Organic electronics open new fields of applications requiring large-area coverage, structural flexibility, low-temperature and low-cost processing. A key for this technology is access to suitable materials. Progress in conducting and semiconducting materials for organic electronics will be reported. Highly conductive PEDOT-grades have been developed for high resolution printing. Linear oligomeric and star shaped oligothiophenes will be discussed. These materials show outstanding carge carrier mobility and environmental stability when deposited from vacuum deposition. After fine tuning the deposition parameter by ink jet printing we also obtained transistors with excellent properties. The concept of "flexible core" star shaped oligothiophenes will be discussion which might be a way to combine both, high charge carrier and wet processing.

A series of soluble pentacene precursors are designed, from which pure pentacene can be generated either thermally or photochemically. Small volatile fragments like CO and CO₂ are extruded during the dissociation reactions. Thin films of pentacene made from these precursors exhibited typical OTFT characteristics.

The structural and transport properties of evaporated fluorinated copper phthalocyanine organic field effect transistors with polymer dielectric layer polycarbonate were reported. A high field effect mobility of 5.7×10^-3 cm²/ Vs, an on/off ratio of 10⁴ and a threshold voltage of 5V were obtained under atmospheric conditions. χ-ray diffraction and atomic force microscopy show a clear correlation between the morphology and structure of F₁₆CuPc film on the polycarbonate dielectric surface. Temperature dependent measurements of the mobility were performed. X-ray diffraction results show that the crystallinity and orientation of F₁₆CuPc on polycarbonate thin film are enhanced with increasing surface temperature.

There has been a considerable interest on forming ambipolar organic thin film transistors (OTFTs) because such devices are advantageous for integrated circuits, such as lower power consumption, design and fabrication simplification, and better immunity. Most recently, Shi et al. observed a substantial mobility improvement in ambipolar OTFTs based on the heterojunction formed between copper-hexadecafluoro-phthalocyanine (F₁₆CuPc) and 2,5-bis(4-biphenylyl) bithiophene (BP2T). Specifically, the hole and electron mobility are improved by 3 and 12 folds from the bulk values, respectively. We examined the interface formation between F₁₆CuPc and BP2T using ultraviolet photoemission (UPS) and inverse photoemission spectroscopy (IPES). It is observed that in F₁₆CuPc/BP2T the heterojunction is characterized by band bending in both materials, while in BP2T/F₁₆CuPc the band bending is confined in BP2T only. For F₁₆CuPc/BP2T, the band bending of BP2T and F₁₆CuPc are 0.40 and 0.35 eV, respectively. The band bending region is ~15 nm in both materials, from which the Debye lengths of the materials can be deduced. The combination of the band bending and finite Debye lengths offers an explanation to the observed improvement and thickness dependence of the mobility in OTFTs based on such heterojunctions.

Pentacene-based organic superlattice transistors (OSLFETs) using the monolayer (ML) thickness of organic pentacene and amorphous organic material have been studied. By changing the unit number of pentacene (2 ML) and amorphous organic layers, transistor characteristics, namely, mobility, threshold voltage and on-off ratio, were markedly changed. Under optimum stacked layer conditions, the mobility was determined to be 1.35 cm²/Vs, and the on-off ratio, 10⁶. By changing the unit number of pentacene and amorphous organic layers, the sheet charge was determined to be 6.2×10¹¹ cm^-2. This superlattice configuration concept is expected to improve carrier transport and control the threshold voltage for an integrated circuit configuration.

