Improvement of Performance of Organic Thin-Film Transistors through Zone Annealing

A zone annealing process is adopted to improve the performance of pentacene organic thin film transistors. The process is completed in a glove box full of dry nitrogen gas and with a heating wire (Ф0.1mm tungsten wire) inside. The device have the structure of glass/ITO (150nm)/Ta₂O₅ (60nm)/pentacene (60nm)/Au (20nm). Under the gate--source voltage -60V and the drain--source voltage -60V, the source--drain current, the mobility, and the on/off current ratio increase from 4×10^-7A to 2.0×10^-6A, 2.9×10^-3cm²V^-1s^-1 to 1.6×10 ²cm²V^-1s^-1, and 2×10³ to 5.33×10³, respectively. It is found that the distance between the pentacene grain boundaries decreases and an obvious layer structure can be formed in grains after annealing. According to the transport of carriers in the polycrystalline film, these changes of the pentacene film can improve the source--drain current and the mobility.