Self-aligned organic field-effect transistors on plastic with picofarad overlap capacitances and megahertz operating frequencies

摘要

Using a combination of nanoimprint lithography, gate-source/drain self-alignment, and gravure and inkjet printing, we fabricate organic field-effect transistors on flexible plastic substrates with gate-source and gate-drain electrode overlap capacitances of C_(OL) ＜ 1 pF, equivalent to channel-width normalised capacitances of C*_(OL) = 0.15-0.23 pF mm~(-1). We compare photopatterned and nanoimprint lithography patterned channels of L ≈ 3.8 μm and L ≈ 800 nm, respectively. The reduction in L was found on average to result in order of magnitude greater switching frequencies. Gravure printing the dielectric (versus photo-patterning) was found to yield an order of magnitude lower overlap capacitance C*_(OL) = 0.03 pF mm~(-1), at the expense of greater processing variation. Inkjet printed p- and n-type polymeric organic semiconductors were used to fabricate organic-field effect transistors with a peak cutoff frequencies of f_S = 9.0 ± 0.3 MHz at V_(GS) = 30 V, and transition frequencies of f_T = 3.3 ± 0.2 MHz at V_(GS) = 30 V.