A printing technology combining screen-printing with a wet-etching process for the gate electrodes of organic thin film transistors on a plastic substrate
We have developed a practical printing technology for the gate electrode of organic thin film transistors (OTFTs) by combining screen-printing with a wet-etching process using nano-silver (Ag) ink as a conducting material. An Ag film was deposited onto a PVP (polyvinylphenol)-coated PC (polycarbonate) plastic substrate by screen-printing with nano-Ag ink, where Ag content of 20wt.% was mixed using a terpineol solvent. Subsequently, the film was cured at 200C for 60min, and then finally wet-etched through patterned positive photo-resist masks. The screen-printed Ag electrode exhibited a minimum line width of ?5?m, a thickness of ?65nm, and a resistivity of ?10?6?cm, producing good geometrical and electrical characteristics for a gate electrode. Additionally, it also provided good step coverage with the PVP dielectric layer, and consequently leakage current between the gate and source/drain electrodes was eliminated. Moreover, the electrical characteristic of the screen-printed Ag electrode was not significantly changed even after a bending test in which the Ag electrodes were bent with a bending radius of 6mm and 2500 iterations of cyclic bending. OTFTs with the screen-printed Ag electrode produced a saturation mobility of 0.13cm2/Vs and a current on/off ratio of 1.79106, being comparable to those of an OTFT with a thermally evaporated Al gate electrode.
screen-printing wet-etching gate electrode organic thin film transistor (otft) nano-silver ink