This PDF file contains the front matter associated with SPIE Proceedings Volume 7417, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

The development of suitable materials for organic electronics is still one of the key points to access new application areas with this promising technology. Semiconductors based on thiophene chemistry show very high charge carrier mobilities. The functionalization with linker groups provided materials that built monomolecular layers of the semiconductors on the hydrolyzed oxide surface of a silicon-wafer. This approach lead to self-assembled mono-layer field-effect transistors (SAM-FETs) with mobilities of up to 0.04 cm²/Vs, which is comparable to the values of the respective bulk thin film. Transparent inorganic conductors like ITO are highly conductive but the costly processing and the brittleness hamper their use in cost-sensitive and/or flexible devices. Highly conductive PEDOT-grades have been developed with conductivities of up to 1000 S/cm which are easily applicable by printing techniques and can be used as ITO replacement in devices such as touch panels or organic photovoltaics.

The search of new organic molecules with improved properties is of fundamental relevance for hybrid organic-inorganic based devices (OLED, FET, PV, injection layers, flexible large area devices, lasers, etc.). Triindole based materials present extended aromatic cores with disk-like geometry that allow tailoring their electronic properties through chemical functionalization. In this work we present an optical and electronic study of new triindole based single crystals. Pistacking gives rise to highly ordered columnar structures yielding to high mobilities, around 0.4 cm²V^-1s^-1. External oxidation is found to increase orders of magnitude the conductivity. Slight modifications of this platform modify substantially the crystallization dynamics and therefore the quality of the thin films obtained by spin coating from solutions with different solvents. The morphology, stability and properties of the optimized films are found to be promising for device fabrication. A comparative study of the absorption and emission efficiency of solutions and thin films of the different derivatives is presented. The first tests for OLED and OFET devices are under way.

We have studied alkyl-substituted pentacene derivatives for solution-processing. By incorporation of substituent(s), enhancement of solubility depending on substituted position(s) and substituent(s) was confirmed. Solution-processed films of the derivatives showed highly oriented crystals with herringbone structure. This indicates that molecular aggregation and electronic structure have been preserved after the substitution as expected from molecular design. Thinfilm transistors of the derivatives exhibited large carrier mobility above 1cm²/Vs.

A family of conjugated polymers with fused structures consisting of three to five thiophene rings and with the same alkyl side chains has been synthesized as a means to understand structure - property relationships. All three polymers showed well extended conjugation through the polymer backbone. X-ray diffraction study of the polymer thin films suggests that the polymer with the even number of fused thiophene rings forms a tight crystalline structure due to its tilted side chain arrangement. On the other hand, the polymers with the odd number of fused thiophene rings packed more loosely. Characterization in a field-effect transistor configuration showed that the mobility of the polymer with the even number of rings is one order of magnitude higher than its oddnumbered counterparts. Through this structure - property study, we demonstrate that proper design of the molecules and properly arranged side chain positions on the polymer backbone can greatly enhance polymer electronic properties

We fabricated an organic thin film prepared by oligomers of organic material according to the solution method and examined the quality of thin film using an X-Ray diffractometer. Based on the results, we fabricated flexible-organic field effect transistors using the spin-coating method. We adopted a polyethylenenaphthalate (PEN) film as the substrate, a cross-linked poly-4-vinylphenol (PVP) thin film as the gate dielectric insulation layer and a soluble quaterthiophene layer or pentacene layer as an active layer. The carrier mobility of the prepared quaterthiophene- organic-field effect transistor, the threshold voltage and the ON/OFF ratio are 2.27×10^-3 cm²/Vs, -37V and -37V respectively. In soluble Pentacene-OFET, the mobility is 0.09cm²/Vs, the ON/OFF is about 10² and the threshold voltage (Vth) is -7V.

It has been well established that in organic thin film transistors (OTFTs), charge transport occurs within the first few monolayers of the semiconductor at the semiconductor/dielectric interface. Understanding and engineering the semiconductor-dielectric is therefore critical. Large discrepancies in performance, even with seemingly identical surface treatments, indicate that additional surface parameters must be identified and controlled in order to optimize OTFTs. Here, we used the Langmuir-Blodgett technique to study the effect of an octadecylsilane dielectric modification layer on OTFT performance. We found a crystalline, dense OTS monolayer promotes two-dimensional growth in a variety of organic semiconductors. Mobilities as high as 5.3 cm²/Vs and 2.2 cm²/Vs were demonstrated on crystalline OTS for C₆₀ and pentacene, respectively. Finally, we also developed a simple, scalable spin-coating method to produce crystalline OTS. This work represents a significant step towards a general approach for morphological control of organic semiconductors which is directly linked to their thin film transistor performance.

