Potential barrier/well engineering for improving the power factor in nanostructured thermoelectric materials

Energy filtering is one of the most successful ways to improve the Seebeck coefficient in nanostructured materials and superlattices. Despite the fact that nanostructuring emerges as the most promising method to reduce thermal conductivity and improve ZT, to-date, energy filtering has not been widely utilized because it did not achieve sufficient improvements in the thermoelectric power factor. In this work, we present a theoretical analysis of a novel concept for efficient design of the potential well/barrier region such that very large power factor improvements are achieved. The concept proposed combines aspects of: i) energy filtering from potential barriers with thermionically emitted carriers, ii) highly degenerate doping conditions but with non-uniform distribution of dopants, and iii) reduced energy relaxation of carriers after they passed the barriers and propagate into the wells. We employ simple analytical models, but verify the main design ‘ingredients’ with more advanced Non-Equilibrium Green’s Function (NEGF) quantum transport simulations and semiclassical Monte Carlo simulations.