Thin-film transistor (TFT) backplanes fabricated by using jet printing as the only patterning method are reported. Additive and subtractive printing processes are combined to make 128×128 pixel active matrix arrays with 340μm pixel size. The semiconductor used, a regioregular polythiophene, poly[5,5′-bis(3-dodecyl-2-thienyl)-2,2′-bithiophene]; (PQT-12) is deposited by inkjet printing and exhibits average TFT mobility of 0.06cm2∕Vs, on/off ratios of 106, and minimal bias stress. The printed TFTs have high yield with a narrow performance distribution. The pixel design benefits from the registration accuracy of jet printing and it is shown that the electrical performance is suitable for addressing capacitive media displays.

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The electronic transport and the device properties of pentacene thin film transistors are reported, showing the influence of the dielectric on the structural and transport properties. The structure and morphology of pentacene films on organic and inorganic dielectrics were compared by x-ray diffraction measurements and atomic force microscopy. For the investigated dielectrics we observed a clear correlation between the morphology and the structural properties of the highly polycrystalline films. In the case of inorganic dielectrics the roughness of the dielectric has a distinct influence on the morphology and the structural properties, whereas the films on organic dielectrics bonding between pentacene and the dielectric may have an influence on the growth mechanism. We find that careful control of the deposition conditions give films with similar transport properties on organic and inorganic dielectrics. To study the electronic properties we have realized inverted staggered transistors. The TFTs exhibit mobilities of ~0.4 cm 2 /Vs and on/off ratios of 10 8 on organic and inorganic dielectrics. The influence of the dielectric on the device mobility, threshold voltage and sub-threshold voltage slope are discussed.

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