Conjugated Polymer Alignment: Synergisms Derived from Microfluidic Shear Design and UV Irradiation.

Solution shearing has attracted great interest for the fabrication of robust and reliable, high performance organic electronic devices, owing to applicability of the method to large area and continuous fabrication, as well as its propensity to enhance semiconductor charge transport characteristics. To date, effects of the design of the blade shear features (especially the microfluidic shear design) and the prospect of synergistically combining the shear approach with an alternate process strategy have not been investigated. Here, a generic thin film fabrication concept that enhanced conjugated polymer intermolecular alignment and aggregation, improved orientation (both nanoscale and long-range), and narrowed the π-π stacking distance is demonstrated for the first time.

Microfluidic Crystal Engineering of π-Conjugated Polymers.

Very few studies have reported oriented crystallization of conjugated polymers directly in solution. Here, solution crystallization of conjugated polymers in a microfluidic system is found to produce tightly π-stacked fibers with commensurate improved charge transport characteristics. For poly(3-hexylthiophene) (P3HT) films, processing under flow caused exciton bandwidth to decrease from 140 to 25 meV, π-π stacking distance to decrease from 3.

Photoinduced Anisotropic Assembly of Conjugated Polymers in Insulating Polymer Blends.

Low-dose UV irradiation of poly(3-hexylthiophene) (P3HT)-insulating polymer (polystyrene (PS) or polyisobutylene (PIB)) blend solutions led to the formation of highly ordered P3HT nanofibrillar structures in solidified thin films. The P3HT nanofibers were effectively interconnected through P3HT islands phase-separated from insulating polymer regions in blend films comprising a relatively low fraction of P3HT. Films prepared with a P3HT content as low as 5 wt % exhibited excellent macroscopic charge transport characteristics.

Ultrasound-induced ordering in poly(3-hexylthiophene): role of molecular and process parameters on morphology and charge transport.

Facile methods for controlling the microstructure of polymeric semiconductors are critical to the success of large area flexible electronics. Here we explore ultrasonic irradiation of solutions of poly(3-hexylthiophene) (P3HT) as a simple route to creating ordered molecular aggregates that result in a one to two order of magnitude improvement in field effect mobility. A detailed investigation of the ultrasound induced phenomenon, including the role of solvent, polymer regioregularity (RR) and film deposition method, is conducted.