Tuning functionality of printed conductive polymers using proximity ion beam lithograthy

Polymer semiconductors are used in low-cost electronics such as plastic solar cells, thin film transistors, and light-emitting diodes. Their performance in these devices is partly dictated by molecular ordering and nanoscale structure, where the latter is particularly difficult to control. We demonstrate a simple approach to control the structure and function of polymer semiconductors by patterning with proximity ion beam lithography (PIBL). The lithographic process generates intermolecular cross-links that render the polymer insoluble in organic solvents. The effects of PIBL exposure dose on optoelectronic properties and molecular ordering were investigated with measurements of ultraviolet-visible absorbance, hole mobility in the space-charge-limited regime, and crystallinity. We find evidence that extensive cross-linking will disrupt intermolecular ordering and introduce electronic trap states that reduce absorbance and mobility.