Air-stability analysis and improvement of poly(3-hexylthiophene) field-effect transistors

The influence of air, dry oxygen and humidity on the performance of a top-contact polymer field-effect transistor using poly(3-hexylthiophene) (P3HT) as an active layer is investigated. It is demonstrated that high relative humidity (92%) causes the device to degrade rapidly, while the influence of dry oxygen on the device is relatively small, indicating that the harmful influences are mainly the result of atmospheric water due to the enhancement of carrier conduction in the vicinity of the active-layer surface caused by the absorption of water molecules on the surface, rather than the p-type doping effect of O-2. A photoresist or paraffin layer is utilized as a passivation layer on top of the P3HT film, and the effects of the passivation layer on the performance and stability of the device are investigated. Results indicate that the passivation layer can effectively improve the stability of the device exposed to air, and enhance its field-effect mobility.