(284f) Understanding Film-to-Wire Transition of Conjugated Polymers Driven By Meniscus Instability

Meniscus-guided solution coating has been widely adopted as a highly effective fabrication method for high-throughput, low-cost and large-area coating of functional materials in various systems. During solution coating and printing of semiconducting polymers, meniscus instability often arises and results in complex morphology of the deposit that presents both challenges and opportunities for controlling molecular assembly and electronic properties of semiconducting polymers. Therefore, understanding meniscus instability during solution coating and its impact on deposited conjugated polymers is not only of fundamental importance, but also critical for large scale manufacturing of high performance printed electronic devices with controlled morphology.

In this work, we observed coating speed dependent film-to-nanowire morphology transition driven by stick-and-slip meniscus instability across multiple high-performance donor-acceptor conjugated polymer systems. Interestingly, the nanowires exhibit different molecular stacking and higher charge carrier mobility compared to thin films deposited at the same condition. We hypothesize that the film-to-wire morphology transition is determined by minimization of the meniscus surface free energy during the stick-and-slip meniscus motion. We validated the hypothesis by constructing a quantitative surface free energy model and successfully showed the peak of meniscus surface free energy occurring at the transition coating speed. This work is a significant first step towards quantitative understanding of meniscus-instability-driven morphology transition during solution coating, which represents a promising approach for lithography-free patterning. Our study has broad implications beyond printed electronics, given the critical importance of controlling meniscus instability and deposit morphology in a wide range of scientific disciplines and technology sectors.