Organic thin film transistor (OTFT) gas sensors fabricated with an array of different active materials are monitored for shifts in performance characteristics during continuous operation over many days in both inert and ambient environments. We analyze the different patterns of degradation behavior observed in different materials and discuss approaches to decoupling a device's sensor response from its stress response.

Here we report on OTFTs made from a novel thermoresponsive thiophene based oligomer. The functionalized oligomer is soluble in common solvents, but loses its solubility upon thermolysis. Devices with channel lengths from 5 to 40 νm were fabricated from solution then subjected to thermolysis at temperatures ranging from 150-250°C. The initially amorphous materials reorganize into highly crystalline films upon thermolysis. Crystallinity was characterized by x-ray diffractometry and atomic force imaging. AFM studies depicted the nucleation of molecular terraces, where the formation and overall height of terraces was observed to be dependent upon the thermolysis temperature and solvent choice. These factors correlated to overall performance. For both dip-cast and spin-cast samples, devices were fabricated at a process temperature of 180°C with mobilities of 0.07 cm2/Vs and on/off ratios > 105. The deves were relatively stable in both air and common solvents, with their mobility degrading only by ∼25% upon immersion in the original casting solvents. The solubility characteristics and process temperatures for these devices may be particularly suitable for solution processing on flexible substrates.