Figure 1: Pathway and progress for high ZT in TE materials.

Conventional bulk materials have values from 0.01 to around 1, by using nanostructures, values between 0.1 to 2 have been reported for SnSe (ZT300 K 0.12; ref. 4), quantum nanodot AgPbmSbTe2+m alloys (ZT800 K 2.2; ref. 5), Bi2Te3/Sb2Te3 superlattices (ZT300 K 2.4; ref. 8) and Si nanowires (ZT200 K 1; ref. 15). We present negatively correlated materials, which offer another method for increase of ZT. The solid blue arrow indicates previous progress, while the dotted red arrow is our proposed approach for further increased ZT.