Inkjet-Printed Silver Gate Electrode and Organic Dielectric Materials for Bottom-Gate Pentacene Thin-Film Transistors

An inkjet-printed silver electrode and a spin-coated cross-linked poly(4-vinylphenol)(PVP) dielectric layer were used as a gate electrode and a gate insulator for a bottom-gate pentacene thin-film transistor (TFT), respectively. The printing and the curing conditions of the printed silve electrode were optimized and testex on various substrates, such as glass, silicon, silicon dioxide, polyethersulfone, polyethyleneterephthalate, polyimide and polyarylate, to produce a good sheet resistance of 0.2 similar to 0.4 Omega/square and a good surface roughness of 2.38 nm in RMS value and 20.14 nm in peak-to-valley (P2V) value,which are very similar to those of conventionally-sputtered indium-tin-oxide (ITO) or thermally-evaportaed silver electrodes. The coated PVP layer of metal/PVP/metal devices showed a good insulation property of 10.4 nA/cm(2) at 0.5 mV/cm. The PVP layer further reduced the surface roughness of the gate electrode to provide a good interface to the pentacene layer. The pentacene TFT with a structure of glass/printed silve/PVP/pentacene/ Au shoed a good saturation region mobility of 0.13 cm(2)/Vs and a good on/off ratio of larger than 10(5), which are similar to the performance of a pentacene TFT with a conventional ITO gate electrode.