N , N ′ -dioctyl-3,4,9,10-perylene tetracarboxylic diimide (PTCDI-C8H) thin films have been implemented into organic thin-film field-effect transistors. Mobilities up to 0.6 cm2 V−1 s−1 and current on/off ratios >105 were obtained. Linear regime mobilities were typically half of those measured in the saturation regime. X-ray studies in reflection mode suggest a spacing of ∼20 Å for thin evaporated films of PTCDI-C8H, which is consistent with the value of ∼21±2 Å obtained from our simulations when an interdigitated packing structure is assumed.
them under vacuum at 55 C for 24 h. After drying, anhydrous toluene and the monomer (e-CL or PDX) were added sequentially using a syringe pump. The reaction mixture was stirred under an argon atmosphere at 55 C for 24 h. To remove any physisorbed polymers that were polymerized from hydroxyl-terminated impurities in solution or water the substrate was thoroughly washed and sonicated for 5 min. The solvent was 1,2-dichloroethane for PCL and 1,1,1,3,3,3-hexafluoro-2-propanol for PPDX, respectively. Prior to analysis, the substrate was further dried under reduced pressure at room temperature for 24 h.Instrumentation: Polarized IR external reflectance spectroscopy (PIERS) spectra were recorded on a Thermo Nicolet Nexus Fourier-transform infrared (FTIR) spectrometer in single reflection mode. The p-polarized light was incident at 80 relative to the surface normal of the substrate. A narrow band mercury±cadmium±telluride (MCT) detector was used. We averaged 1024 scans to yield the spectrum at a resolution of 4 cm ±1 . The sample compartment was purged with dry and CO 2 -free air. An ellipsometer (Gaertner L116 s) equipped with a He±Ne Laser (632.8 nm) was used to determine the thickness of the films. Contact angles were determined using a Phoenix 300 apparatus (Surface Electro optics Co. Ltd, Korea). Gel permeation chromatography (GPC) traces were obtained at room temperature by Waters 210 GPC. The concentration of polymer samples was 1.0 mg mL ±1 with a flow rate of 1.00 mL min ±1 and injection volume of 200 lL. XPS study was performed with a VG-Scientific ESCA-LAB 250 spectrometer with monochromatized Al Ka X-ray source. Secondaryion mass spectra were recorded by a PHI 7200 time-of-flight secondary ion mass spectrometer. AFM images were recorded using a Nanoscope IIIa apparatus (Veeco). We used tapping-mode AFM to image the polymer films. Organic semiconductors have attracted considerable interest for use as active channels in electronic and photonic devices, such as organic thin-film transistors (OTFTs), [1] photovoltaic cells, and light modulators. These materials are compatible with plastic substrates and thus are advantageous for lightweight, large-area electronics applications that require structural flexibility. Thin-film transistors with organic semiconductors as active channel material have made significant progress in the past decade and their utility in active matrix displays [1a,2±4] and integrated circuits [5±8] has been demonstrated. The technology that is believed to have the highest potential for minimizing the manufacturing cost of large-area electronics requires the use of soluble organic semiconductors, which include polymers, oligomers, and other small molecules, for solution deposition. This approach, combined with direct patterning techniques, such as large-area stamping, [4] screen printing, [9] and inkjet printing, [10] are very attractive and suitable for relatively low-resolution patterning in the range 25±100 lm. While higher-resolution (10±20 lm) inkjet printing has been demonstrated ...
This study describes the effect of covalent derivatization of source and drain electrodes with monolayers of organic semiconductors. These monolayers form a template on the metal surface and provide better electronic coupling between the electrode and the semiconductor. We see a large improvement in nanoscale (40-100 nm) transistors only when the monolayer presents functionality that is complementary to the chemical and electronic structure of the molecular semiconductor.
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