Orthogonal processing: A novel photolithographic patterning method for organic electronics

Organic electronics is an extensively studied subject opening new horizons in electronics technology. It has attracted great attention as a technology to enable flexible electronic devices through solution processing of organic and polymeric materials. However, patterning of organic materials to construct device components still remains one of the major hurdles to be overcome due to problems with chemical processing. Fundamentally this challenge originates from the limited number of options regarding orthogonal solvents. Recently, we have identified supercritical carbon dioxide (scCO₂) and segregated hydrofluoroethers (HFEs) as universal, non-damaging solvents for most non-fluorinated polymeric materials. These unconventional solvents expand processing options from the two-dimensional plane to three-dimensional space by drawing another orthogonal axis. Taking advantage of those noble solvents and fluorinated photoresists, we were able to make patterns of functional organic materials photolithographically. Furthermore, our orthogonal processing method has been applied to the fabrication of a patterned polymer light-emitting device in scCO₂ and an organic thin-film transisotor in HFEs.