Super Large Sn1- xSe Single Crystals with Excellent Thermoelectric Performance.

SnSe single crystals have drawn extensive attention for their ultralow thermal conductivity and outstanding thermoelectric performance. Here, we report super large Sn1- xSe single crystals with excellent thermoelectric properties, fabricated via an advanced horizontal Bridgman technique with great yield and high reproducibility. The obtained single crystals have a super large size of ∼70 × 50 × 15 mm with a considerable weight of 148 g, which leads to a record-high mass density of >6.1 g cm-3. Extensive chemical characterization demonstrates that ∼0.3% Sn vacancies are present, which results in a large concentration of holes, ∼1.2 × 1019 cm-3, and an enhanced power factor of ∼6.1 μW cm-1 K-2 at 793 K. Simultaneously, the Sn-vacancy-induced lattice distortions result in a low thermal conductivity of ∼0.39 W m-1 K-1 at 793 K, leading to a competitive ZT of ∼1.24. This work demonstrates that large-size off-stoichiometric SnSe single crystals hold promise to achieve high thermoelectric performance.