Contrasting Thermoelectric Transport Properties of n-Type PbS Induced by Adding Ni and Zn

Introducing small metallic atoms is an effective approach to enhance thermoelectric performance. In this research, we investigate the impacts of Ni and Zn on the thermoelectric performance of n-type PbS. We find that adding Ni is superior to that of Zn. Both experimental and theoretical results show that the extra Ni could bring a new impurity level among the Fermi energy, thus the electrons can be easily excited from defect states, leading to enhanced carrier mobility. Above all, adding Ni can boost the thermoelectric performance of n-type PbS dramatically. A peak ZT value at 823 K and a ZTave value of Pb0.995In0.005S + 5% Ni were achieved as ∼1.0 and ∼0.66, respectively.