Much effort is being dedicated to develop small organic molecules for their use in organic electronic devices, for which a key parameter is the mobility of charge within the active organic layers. Important advances achieved in this field have been therefore connected to the enhancement of the charge carrier mobility of organic semiconductors. In this communication we present a new family of stable high-mobility organic p-type semiconductors based on the electronrich 10,15-dihydro-5H-diindolo[3,2-a:3',2'-c]carbazole (triindole) platform. We show how it is possible to tune their electronic properties as well as their supramolecular organization through chemical functionalization.

We successfully fabricated 4.7-inch organic thin film transistors array with 320×240 pixels on flexible substrate. The mobility, ON/OFF ratio, subthreshold swing and threshold voltage of OTFT on flexible substrate are: 0.015 cm2/V-s, 1.1 V/dec, 10E6 and -3.2 V. After laminated Sipix electrophoretic media on OTFT array, a panel of 4.7 inch 320×240 OTFT-EPD was fabricated. All of process temperature in OTFT-EPD is lower than 130 . The pixel size in our panel is 300 μm × 300 μm, and the aperture ratio is over than 50 %. The OTFT channel length and width is 20 μm and 200μm, respectively. The operation voltages used on the gate bias is -30 V during the row data selection and the gate bias are 0 V during the row data hold time. The data voltages used on the source bias are -20 V, 0 V, and 20 V during display media operation.

A full-color, top-emission active-matrix organic light-emitting diode display build on a flexible substrate (flexible OLED) has been successfully driven by organic-TFTs made by a scalable manufacturing process (lift-off and shadow mask free process). The OTFTs were fabricated with low cost metal (copper and aluminum) electrodes. The backplane architecture was developed at low temperatures (<150°C) with solution-processed organic dielectrics. The fabricated TFTs are reliable against bending stress with 2-mm radius. With this ultra high flexibility of the OTFT, the display shows no significant degradation for an operating period >25 hours with more than 10,000 times bending.

Reduction in the operating voltage of organic field-effect transistors (OFETs) is sought for their successful implementation into future portable and low-power electronic applications. Here we demonstrate OFETs with operation below 2 V enabled by the use of self-assembled monolayer (SAM) gate dielectrics with high geometrical capacitances. A high surface energy monolayer is chosen to allow processing of small molecule semiconductors from solution. Impedance spectroscopy measurements of metal-insulator-semiconductor devices suggest the geometrical capacitance of the alumina-SAM dielectric can reach ~1 μF/cm² when accumulating charge at the semiconductor-insulator interface. Atomic force microscopy images reveal that the glass substrates and the SAM-functionalized aluminum gate electrode display significant roughness. Despite this, mobilities of 0.02 cm²/Vs are demonstrated. These results represent an important step towards low-power solution processable electronics.

Taking another step towards industrial production of devices based on organic semi-conductors, this work presents an extension of the organic vapor phase deposition technique to in-line geometry. A study of the in-line tool operation is carried out. It leads to the definition of a specific in-line deposition rate that qualifies the coating speed. It also allows for an understanding of processing parameter variations that lead to high deposition speeds. As a consequence, pentacene films are grown at in-line deposition rates of up to 1055μm²/s. This corresponds to web speeds of 2.1 m/min, equivalent to an average deposition rate of 105 Å/s in a static system. These films present a high uniformity, with a thickness standard deviation below 1.2% over 4 inch diameter substrates. Moreover, with transistor mobilities of up to 1.5 cm²/Vs, these pentacene films are of excellent electrical quality. This quality is conserved up to the highest deposition rates. Finally, 5-stage ring oscillators on foil based on a pentacene thin film deposited by in-line OVPD achieve a frequency of 24 kHz at a supply voltage of 20 V.

Self-assembled monolayers (SAMs) of alkyl silane compounds have been used for modifying gate dielectrics surface of organic field-effect transistors (OFETs) and they have frequently shown improvement of FET performances. In this paper we deposited alkyl silane SAMs by simple spin-coating technique onto Si/SiO2 substrates. Spin-cast octadecyltrimethoxysilane (OTMS) SAMs had ultra smooth crystalline surface and provided an excellent dielectric surface for OFETs. In fact on the OTMS SAM treated dielectric, pentacene OFETs showed hole mobilities over 2.0 cm²/Vs and electron mobilties over 1.0 and 5.0 cm²/Vs were demonstrated for 3,4:9,10-perylene diimide derivative and C60, respectively. Fabrication technique and characterizations of the OTMS SAMs is described.

