Photopolymerizing carbazole-based monomers in dilute media: prototyping organic wires with nanoscale thickness control

Abstract

Direct laser writing of conductive materials is a highly desirable route for quickly prototyping organic circuits in a flexible manner. In this paper, we extend the scope of such methodologies in the field of conductive polymers by designing a strategy for preparing local poly carbazole layers onto inert surfaces. We formulate a monomer activation methodology based on rational photoredox sensitizer selection. After analyzing the interaction between the sensitizer and carbazole monomers, we demonstrate that local formation of conductive surface layers can be achieved. With the help of the custom optical nanometrology setup, local polymerization kinetics are measured and used to optimize the reaction conditions, achieving diffraction limited lateral resolution and precise geometry control, preparing layers with thickness as thin as 10 nm and spanning several orders of magnitude. Counterintuitively, we show that dilute solutions are suitable for high resolution surface modification, and that at the microscale, diffusive resolution loss can be safely neglected. The potential of the approach for prototyping organic circuits is demonstrated by preparing a variety of functional (conductive) patterns on inert glass surfaces, measuring their conductivity and optical properties.