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

The charge carrier mobility in α,ω-dihexylquaterthiophene has been determined as a function of temperature using the Pulse-Radiolysis Time-Resolved Microwave Conductivity (PR-TRMC) and Thin Film Transistor (TFT) techniques. At room temperature a minimum value of 0.015 cm2/Vs was obtained with 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 °C and drops to less than 10−4 cm2/Vs above 180°C. These temperatures correspond to two reversible phase transitions discernable in DSC scans. With TFT experiments only the first phase transition could be studied, showing a decrease in mobility very similar to that observed in the PR-TRMC study.