Efficient enhancement of thermoelectric performance of CdTe via dilute hole doping together with heavy isoelectronic doping

Thermoelectric performances of p type and isoelectronically doped CdTe are investigated using first principles method and Boltzmman transport theory. For the supercell Cd32Te32, when one N atom is doped into it, the maximal S and ZeT are only 156 μV/K and 0.76, respectively, but the ZeT values are much smaller at 300-700 K for P, As and Sb dopings. However, if eight Sr atoms are further doped into Cd32Te31M (M= pnicogen) to substitute Cd atoms, all the four maximal S values exceed 242 μV/K, and the ZeT reaches 1.5 at 1000 K for N doping, but for P, As and Sb dopings the values do not exceed 1.0. The large S arises from the steep but low DOS at EF. The enhancement in ZeT results from the S dominating over σ/κe. The number and distribution of Sr atoms have an impact on the ZeT values. Adding one or two O atoms further can hoist the ZeT at 700 K and 800 K significantly. When one Cl atom and one Na atom are doped into Cd24Sr8Te31N, the ZeT reaches 1.7 at 1000 K. The results show that hole doping combined with heavily isoelectronic doping is efficient on improving the electronic figures of merit of semiconductors if appropriate doped elements are chosen. The way of doping assumed here should be applicable for other semiconductor systems.