Oligothiophenes in organic thin film transistors - Morphology, stability and temperature operation

We have investigated a series of oligothiophenes in organic thin film transistors (TFTs), with special emphasis on their thin film morphology related to device performance and application requirements. The transistor performance was studied for devices fabricated at different substrate temperatures during semiconductor deposition (ranging from room temperature to 120 degrees C). A significant dependence of thin film morphology on the substrate temperature was observed, whereas the charge carrier mobility in devices occurs almost unaffected. We have tested the long-term stability of 78 transistor devices (shelf-life in ambient conditions) over a period up to 100 days. Only a small degradation in mobility by less than one order of magnitude was observed. Investigations at elevated temperatures during TFT operation (room temperature to 105 degrees C) show that devices with alpha,alpha '-hexylsexithiophene (Hex-6T-Hex) degrade in their charge carrier mobility by a factor of 8, but completely recover to their initial value of 0.7 cm(2)/Vs after a short period of storage at room temperature in ambient conditions. (C) 2008 Elsevier B.V. All rights reserved.