Charge carrier mobilities in mesomorphic alpha,omega-dihexylquaterthiophene: A comparative microwave conductivity and thin film transistor study

The charge carrier mobility in alpha,omega-dihexylquaterthiophene has been determined as a function of temperature using the Pulse-Radiolysis Time-Res olved Microwave Conductivity (PR-TRMC) and Thin Film Transistor (TFT) techn iques. At room temperature a minimum value of 0.015 cm(2)/Vs was obtained w ith PR-TRMC for the amorphous powder, close to the mobility obtained in TFT experiments on a well-ordered film. The PR-TRMC mobility decreases by 30% at 81 degrees C and drops to less than 10(-4) cm(2)/Vs above 180 degrees C. These temperatures correspond to two reversible phase transitions discerna ble in DSC scans, with TFT experiments only the first phase transition coul d be studied, showing a decrease in mobility very similar to that observed in the PR-TRMC study.