In this work, the insulating properties of poly(4-vinylphenol) (PVP) and SU-8 (MicroChem, Westborough, MA, USA) dielectrics are analyzed and compared with each other. We further investigate the performance behavior of organic field-effect transistors based on a semiconducting liquid-crystal polymer (LCP) using both dielectric materials and evaluate the results regarding the processability. Due to the lower process temperature needed for the SU-8 deposition, the realization of organic transistors on flexible substrates is demonstrated showing comparable charge carrier mobilities to devices using PVP on glass. In addition, a µ-dispensing procedure of the LCP on SU-8 is presented, improving the switching behavior of the organic transistors, and the promising stability data of the SU-8/LCP stack are verified after storing the structures for 60 days in ambient air showing negligible irreversible degradation of the organic semiconductor.

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Abstract:We report on a micro-dispensing system for 6,13-Bis(triisopropylsilylethynyl) pentacene (TIPS-pentacene) to enable homogenous crystallization and uniform film morphology of the dispensed droplets using a two-solvent mixture along with the use of an insulating binder. This solution composition results in a controlled evaporation of the droplet in ambient air such that the Marangoni flow counteracts the outward convective flow to enable uniform radial crystal growth from the edge towards the center of the drops. The consequence of this process is the high degree of uniformity in the crystallization of the drops, which results in a reduction in the performance spread of the organic field effect transistors (OFET) created using this process. The addition of the insulating binder further improves the reduction in the spread of the results as a trade-off to the reduction in mobility of the transistors. The transfer curves of the OFETs show a tight grouping due to the controlled self-alignment of the TIPS-pentacene crystals; this repeatability was further highlighted by fabricating p-type inverters with driver to load ratios of 8:1, wherein the output inverter curves were also grouped tightly while exhibiting a gain of greater than 4 in the switching region. Therefore, the reliability and repeatability of this process justifies its use to enable large area solution-processed printed circuits at the cost of reduced mobility. OPEN ACCESSElectronics 2015, 4 566

In this paper, we report on a novel device that addresses the needs for an efficient, field deployable and disposable system in the field of bio-chemical sensors using organic semiconductors. The Fraunhofer Institute has enabled a complete roll-to-roll manufactured polymer-opto-chemical-electronic module on a foil substrate, wherein an electroluminescent light source has been hetero-integrated together with an organic TFT, working as a photo-detector. A chemically sensitive, colour changing film is sandwiched in between the two elements to form an optical detection system for volatile analytes such as amines. The setup, henceforth referred to as the "PolyOpto" module, comprises of a dye coated layer that can detect specific chemical reactions by colour change inserted in between the EL light source and the OTFT photo-detector. A hole is laser cut through the system to allow the sensor layer to come in contact with the gases, which then through a chemical reaction, chang es colour and initiates a different response in the output of the organic transistor. Hence, this allows for a disposable chemo-analytical system that can be used in various application fields. As compared to conventional systems, the advantage here lies in the direct integration of the different functionalities without any advanced assembly steps, simultaneous use of coatings for both components (transparent electrode and wiring layer) and roll-to-roll compatibility, thus rendering a disposable system. We believe that it aptly demonstrates the capabilities of polytronics in functional integration for low-cost bio-sensor manufacturing

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