Flexible Pentacene Thin Film Transistors with Cyclo-Olefin Polymer as a Gate Dielectric

Flexible pentacene thin film transistors were fabricated and characterized with a hydroxyl-free and amorphous low-k cyclo-olefin polymer (COP) as a gate dielectric. The maximum processing temperature was 60 °C. The spin-coated COP thin films had excellent electrical insulating properties, and the pentacene TFTs showed negligible current hysteresis, a field-effect mobility of 1.60 cm2 /Vs, a subthreshold swing of 0.56 V/decade and an on/off ratio of > 106. Furthermore, a small threshold voltage shift below 1.83 V was obtained despite unpassivation of the pentacene layer after a gate bias stress of 104 s. These excellent air stabilities were attributed to the insulator with hydroxyl-free and low water absorbency.