Stable, Evaporation Processed Organic Thin Film Transistors on Deformable Plastic Substrates
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2009 MRS Spring Meeting, San Francisco, USA
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Macroelectronic devices, such as flexible or conformable displays, plastic solar cells, smart cards, sensors, inverters, frequency information tags (i.e. inventory labels and price tags) etc. are impelling the emerging field of organic electronics. Materials employed for fabrication include not only small molecular semiconductors as pentacene or buckminsterfullerene, but also polymeric organic semiconductors favorable in organic solar cells. Beneficially, these soluble materials offer the possibility to be processed by cost-efficient roll-to-roll (R2R) printing technologies. However, as has been already demonstrated in packaging industry, R2R processing is also compatible with vapor deposition methods that generally apply to small organic molecules. While the latter ones can be purified to a high degree, polymers and solvents are more susceptible to incorporation of various types of ionic impurities, which in the case of organic field effect transistors may give rise to unwanted effects like bias stress and hysteresis. Therefore alternative routes for the production of high purity components in OFETs may arise interest. One of the possible avenues is the deposition of both the active semiconductor and the insulating dielectric layers by vapour deposition only, with the advantage that the evaporable materials generate a well defined interface with low trap densities when growth conditions are optimized. The present work deals with the development of organic field effect transistors consisting of commercially available materials: polyaniline and melamine as the organic insulators, fullerene (C60) as the organic semiconductor and aluminium for the patterned source and drain electrodes. All materials are vapour deposited from their solid phase on flexible poly(ethylene terephtalate) or deformable PDMS substrates.