Thermoelectric generators convert the flow of heat directly into electrical energy. Such devices can improve our energy efficiency; however, advanced materials with improved conversion efficiency are required for widespread implementation. Improving thermoelectric efficiency requires reconciling competing electronic and thermal transport properties – a material must have both a large carrier effective mass and mobility and low lattice thermal conductivity. This talk will focus on materials which achieve these conflicting properties through modifications of the electron and phonon band structures. Such tailored control of transport properties will be vital to realize the next generation of energy materials.