Rapid and non-destructive optical patterning of conjugated polymers for device applications*

A significant obstacle for the industrial development of organic electronic devices is the lack of a patterning technology having the disruptive power that photolithography exerted in traditional microelectronics. Here we present a new scalable patterning technology for organic semiconductors that takes advantage of the existing photolithography infrastructure and is compatible with digital direct-write patterning and sequential roll-to-roll (R2R) solution coating. The Moule group works on a series of solubility control techniques including the use of marginal solvents and polymer doping, that reduce the solubility of polymers at room temperature, but allow patterning at elevated temperatures. Using these techniques, we are able to vertically stack and laterally pattern mutually soluble polymer layers, which are vital processing steps needed to expand the use of organic semiconductors in device applications. Optimization of these techniques has yielded diffraction limited film patterning with regular features of 200-300 nm with only solution processing steps and direct write laser patterning. We have also recently shown that vertically patterned layers are stable, even with solvent exposure times of hours. This presentation will cover the fundamentals of optical patterning of organic semiconductors and delve into details of how to create doped microdomains, dopant diffusion, and the relationship between polymer crystallinity, dopant diffusion rate, and pattern fidelity.