Figure 6: The ZTs against ∆u.

The maximum ZTs from different chalcopyrites, such as, CuGa1−xInxTe238, annealed CuGaTe219 and Cu1−xIn1−xZn2xTe240 are presented for comparison. These chalcopyrite compounds all show that they do not have the highest ZTs at ∆u = 0, but at a certain ∆u value. An insert is close-up view of present relation between ZTs and ∆u. The ZT value reaches the highest at ∆u = 0.15 × 10−3, rather than at ∆u = 0.