High-frequency organic field-effect transistors by low-cost direct-writing and printing techniques

摘要: Printed polymer electronics is paving the way to the development of portable, light-weight and distributed applications in the fields of wearables, healthcare, sensors and automation. A key point making this technology suitable for the realization of cost-effective products is the use of printing techniques, which offer the capability of depositing and/or patterning functional materials on large areas with high a throughput and at low cost. Despite impressive advancements in terms of charge mobility in polymeric semiconductors (in excess of 10 cm2/Vs), the maximum operational frequency of OFET devices is still limited, mainly due to the coarse patterning resolution offered by conventional low-cost printing techniques. To date, the achievement of operational frequencies in excess of 10 MHz, a generally acknowledged threshold for enabling many applications including the driving of high-resolution displays, has mainly relied on the use of complex photolithographic and/or evaporation techniques, undermining the cost-effectiveness concept. In this work we choose femtosecond-laser sintering as a direct-writing technique to realize high-resolution electrodes down to a minimum feature size of about 1 µm. We combine this technique with bar-coating, a large-area printing technique, to fabricate OFETs with a simple, fully mask-less, roll-to-roll compatible approach. The realized OFETs on a glass substrate feature a maximum transition frequency ft= 20 MHz, the highest ft reported to date for devices featuring printed polymers and direct-written electrodes. In addition to this result, demonstrated for n-type OFETs, we also prove that the fs-laser sintering …