Conducting and semiconducting polymers are important materials in the development of printed, flexible, large area electronics such as flat panel displays and photovoltaic cells. There has been rapid progress in developing conjugated polymers with high transport mobility required for high performance field effect transistors (FETs), beginning with mobilities around 10^-5cm²/Vs to a recent report of 1cm²/Vs for poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno [3,2-b]thiophene) (PBTTT). In this work, the electrical properties of PBTTT are studied at high charge densities both as the semiconductor layer in FETs and in electrochemically doped films to determine the transport mechanism. We show that data obtained using a wide range of parameters (temperature, gate-induced carrier density, source-drain voltage and doping level) scale onto the universal curve predicted for transport in the Luttinger Liquid description of the onedimensional "metal", where fermions along the 1D chain collectively behave as bosons, and where charge and spin are decoupled.

We used the p-channel pentacene and n-channel PTCDI-C₁₃H₂₇ thin film transistors (OTFTs) to compose an organic complementary inverter device. In the experiment this device was inserted a polyimide (PI) layer into the interface of a semiconductor and gate insulator to improve the orientation phase and decrease the leakage current for n- and p-type OTFTs simultaneously. The hysteresis behavior of the transistors and inverters exhibited high trapping and detrapping speeds for the traps between gate dielectric and semiconductor layers; therefore, the PI layer had functions for improving surface roughness and reducing the hysteresis behavior of gate-dielectrics. The hysteresis of pentacene and PTCDI-C₁₃H₂₇ films with PI layer was smaller than that without PI obtained by capacitance-voltage measurements. Therefore, the p-type and n-type OTFTs with PI as modification layer had high field-effect mobility of 0.976 and 0.512 cm²V^-1s^-1, on/off ratio of 1.7×105 and 7×104, threshold voltage of -10.76 and 12.21 V, respectively; by contrast, poor performance occurred in the device without PI layer. Additionally, a good performance for the organic inverter was achieved when pentacene and PTCDI-C₁₃H₂₇ films grown on the PI layer exhibited the match of surface energy between the semiconductor and PI and the large grain size. An organic complementary metal oxide semiconductor (O-CMOS) device had similar drain current, threshold voltage and mobility for n-type and p-type transistors by using the PI layer as surface modification of the dielectric layer. Compared with the device without the PI layer, there were higher noise margins and gains and lower power dissipation of the O-CMOS.

For application of device fabrication by inkjet printing, an accurate and high resolution patterning method is required. However, high resolution inkjet printing, which limited by the inkjet nozzles and the ink movements, is one of the most challenging issues at present. An enhanced control of ink flow and spread by surface energy patterning on substrates can be used to improve the resolution and quality of the inkjet printed devices. Our strategy is depositing a hydrophobic pattern on a hydrophilic substrate, and thereafter inkjet printing the functional ink on top of the surface energy pattern. High surface energy contrast patterns on polyimide were got by microcontact printing, which can make ink moving from hydrophobic area to hydrophilic polyimide substrate. Inkjet printed silver patterns with 15 μm thin gaps were obtained by the surface energy pattern. This visible and easy processing pattern can be used widely in inkjet printing for higher resolution, more precise pattern, and smaller devices.

In this article, we fabricated a series of different geometries for pentacene based thin film transistors (TFTs), including top contact (TC) and bottom contact (BC) configurations, to monitor variations in characteristics. The threshold voltage (Vth) in the saturation regime shifted toward a positive voltage, i.e., from 0.5, 3.2, 9.1, 12.1, and 19.5 V for the channel lengths 67, 47, 23, 19, and 15 μm, respectively, in BC TFTs. All of the TFTs were operated in depletion mode. However, the Vth in the linear regime shifted from -9.3, -9.0, -3.8, -1.8, and 1.5 V for the same devices. Most of the TFTs in the linear regime were operated in enhanced mode. The phenomenon is believed to be strongly correlated with the longitudinal electric field (VDS/L). The high VDS induces a high carrier injection, which makes the pentacene TFTs behave like a depletion type transistor. This assumption is evidenced by the low carrier injection with small VDS results. The device configuration and space charge region must be discussed in more detail. Furthermore, the field effect mobility variation and structure configuration effect is discussed in more detail within the full manuscript.