Poly(3-hexylthiophene) (P3HT) is one of a class of semiconducting polymers heavily investigated for flexible electronic devices such as transistors, photovoltaics, sensors and light emitting diodes. Processing of these flexible active layers promises to be cheaper and more versatile, because they can be coated onto substrates at low temperature from a solution or colloidal suspension. Aqueous processing using field-assisted deposition is investigated in this work for more precise assembly into structures on an electrode-patterned substrate. Our previous research found that when a water droplet with suspended P3HT colloidal particles evaporates on solid substrate, a coffee-ring will form at contact line due to capillary flow. This coffee-ring effect is undesirable because a uniform coating is needed for good electronic performance. Many proposed methods to eliminate the coffee-ring effect require high-precision, multi-step control or the use of toxic organic solvent. In this work, dielectrophoresis (DEP) was used to assemble particles into chains, monolayers and multilayers. Under the A/C electronic field, particles will assemble into a colloidal crystal, then settle to the surface of the substrate, which provides higher resistance to capillary flow. This structure prevents the particles from flowing outward to the droplet edge thus creating more uniform coating. We elucidate the influence of particle properties, drying kinetics, DEP field parameters and suspension concentration on the uniform distribution of particles in the final coating.<br/>

Suppression of coffee-ring effect by employing dielectrophoresis force

256th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.