Characterization of solution-processed pentacene thin film transistors

The electrical and chemical stability of solution-processed pentacene thin film transistors (TFTs) was investigated using analytical models reported by Horowitz et al. in comparison with vacuum-deposited TFTs. The estimated total trap density of the solution-processed film was one to two order(s) of magnitude lower than that of the vacuum-deposited film. The low trap density of the solution-processed film is due to large crystalline domains, which include only a few structural defects, in contrast to the vacuum-deposited film. The solution-processed film is also superior to the vacuum-deposited film in electrical stability during long-term storage in air. That is, a considerable shift of the transistor characteristics in the subthreshold region including a threshold voltage was observed, especially in the case of the vacuum-deposited TFT. The change in the electrical properties is attributed to the increase of oxidation-induced chemical impurities, which were confirmed by surface mass spectroscopy. (c) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim