Thermoelectric technology has been widely used for key areas, including waste-heat recovery and solid-state cooling. We discovered tin selenide (SnSe) crystals with potential power generation and Peltier cooling performance. The extensive off-stoichiometric defects have a larger impact on the transport properties of SnSe, which motivated us to develop a lattice plainification strategy for defects engineering. We demonstrated that Cu can fill Sn vacancies to weaken defects scattering and boost carrier mobility, facilitating a power factor exceeding ~100 microwatts per centimeter per square kelvin and a dimensionless figure of merit ( ZT ) of ~1.5 at 300 kelvin, with an average ZT of ~2.2 at 300 to 773 kelvin. We further realized a single-leg efficiency of ~12.2% under a temperature difference (Δ T ) of ~300 kelvin and a seven-pair Peltier cooling Δ T max of ~61.2 kelvin at ambient temperature. Our observations are important for practical applications of SnSe crystals in power generation as well as electronic cooling.

We present a theoretical study of the tunneling magnetoresistance (TMR) and spin-polarized transport in Fe3Si/MgO/Fe3Si(001) magnetic tunnel junction (MTJ). It is found that the spin-polarized conductance and bias-dependent TMR ratios are rather sensitive to the structure of Fe3Si electrode. From the symmetry analysis of the band structures, we found that there is no spin-polarized Δ1 symmetry bands crossing the Fermi level for the cubic Fe3Si. In contrast, the tetragonal Fe3Si driven by in-plane strain reveals half-metal nature in terms of Δ1 state. The giant TMR ratios are predicted for both MTJs with cubic and tetragonal Fe3Si electrodes under zero bias. However, the giant TMR ratio resulting from interface resonant transmission for the former decreases rapidly with the bias. For the latter, the giant TMR ratio can maintain up to larger bias due to coherent transmission through the majority-spin Δ1 channel.

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