Film Morphology and Thin Film Transistor Performance of Solution-Processed Oligothiophenes

The relationship between film morphology and thin film transistor (TFT) performance was investigated for two symmetrical (alpha),(omega)-substituted sexithiophene derivatives containing thermally removable solubilizing groups. Solution deposition methods such as spin-coating, dip-casting, and inkjet-printing were optimized for solvent and annealing temperatures, and several substrate surface treatments were explored. The resulting thin films were characterized with AFM and the observed semiconductor performance was found to correlate with the morphology of the films, with the most crystalline films exhibiting the highest performance. Devices showed overall mobilities as high as 0.07 cm^2/V s with on/off ratios > 10^8, which are among the highest reported values for oligothiophenes solution cast at room temperature.