Solid state processing of organic semiconducting polymer blends

Organic electronics is an exciting scientific frontier that holds great promise for the manufacture of low-cost, flexible electronic devices. The advancement of these technologies relies on gaining a deeper understanding of important structure/ processing/property interrelationships in organic semiconductors. Addressing such fundamental questions enables the employment of well-defined schemes to efficiently improve device performances and optimise industrially relevant processing routes. Compression molding, a solid state process, is for example an excellent candidate for the manufacture of mechanically robust, freestanding organic semiconductor films with a high degree of molecular order and anisotropy. Regrettably, research into the use of such promising processing means are to date sorely lacking, limiting their applicability for future commercialisations. This thesis explores the solid state processing of the model semiconductor poly(3-hexylthiophene) (P3HT) and several blends with thermoplastic insulators. Studies herein address key areas in which solid state pressing has not yet been optimised and demonstrate versatile schemes that facilitate enhanced microstructure formation, molecular ordering and charge transport pathways in the freestanding films. Investigations further verify for the first time the highly anisotropic charge transport properties (as determined by time-of-flight photoconductivity measurements) that arise from solid state processing. Moreover, these flexible films, with well-defined semiconducting architectures, are envisaged as outstanding candidates for the regeneration of electroresponsive biological tissues and as regenerative platforms. The solid state processing protocols are therefore augmented with facile patterning techniques to replicate biologically relevant surface topographies, in the form of microgrooves, onto the film surfaces. Preliminary cell studies, using a cardiac-like cell line, indicate that the substrates support cell culture practices, and that the cells aligned on the groove surfaces. The results presented herein thereby demonstrate that solid state processing of neat organic semiconductors and their blends is a versatile and facile avenue to generate highly structured semiconducting architectures with potential bioelectronic applications.