Enhanced Thermoelectric Performance of Ultrathin Bi 2 Se 3 Nanosheets through Thickness Control

Large‐scale Bi 2 Se 3 nanosheets with controllable thickness have been synthesized by a microwave‐assisted solvothermal method. Through detailed structural characterizations, high‐quality Bi 2 Se 3 nanosheets with average thickness of 1, 4, 7, and 13 nm have been fabricated. Their thermoelectric performance has been detailed investigated by experiments and fundamental nonparabolic Kane models. A significantly reduced thermal conductivity (only 0.41 W m ‐1 K ‐1 ), and enhanced powder factor (4.71 × 10 ‐4 W m ‐1 K ‐2 with a Seebeck coefficient of –155.32 μV K ‐1 and an electrical conductivity of 1.96 × 10 4 S m ‐1 ) are observed in the pellet composed of single‐layered Bi 2 Se 3 nanosheets. Such an enhanced thermoelectric performance is ascribed to the broadened bandgap and optimized Fermi level in ultrathin Bi 2 Se 3 nanosheets.