Non-universal scaling of thermoelectric efficiency in 3D and 2D thermoelectric semiconductors

Abstract We performed the first-principles calculation on common thermoelectric semiconductors Bi 2 Te 3 , Se SiGe, and PbTe in bulk three-dimension (3D) two-dimension (2D). found that miniaturisation of materials does not generally increase figure merit ( ZT ) according to Hicks Dresselhaus (HD) theory. For example, values 2D (0.32) SiGe (0.04) are smaller than their 3D counterparts (0.49 0.09, respectively). Meanwhile, (0.57) (0.43) larger bulks (0.54 0.18, respectively), which agrees with HD The theory breakdown occurs because band gap flatness change upon dimensional reduction. flat bands give a electrical conductivity σ electronic thermal κ el materials, materials. In all cases, maximum proportionally saturate for above 10 k B T . obtain higher due corrugated narrow peaks DOS. violates flatter it exhibits, while possesses small Dirac-cone band.