Enhancement of Thermoelectric Performance of n-Type PbSe by Cr Doping with Optimized Carrier Concentration

Ti, V, Cr, Nb, and Mo are found to be effective at increasing the Seebeck coefficient and power factor of n-type PbSe at temperatures below 600 K. It is found that the higher Seebeck coefficients and power factors are due to higher Hall mobility ≈1000 cm2 V-1s-1 at lower carrier concentration. A larger average ZT value (relevant for applications) can be obtained by an optimization of carrier concentration to ≈1018–1019 cm-3. Even though the highest room temperature power factor ≈3.3 × 10-3 W m-1 K-2 is found in 1 at% Mo-doped PbSe, the highest ZT is achieved in Cr-doped PbSe. Combined with the lower thermal conductivity, ZT is improved to ≈0.4 at room temperature and peak ZTs of ≈1.0 are observed at ≈573 K for Pb0.9925Cr0.0075Se and ≈673 K for Pb0.995Cr0.005Se. The calculated device efficiency of Pb0.995Cr0.005Se is as high as ≈12.5% with cold side 300 K and hot side 873 K, higher than those of all the n-type PbSe materials reported in the literature.