Enhanced Stability of Organic Field-Effect Transistors with Blend Pentacene/Anthradithiophene Films

By taking advantage of the similarity between pentacene (PEN) and anthradithiophene (ADT) in molecular dimension and charge transport property, we have produced organic field-effect transistors (OFETs) with active layers consisting of well-blended PEN/ADT films. The blend-films were characterized by atomic force microscopy, X-ray diffraction, and soft X-ray spectroscopies. It is found that the blend-films containing no more than 10% of ADT exhibit a single-phase structure, large crystallinity, and improved oxidation resistance, as compared to PEN. The best performance achieved with 90% PEN-OFET gives a mobility of 0.37 cm² V^–1 s^–1 and an on/off current ratio of 10⁷. More importantly, this device provides a 3-fold improvement in operational stability as well as extended environmental stability. After the repetitive scanning between on and off states of OFET in ambient 940 times, the mobility decreases only to 0.33 cm² V^–1 s^–1. In comparison, the mobility of PEN-OFET decreases from 0.46 to 0.22 cm² V^–1 s^–1. After 3-month storage in ambient, the mobility of the optimal device decreases to 0.1 cm² V^–1 s^–1, whereas PEN-OFET almost loses its mobility