Super Large SnSe 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 SnSe 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. Extensive chemical characterization demonstrates that ∼0.3% Sn vacancies are present, which results in a large concentration of holes, ∼1.2 × 10 cm, and an enhanced power factor of ∼6.1 μW cm K at 793 K. Simultaneously, the Sn-vacancy-induced lattice distortions result in a low thermal conductivity of ∼0.39 W m K 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.