Solid-state processing of organic semiconductors.

Solid-state processing of conjugated small molecular, oligomeric and polymeric compounds was conducted. Solid, powdered material was placed in a hot press, followed by compression molding well below the melting temperatures of the species, typically at pressures of approximately 10 30 kN cm-2. In order to investigate whether or not solid-state processing deteriorated electronic properties of the semiconductors, time-of-flight (TOF) photoconductivity experiments were conducted, which allow determination of bulk charge transport across thin film architectures. A typical small-molecular compound (6T) and two polymeric species P3HT and the liquid-crystalline PBTTT-C16, were selected. It was demonstrated that bulk carrier mobilities derived from TOF studies did not deteriorate, but in some cases actually could be significantly enhanced when compared to conventionally processed structures. Interfacial charge transport both for electrons and holes was not affected, despite processing the organic semiconductors in light and air

Solid-state low-temperature extrusion of P3HT ribbons

Ribbons of poly(3-hexylthiophene) (P3HT) 0.15 and 0.30 mm thickness were extruded at the temperatures of 200 and 250 C, i.e., below and above the melting temperature of P3HT (~240 C), using a small homemade extrusion device. The ribbons produced by this method are continuous and freestanding. WAXS results show that all the extruded samples are more crystalline than the original powder, and the different processing conditions cause different variations in the crystal unit cell dimensions of P3HT. In terms of the degree of orientation, the ribbons extruded in the solid state (TTm), which is fully isotropic.This work was supported by FCT (Fundação para a Ciência e Tecnologia) through the program PEst-C/CTM/LA0025/2013 (Strategic Project—LA 25—2013–2014) and by the European Regional Development Fund (FEDER) through the program COMPETE (Project PTDC/CTM-POL/120843/2010). DN and DGB gratefully acknowledge partial support of this work from the U.S. Department of Energy, Division of Basic Energy Sciences under contract No. DE-FG02-10ER4779