Methods used to deposit and integrate solution-processed materials to fabricate thin film transistors by ink-jet printing are presented. We demonstrate successful integration of a complete additive process with the fabrication of simple prototype TFT backplanes on glass and on flexible plastic substrates, and we discuss the factors that make the process possible. Surface energy control of the gate dielectric layer allows printing of the metal source-drain contacts with gaps as small as 10 um as well as the polymer semiconductor whose electronic properties are very sensitive to surface energy. Silver nanoparticles are used as gate and data metals, and a polythiophene derivative (PQT-12) is used as the semiconducting layer, and the gate dielectric is a polymer. The maximum processing temperature used is 150°C, making the process compatible with flexible substrates. The I_ON/I_OFF ratio is 10⁵-10⁶, and TFT mobilities of 0.05 cm²/Vs were obtained. The electrical stability of the all-printed transistors was compared to conventional fabrication methods and it is shown to be acceptable for array operation. Here we discuss the yield of the printing process and show arrays that are integrated with E-ink media to form flexible paper-like displays.

We successfully fabricated 5-inch organic thin film transistors array with 320×240 pixels on flexible substrate. All the processes were done by photolithography, spin coating and ink-jet printing. The OTFT-Electrophoretic (EP) pixel structure, based on a top gate OTFT, was fabricated. The mobility, ON/OFF ratio, subthreshold swing and threshold voltage of OTFT on flexible substrate are: 0.01 cm²/V-s, 1.3 V/dec, 10E5 and -3.5 V. After laminated the EP media on OTFT array, a panel of 5 inch 320×240 OTFT-EPD was fabricated. All of process temperature in 10×10 OTFT-EPD is lower than 150 . The pixel size in our panel is 300 μm × 300 μm, and the aperture ratio is 50 %. The OTFT channel length and width is 20 μm and 200μm, respectively. We also used OTFT to drive EP media successfully. The operation voltages that are used on the gate bias are -30 V during the row data selection and the gate bias are 0 V during the row data hold time. The data voltages that are used on the source bias are -20 V, 0 V, and 20 V during display media operation.

Vertical phase separation of organic semiconductor/dielectric polymer blends has been used in field-effect transistors (FETs) to fabricate low-voltage devices, improve environmental stability, and reduce semiconductor cost. However, all structures reported in previous studies are dielectric-up and semiconductor-bottom structures, and it is difficult to combine multi-advantages in one system because special materials and methods are used in each case. Here, we first fabricated a semiconductor-top and dielectric-bottom bilayer structure by surface-induced vertical phase separation of conjugated molecules and insulating polymer blends. The use of these bilayered blends as active layer in FETs leads to an improvement of the device performance with a drastic reduction of semiconductor content because insulating polymer layer can act as modifier at the semiconductor/dielectric interface. Moreover, because the insulting polymer layer can be used as dielectric layer without any other dielectrics, the blended films can be used to fabricate high-performance, lowsemiconductor-content, and low-voltage FETs in a one-step process.

Molecular redox dopants are tested concerning their application to organic thin-film transistors (OTFT). Here we report on the feasibility of solution processing of molecular-doped transport layers, showing high air-stability of solutions and layers. We apply capacitance spectroscopy to investigate the interface of intrinsic and electrically doped layers. We also show that there is virtually no dopant migration in real devices, even when high electric fields up to 300 kV/cm² are applied for 1000 h. We report on p- and n-type on OTFTs with silver contacts. The application of injection layers based on redox dopants improves the measured field-effect mobility by about 2 orders of magnitude.

We have developed a flexible full-color OLED display driven by pentacene organic TFTs (OTFTs) with bottom-gate bottom-contact configuration. We will discuss an integration process of the display and improvement of stability by selective treatment of interfaces in the OTFTs. We have developed selective treatment of the surface of poly (vinyl-phenol) gate insulator using the selective growth of poly(p-chloroxylylene) after S/D electrode formation. This treatment has reduced deep carrier-trap density at semiconductor/gate insulator interface and has drastically suppressed bias-stress instability of the OTFTs. Direct carrier-injection structure with selective tiole treatment of S/D electrodes has been also developed. This suppresses the degradation of the OTFT due to increase of contact resistance in the integration. These techniques are promising for reliable display applications.

