Adv. Functional Mater. http://doi.org/f272xv (2015)

The morphology of the conducting channel strongly affects the performance of organic transistors based on small molecules. Recently, it was observed that pentacene thin films evaporated on holey insulators show a porous morphology that decreases the formation of grain boundaries in the film and leads to improved charge transport. Deyang Ji and colleagues now report that an analogous strategy is effective in reducing the contact resistance and enhancing charge carrier injection from the contacts of the transistor to the conducting channel. Gold pads having holes with diameters ranging from 300 to 500 nm were realized by nanosphere lithography on a silicon substrate, and pentacene molecules were vacuum-deposited on top of this device after plasma treatment. The holes induce a nanoporous texture in the organic film grown on the gold contacts and increase the size of the pentacene grains forming the conducting channel. Such improved morphology leads to an enhancement of the charge carrier mobility and output current of the transistors.