Crystals and films of conjugated molecules transport charge and can be used as functional semiconductors in thin film transistors, photovoltaic devices, and light-emitting diodes. My research program focuses on understanding connections between structure and electrical transport behavior in organic semiconductors. We are particularly interested in the dependence of electron and hole mobility (the velocity per unit electric field) on molecular structure, crystal packing, intermolecular bonding, and defects in organic crystals and films. A theme of our experimental investigations is the development of methods for measuring transport behavior on length scales spanning nanometers to microns, so that we can accurately characterize the effects of specific structural features on transport.