Evaluating the Impact of Chemical Structure on the Interactions and Optoelectronic Performance of Conjugated Small Molecules

Conjugated organic molecules have significant untapped potential in the field of organic electronics. The theoretical capabilities of many organic materials are excellent, but the real world results often fall short. Some areas of study, like organic field effect transistors (OFETs) and organic photovoltaics (OPVs), are in a state of regular advancement, yet many unanswered questions and unknown variables remain regarding the inherent structure-property relationship of organic components of these systems. We set out to study this crucial relation in our own way, targeting and synthesizing compounds we believe can give us some insight into what role the chemical structure plays in device performance. We hope that the lessons learned here can be used to create even better next generation materials and elucidate important design rules or which structural features to avoid. In Chapter 1, we outline the current state of the field and the reasoning that led us to pursue the work described in the subsequent Chapters. The second Chapter of this dissertation details the synthesis of several new anthradithiophene (ADT) derivatives and evaluates the effect of heteroatom functional groups on the opto-electric properties, crystal packing, and OFET device performance they exhibit. One new ADT substituent greatly increased the photo-oxidative stability of the ADT core compared to other known stabilizing groups, offering a new means of solubilizing and stabilizing larger acene compounds. Two previously unreported linear acene crystal packing motifs were also discovered for two of the new ADT derivatives we synthesized. Thin film formation of the ADT derivatives showed some interesting differences between functional groups, and at least one derivative showed strong potential for future optimization and study in OFETs. The third Chapter deals with the synthesis, characterization, and OPV results of a series of new A-D-A molecules functionalized with tricyano-furan acceptor units. We compared these new A-D-A compounds with similar molecules functionalized by the current top acceptor unit IC. The fourth Chapter concludes the ADT and A-D-A projects while discussing what we have learned from the results. Future research directions are outlined that could further our understanding of the structure-property relationship that is key to OFET and OPV performance. Additionally, we describe our early work into the synthesis of a novel modified TCF analogue that hopefully will fix the flaws we observed in the TCF acceptors.Doctor of Philosoph