The performance of organic thin-film transistors (OTFT) for flexible, low cost and disposable "plastic" electronic products advances rapidly: various organic semiconductors display hole or electron carrier mobilities [1] that compare favorably with those of hydrogenated amorphous silicon, [2] the inorganic counterpart for such applications as flexible displays, [3,4] smart cards and radio frequency identification tags, [5,6] nonvolatile memories [7] and sensors. [8,9] The possibility for tailoring functional organic materials, bears potential towards novel electronic products such as smart skins, [10] smart textiles [11] and "invisible electronics", [12] where multiple functionalities, portability and ubiquitous integration is requested. In this context diverse properties of organic thin-film devices are inevitable such as lightweight, low power consumption, low operationvoltage and compatibility with diverse substrates.[12]Reducing the threshold voltage and the subthreshold swing is essential for operating OTFTs at low-voltage levels. When combined with very low gate leakage currents, OTFTs may also become a key element in high-end sensor applications, such as flexible touch pads and screens or thermal imaging tools for night vision, surveillance or for the detection of undesired heat loss paths in buildings.The aforementioned transistor parameters not only critically depend on the thickness and the dielectric properties of the gate insulator, [12][13][14] but also on the trapped charge densities at the interface between these materials. The selection of semiconductors and gate insulators with excellent interface properties is currently the challenge in the quest for improving the performance of OTFTs.Here we show that bottom-gate OTFTs based on the organic semiconductor pentacene and high-k nanocomposite gate dielectrics, exhibit transistor performances with very low gate leakage currents, subthreshold swings close to the theoretical limit, and low-voltage battery operation. The subthreshold swings of OTFTs with different organic and hybrid gate dielectrics follow an inverse dependence on the gate capacitance as is expected by standard MOS theory. The trapped charge carrier density at the interface between the semiconductor and the dielectric surpasses that of the SiO 2 -pentacene interface, being close to the average trap densities in the SiO 2 -Si interface in metal oxide semiconductor transistors. [15] We also report the first application of these OTFTs in an optothermal light sensor. We describe the transistor, the temperature sensitive fluorinated polymer, their combination in an integrated circuit, and the application of this circuit as a thermal infrared sensor and as a switch that can be operated by a laser pointer. Figure 1 shows the structure of low-voltage organic transistors with high dielectric constant (high-k) oxide-polymer nanocomposites. Al 2 O 3 or ZrO 2 were chosen as high-k dielectric materials, combined with poly(a-methyl styrene) (PaMS) or poly(vinyl cinnamate) (PVCi) to form a smooth and ...

We report on the natural source based and biodegradable material cellulose on Al2O3 as ultrathin hybrid high-k dielectric layer for applications in green electronics. Dielectric films of 16 nm cellulose (ε ≈ 8.4) and 8 nm Al2O3 (ε ≈ 9) exhibit low leakage currents up to electric fields of 1.5 MV/cm. Pentacene and C60 based organic thin film transistors show a well-balanced performance with operation voltages around 2 V. They are implemented in complementary inverters with excellent switching behavior, a small-signal gain up to 60 and with exceptionally high and balanced noise margin values of 82% at ultralow operation voltage (VDD = 2.5 V).

Here we report on the fabrication and characterization of ultra-thin nanocomposite layers used as gate dielectric in low-voltage and high-performance flexible organic thin film transistors (oTFTs). Reactive sputtered zirconia layers were deposited with low thermal exposure of the substrate and the resulting porous oxide films with high leakage currents were spin-coated with an additional layer of poly-alpha-methylstyrene (P alphaMS). After this treatment a strong improvement of the oTFT performance could be observed; leakage currents could be eliminated almost completely. In ellipsometric studies a higher refractive index of the ZrO(2)/P alphaMS layers compared to the "as sputtered" zirconia films could be detected without a significant enhancement of the film thickness. Atomic force microscopy (AFM) measurements of the surface topography clearly showed a surface smoothing after the P alphaMS coating. Further studies with X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) also indicated that the polymer definitely did not form an extra layer. The polymer chains rather (self-)assemble in the nano-scaled interspaces of the porous oxide film giving an oxide-polymer "nanocomposite" with a high oxide filling grade resulting in high dielectric constants larger than 15. The dielectric strength of more than 1 MV cm(-1) is in good accordance with the polymer-filled interspaces.

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