Organic transistor technology has been the subject of intense research in the last decade paving the way for industrialization of organic electronics applications characterized by low fabrication costs, additive manufacturing processes at low-energy, high flexibility and application versatility. A dedicated technology platform has been developed at ST and fully characterized, which is devoted to the manufacturing of all-organic transistor devices with sub-micron feature size as multilayered structures, obtained through a sequential combination of deposition from solution and patterning steps through stamps. The design and manufacturing platform is actually being assessed through the development of the first all-organic 'reduced complexity' microprocessor. An outline of the architecture and major building blocks will be presented.

We have successfully fabricated organic thin-film transistors (OTFTs) on plastic substrates by the printing process. The semiconductor of the OTFT was defined by inkjet printing. The poor consistency of the printing patterns has made high uniformity of the OTFTs more difficult to achieve. Thus, a basic unit of circuits called a transistor array with redundant transistors was designed and fabricated. In addition, we proposed a method to increase the circuit yield by incorporating a pre-testing step during circuit fabrication. These devices were then connected via printed nano-silver to each other to form a subcircuit called a gate. To verify the design flow, we measured the bootstrap inverters based on the transistor arrays. A ring oscillator was fabricated in a similar methodology based on the gate array.

We have fabricated polycrystalline thin films of liquid crystalline oligothiophene derivatives of ω, ω'-dioctylterthiophene (8-TTP-8) and ω, ω'-dihexylquarterthiophene (6-QTP-6). In order to evaluate carrier transport properties of the polycrystalline films in lateral and vertical orientations, we measured them by time-of-flight (TOF) experiments with sandwich type of liquid crystal cells and evaluating device performances of thin film transistors (TFTs) fabricated on SiO₂/Si, respectively. Because of the liquid crystallinity, we could observe non-dispersive transient photocurrents in polycrystalline films of 8-TTP-8 in spite of thick sample of 16 μm, and determine hole mobility to be 0.3 cm²/Vs. Because of the same reason, in spin-coated thin film of 8-TTP-8, where 8-TTP-8 molecules sit perpendicular to the substrate, the field effect transistor (FET) mobility was successfully determined to be 0.1 cm²/Vs. In the same way, we have obtained the TOF and FET mobility for 6-QTP-6 to be 0.03 and 0.04 cm²/Vs, respectively. On the basis of the present results, we discuss the benefits of the liquid crystallinity in fabricating polycrystalline films as an organic semiconductor for device applications.

In this study, device characterization and carrier transport properties of n-type fluorinated copper phthalocyanine (F₁₆CuPc) organic thin-film transistors (OTFTs) were investigated using bottom gate device configuration with oxygen plasma-treatment indium-tin-oxide (ITO) bottom source and drain (S/D) contact. We fabricated F₁₆CuPc-based OTFTs having comb-shaped channels with a series of channel lengths of 5~100 μm at a fixed channel width. The electrical characteristics of OTFTs were measured by a Keithley 4200-SCS semiconductor parameter analyzer in a dark glove box in a nitrogen atmosphere to avoid the influence of measuring environments. The device characteristics were analyzed using the charge-sheet metal-oxide-semiconductor field-effect transistor model equation. We found that both the linear and saturation field-effect mobilities and threshold voltages of F₁₆CuPc-based OTFTs increased with increasing channel length. The linear and saturated field-effect mobilities were gate-bias dependent in all devices with different channel dimensions. Moreover, the contact resistance between ITO S/D electrodes and F₁₆CuPc and channel resistance of F₁₆CuPc were investigated using the gated-transfer length method. The results of our experiments suggest that the contact resistance between ITO electrodes and F₁₆CuPc plays an important role in current-voltage characteristics. Additionally, abnormal increases in saturated field-effect mobility at channel lengths below 10 μm were observed in our experimental devices and were attributed to short channel effects. Such non-ideal effects of the present F₁₆CuPc-based OTFT devices were investigated in detail. In summary, we found that the oxygen-plasma-treatment ITO bottom contact S/D electrode-based F₁₆CuPc OTFT devices were very durable and suitable to make large area transistor arrays with complicated integrated circuits by photolithography techniques.

