Abstract: Our group’s research focuses on directional interactions in ordered assemblies of organic semiconductors. Using tools of single-molecule spectroscopy, our approach is based on isolated crystalline nanowires where the nanowire itself plays a material role analogous to a single molecule, and optical polarization (in either absorption or emission) can be referenced to specific crystallographic directions. Of particular interest are timescales for mixing transverse and longitudinal polarizations which encode information on the (directional) interaction of different intermolecular coupling modes in the assembly. In this talk, I’ll summarize some recent work on isolated crystalline nanowires of an interesting small-molecule semiconductor called 7,8,15,16-tetraazaterrylene (TAT, for short) which display several unusual and exciting properties with applications to organic opto-electronics.