Direct-printed organic thin-film transistor using PDMS stamp and low viscosity nanosilver ink.

The contact electrodes of printed organic thin-film transistors (OTFTs) were fabricated by direct printing using patterned hard poly(dimethylsiloxane) (h-PDMS) stamp with injection channel onto flexible poly(ethylenenaphthalate) (PEN) plastic substrates, wherein low-viscosity and low-resistance conductive nanoparticle silver (Ag) ink was injected. The source and drain electrodes (W/L = 500 microm/5 microm, 500 microm/10 microm, and 500 microm/20 microm) of printed OTFT were fabricated by direct printing. The printed OTFT with polyvinylphenol (PVP) as polymer dielectric layer was formed by spin coating and poly(3-hexylthiopene-2,5-dily) (P3HT) as organic semiconductor layer was ink-jet printing. The printed OTFT was characterized in air and the following parameters were obtained: a mobility of 0.06 (+/- 0.02) cm2/Vs, an on/off current ratio of 10(4) and a subthreshold slope of 2.53 V/decade. The direct printing using patterned h-PDMS stamp for ink injection patterning made it be possible to fabricate printed OTFT with a channel length as below as to 5 microm. The number of steps in the fabrication process was reduced by 20 steps compared with photolithography.