Design Rules for Dynamic-Template-Directed Crystallization of Conjugated Polymers
The multiscale morphology and device performance of printed semiconducting polymers are highly sensitive to the substrate/ink interfacial properties during solution coating. There is an urgent need of general design rules correlating substrate properties and conjugated polymer (CP) morphology, which do not yet exist. Dynamic surfaces are particularly promising for templating highly crystalline and highly aligned conjugated polymer thin films shown in recent works. Herein, we implement the dynamic-templating method using a series of liquid-infused nanoporous substrates as a tool to study the impact of template reconfigurability and chemistry on multiscale morphology of conjugated polymer thin films, using a high performing donor-acceptor polymer (DPP-BTz) as a model compound. By quantifying enthalpy of adsorption, we demonstrate that the strength of template-CP interactions directly measures the effectiveness of dynamic surfaces in promoting conjugated polymer crystallization and alignment. We further show that enthalpy of interactions increases by enhancing template dynamics and are sensitively modulated by template chemistry. Specifically, increasing template-CP interactions leads to larger domain size and higher degree of crystallinity in templated conjugated polymer thin films prepared by meniscus-guided solution coating. This observation validates our hypothesis that dynamic templates function by promoting nucleation of conjugated polymers. We also demonstrate that such dynamic-template-dependent morphology is independent of coating speed. Notably, the enhanced morphological properties modulate the charge carrier mobility in field-effect transistors (FETs) over an order of magnitude reaching hole mobility of 2.8 cm2V-1s-1. This work is a significant step towards establishing general guidelines on how substrate-ink interfacial properties influence morphology and performance of solution coated CP thin films.