Bottom-contact poly(3,3‴-didodecylquaterthiophene) thin-film transistors with reduced contact resistance

A dramatic, ∼20-fold, reduction in the contact resistance of the bottom-contact poly(3,3‴-didodecylquaterthiophene) (PQT-12) thin-film transistors was achieved through a simple treatment of gold (Au) source and drain electrodes. The Au electrode treatment involved simply immersing the Au electrodes into Piranha solution prior to the deposition of the organic semiconductor. This treatment led to significant improvement of device performance. Channel length scaling analysis indicates that the contact resistance is reduced by about one order of magnitude, resulting in enhancement of estimated field-effect mobility by about a factor of five. Transport characteristic analysis suggests that the improved efficiency of charge carrier injection is probably due to increased dopant density of PQT-12 at the electrode/PQT-12 interface.