Controlling the carrier and phonon transport behavior of SnSe via stoichiometric adjustment

Abstract

In this paper, we designed and fabricated SnSe1+x by vacuum melting with spark plasma sintering, and explored effect of stoichiometric change on energy band structure, bond anharmonicity and thermoelectric transport behavior under same process condition. Se overdose results in increase of electronical conductivity due to narrowing bandgap. Sn overdose causes obviously attenuated thermoelectric properties since the Fermi level moves up into the conduction band. The maximum powder factor value of 528 μWm−1K−2 for the SnSe1.01 sample at 773K results from energy gap reduction and steep density of states on valence band top. Non-stoichiometric defect causes enhancement of thermal conductivity due to evolution of bond characteristics between interlayers. The maximum ZT of the SnSe1.01 sample achieves 0.87 at 773K along “⊥” direction via stoichiometric adjustment.