We compute the thermoelectric power factor of a nanoporous matrix material. Although the porous material is a connected, extended system, where perfect confinement cannot take place, we show that "quasi-confinement" can occur, thus increasing the matrix's optimized power factor above bulk values. For parabolic band materials, we obtain a set of universal curves that express the power factor enhancement with respect to bulk values in terms of a single quantity relating the temperature, pore separation, and bulk effective mass. We show how results deviate from these universal curves when the bulk material's bands are not parabolic. Reduction of the lattice thermal conductivity is also addressed. The use of a good thermoelectric material instead of a dielectric as the matrix for thermoelectric nanocomposites might thus enhance the overall nanocomposite's power factor, and it could be advantageous for power generation applications in which the goal is to maximize the generated power.
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