Rθ2k. Furthermore, the Kerr effect increases towards shorter wavelengths and thus favors future higher-density recording.

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This letter reports on the unexpected dependence of contact resistance on the dielectric layer for pentacene thin film transistors with printed organic conducting electrodes. While the intrinsic mobility is weakly reliant on the dielectric, the contact resistance does vary considerably with dielectric layer. We show that while morphological changes are not apparent, contact resistances vary by an order of magnitude. This result suggests that the barrier to charge injection may depend not only on interactions at the complex triple interface but also on the details of the electronic structure at the semiconductor/dielectric interface.

Polyaniline/single wall carbon nanotube composites were prepared to be used as printable conductors for organic electronics devices. We show here that the high aspect ratio of single wall carbon nanotubes enables percolation into a conducting network at extremely low nanotube concentration. The nature of the transport mechanism is revealed by the temperature dependence of the conductivity of these percolating composites. We demonstrate here that these thin composite films are printable via laser ablation with high resolution while retaining appropriate conductivity. The utility of these findings is illustrated by printing structures, which could serve as a source and drain with 7 μm channel and 2 S/cm conductivity for use in plastic transistors.

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The electrical performance of organic thin-film transistors (TFTs) often degrades when the devices are exposed to air. This is generally ascribed to the generation of trap states, [1] possibly as a result of the oxidation of the organic semiconductor.[2] One strategy to improve the stability of p-channel organic TFTs is the synthesis of conjugated semiconductors with a relatively large ionization potential. [3][4][5][6][7][8] However, most of the TFTs based on organic semiconductors with large ionization potentials reported up till now have shown carrier mobilities that are smaller than that of pentacene. Here, we report on a new organic semiconductor, di(phenylvinyl)anthracene (DPVAnt), [9] that combines large carrier mobility (similar to that of pentacene) with increased ionization potential and improved stability as compared to pentacene. DPVAnt has been synthesized by a Suzuki coupling reaction between 2,6-dibromoanthracene and 4,4,5,5-tetramethyl-2-[2-phenylvinyl]-[1,3,2]dioxaborolane [9] with a yield of 85%.Pentacene has been purchased from Fluka. Both semiconductors have been purified by temperature gradient sublimation in a stream of inert gas. Cyclic voltammetry indicates a highest occupied molecular orbital (HOMO) energy of -5.4 eV for DPVAnt, as compared to -5.0 eV for pentacene. From UV-vis absorption spectroscopy we have determined an optical bandgap of 2.6 eV for DPVAnt and 1.8 eV for pentacene. These results are consistent with the general observation that molecules characterized by a smaller conjugated p-system have more negative HOMO energies and larger bandgaps.Simple TFT test structures have been prepared on heavily doped silicon substrates (serving as the gate electrode) with a thermally grown SiO 2 gate dielectric. The dielectric surface has been treated with octadecyltrichlorosilane (OTS), [10] and the organic semiconductor has been vacuum deposited onto the substrate. Gold source/drain contacts have been thermally evaporated through a shadow mask (Fig. 1a). During the deposition of the semiconductor, the substrates are held at a temperature of 60°C for pentacene and 80°C for DPVAnt. The carrier mobilities extracted from the transfer characteristics measured in air are 1 cm 2 V -1 s -1 for pentacene and 1.3 cm 2 V -1 s -1 for DPVAnt (Fig. 1b). Both TFTs have an on/off current ratio of 10 7 and a subthreshold swing of 500 mV decade -1. Perhaps the most striking differences between the two devices are the much more negative turn-on and threshold voltages of the DPVAnt transistor (V turn-on = -14 V, V th = -16 V) as compared to the pentacene TFT (V turn-on = -2 V, V th = -5 V). The exact reason for this difference is not known, but it may be related to the more negative HOMO energy of DPVAnt as compared to pentacene. As shown by the atomic force microscopy (AFM) images in Figure 1c and d, both semiconductors form well-ordered polycrystalline films, which is a prerequisite for obtaining large carrier mobilities.For practical applications, a transistor structure with patterned gate electrodes ...