We show here that an array of random network of carbon nanotubes coated with non-polymeric organic materials and conjugated with pattern recognition algorithms has a high potential for diagnosis of lung cancer via breath samples. The results indicate that the sensors array allow excellent discrimination between the volatile organic compounds (VOCs) found in the breath of patients with lung cancer, relative to healthy controls, especially if the sensors array is preceded with either water extractor and/or pre-concentrator of VOCs.

A simple refractometer/photometer is described which uses a vacuum-deposited multilayer organic light emitting diode (OLED) light source and a vacuum-deposited planar heterojunction organic photovoltaic (OPV) detector, separated from each other on a thin glass attenuated total reflectance (ATR) element by 1-2 cm. A portion of the light output from the OLED light source is internally reflected in the ATR element, and the evanescent field from this internally reflected light interacts with solutions of variable refractive index in the region between the OLED and OPV. We document here the simple construction principles for devices of this type, and the characterization of the operation of this first-generation device in terms of i) photocurrent in the OPV detector versus light output from the OLED and ii) the response of the device to solutions of differing refractive index. In these first-generation devices we estimate a sensitivity to changes in refractive index of +/- of 10^-3 units.

With the goal of developing microfluidic platforms for sensing applications, flash-free micro patterns were embossed in polypropylene surfaces with ultrasonic heating for a biosensing lab-on-CD application. The embossed features were designed to act as reservoirs, valves, and reaction chambers to allow, in combination with a compact sensing platform, the monitoring of analyte levels using a standard PC-CD player. To generate the compact sensor, as an example, we chose the photoluminescence (PL)-based detection of lactate and glucose using an OLED-based sensing platform. Once embossed, the surface energy of the plastic substrate was chemically modified to make it hydrophilic. Reagents, placed in separate reservoirs, were directed through burst valves towards a reaction chamber via CD rotation. Lactate or glucose were monitored by measuring the effect of the related dissolved oxygen level on the PL decay time of an oxygen-sensitive dye, following analyte oxidation catalyzed by a suitable specific oxidase enzyme. The results demonstrate the potential of integrating OLEDs as excitation sources in PL-based sensors with microfluidic CD-based platforms, including for simultaneous multiple analyses.

Sensors based on organic electronic devices are emerging in a wide range of application areas. Here we present a sensor platform using organic light emitting diodes (OLED) and organic photodiodes (OPD) as active components. By means of lamination and interconnection technology the functional foils with OLED and OPD arrays form an in-plane optical sensor platform (IPOS). This platform can be extended with a wireless data and signal processing unit yielding a sensor node. The focus of our research is to engage the node in a healthcare application, in which a bandage is able to monitor the vital signs of a person, a so-called Smart Bandage. One of the principles that is described here is based on measuring the absorption modulation of blood volume induced by the pulse (photoplethysmography). The information from such a bandage could be used to monitor wound healing by measuring the perfusion in the skin. The OLED and OPD devices are manufactured on separate foils and glass substrates by means of printing and coating technologies. Furthermore, the modular approach allows for the application of the optical sensing unit in a variety of other fields including chemical sensing. This, ultimately enables the measurement of a large variety of physiological parameters using the same bandage and the same basic sensor architecture. Here we discuss the build-up of our device in general terms. Specific characteristics of the used OLEDs and OPDs are shown and finally we demonstrate the functionality by simultaneously recorded photoplethysmograms of our device and a clinical pulseoximeter.

A prototype of mechanically flexible photosensor arrays using organic bulk heterojunction photodiodes has been developed on plastic substrates. The integration of a 4 μm thick sensor layer onto a flexible amorphous silicon thin-film transistor backplane gave an image sensor array with 35% external quantum efficiency and noise equivalent power of 30 pW/cm² at reverse bias voltage of -4 V. Sensor properties such as sensitivity and spatial resolution are determined and compared to those of amorphous silicon photodiodes.