Tactfully decoupling interdependent electrical parameters via interstitial defects for SnTe thermoelectrics

Abstract

SnTe is a promising alternative of the moderate-temperature thermoelectric material PbTe owing to its earth-abundant and nontoxic nature. However, its several shortcomings, such as small Seebeck coefficient thus poor power factor and upper lattice thermal conductivity, which have restricted overall thermoelectric performance of SnTe. In this scenario, an effective approach to decouple electrical parameters of electrical conductivity and Seebeck coefficient typified by introducing Vanadium (V) interstitial defects, realizing an ultrahigh power factor and a reduction in lattice thermal conductivity has been presented in SnTe system. Concretely, the V-interstitial defects caused by alloying V with SnTe enable lower formation energy of intrinsic Sn vacancies and holistic weak chemical bonding surrounded by Sn atom, thereby improving carrier density and the overall electrical conductivity. Meanwhile, the high-temperature Seebeck coefficient was significantly enhanced due to the increased valence band convergence and in-situ self-doping effect induced by V-interstitials. Moreover, beneficial from the hierarchical crystal defects and microstructure, the independent lattice thermal conductivity had been greatly reduced to its amorphous limit of ~0.4 Wm−1K−1. In virtue of these multiple functions of V-interstitials, a record-high power factor of ~37.4 μWcm−1K−2 by single element alloying and an enhanced zT value of ~1.3 at 873 K, combined with a calculated engineering output power density ~263 Wcm−2, were achieved in the Sn0.98V0.02Te sample. Conclusively, this work provides an ingenious way to further maximize its electrical performance despite the already-high electrical conductivity of SnTe, impelling the potential application of SnTe for high output power density, and this may also apply to other highly conductive thermoelectric systems.