The behavior and application of organic semiconductor materials depend strongly on their molecular structure, and molecular interactions. Several studies of intermolecular interactions in functionalized polyacene materials are presented. The degree and onset of aggregation of a functionalized anthradithiophene derivative was studied as a function of concentration in two different host matrices. The molecular environment was found to influence the degree and onset, but not the nature of aggregate formed. The effect of aggregation on photoconductivity was also studied. In a blend of two different anthradithiophene derivatives, the intermolecular separation was found to affect the nature of the interaction, transitioning from energy transfer at large intermolecular distances to the formation of an emissive excited state complex at smaller intermolecular distances. This complex was shown to have effects on both photoluminescence and photoconductivity. Finally, a single molecule fluorescence microscopy system was built and characterized. Software was written to process data produced from the system and several classes of functionalized polyacenes were studied at the single molecule level. In particular, the photophysics and molecular orientation of various derivatives were quantified. A new solution-processable, photoconductive, polycrystalline host material was found to be suitable for single molecule imaging, and the molecular orientations of individual molecules were found to depend on both their molecular structures and their local nano-environment.