Optimization of electrical and thermal transport properties of layered Bi2O2Se via Nb doping

Layered oxygen-containing compound Bi 2 O 2 Se is a promising n-type thermoelectric material, favored by its considerably high Seebeck coefficient and low thermal conductivity. Significant preferred orientation along plane (110), identified in the hot-pressed sample, results in obvious anisotropy in the electrical and thermal transport properties. Nb substitution Bi in the insulating layer [Bi 2 O 2 ] 2+ can effectively increase the electron concentration (from 10 16 to 10 18  cm −3 ) by two orders of magnitude, while maintaining high mobility. Therefore, a larger power factor of 2.19 μW cm −1  K −2 has been obtained for Bi 1.94 Nb 0.06 O 2 Se at 823 K, which enlarges by three times in comparison with pristine Bi 2 O 2 Se (0.673 μW cm −1  K −2 ). Combined with the inherently low thermal conductivity, the ZT values of Bi 1.94 Nb 0.06 O 2 Se reach 0.195 at 823 K, corresponding to 325% enhancement. This study shows that the substitution of Nb for Bi is a promising way to optimize the thermoelectric properties of Bi 2 O 2 Se-based thermoelectric materials.