Nano-scale dislocations induced by self-vacancy engineering yielding extraordinary n-type thermoelectric Pb_0.96-yIn_ySe

Nanostructuring has successfully enhanced thermoelectric performance for wide solid-state materials via embedding nano-scale particles, precipitates, or dislocations into the matrix to significantly lower the thermal conductivity. Herein, high-density dislocations are successfully introduced through engineering the off-stoichiometry ratio of cation atoms in Pb_1-xSe. As examined by electron microscopy characterizations and phonon transport modeling studies, the existence of dense nano-scale dislocations in conjunction with grain boundaries and point defects lead to the strong wide-frequency phonon scatterings. Consequently, lattice thermal conductivity is significantly decreased in Pb_1-xSe. Through doping In into the Pb_0.96Se with an ultralow lattice thermal conductivity, the carrier concentration is tuned to reach the optimal level, which is confirmed by our modeling investigations. The synergistically obtained high-density of dislocations and the optimized carrier concentration lead to an extraordinary figure-of-merit of 1.6 in n-type Pb_0.96-yIn_ySe. This study demonstrates a natural way to induce high-density nano-scale dislocations by self-vacancy engineering, which extends the strategy of nanostructuring to broader materials for developing high-performance thermoelectric candidates.