Thermoelectric (TE) devices already found a wide range of commercial, military and aerospace applications. However, at present commercially available TE devices typically offer limited heat to electricity conversion efficiencies, well below the fundamental thermodynamic limit, calling for the development of higher efficiency materials. The team of MicroXact Inc., Virginia Tech and Sundew Technologies Inc. is proposing to develop a revolutionary ultrahigh efficiency thermoelectric material fabricated on completely new fabrication principles. The material comprises the three-dimensional "wells" of Bi2Te3/Bb2Te3 Quantum Well Superlattices fabricated by a conformal coating of macroporous silicon (MPSi) pore walls. Such a material will provide ZT >2 at macroscopic thicknesses of the material, permitting 15% or more conversion efficiencies. In Phase I of the project the thorough model of the proposed TE material was developed, the achievable efficiency and ZT of the material were confirmed through numerical modeling, and conformal coating of pore walls with Sb2Te3 was experimentally demonstrated, validating the proposed concept. In Phase II the team will fabricate the proposed material and device, and will demonstrate ZT>2 and conversion efficiencies exceeding 15%. After the Phase II MicroXact will commercialize the technology.