Enhanced thermoelectric performance of n ‐type Bi 2 O 2 Se by Cl‐doping at Se site

The n ‐type polycrystalline Bi 2 O 2 Se 1− x Cl x (0≤ x ≤0.04) samples were fabricated through solid‐state reaction followed by spark plasma sintering. The carrier concentration was markedly increased to 1.38×10 20 cm −3 by 1.5% Cl doping. The maximum electrical conductivity is 213.0 S/cm for x =0.015 at 823 K, which is much larger than 6.2 S/cm for pristine Bi 2 O 2 Se. Furthermore, the considerable enhancement of the electrical conductivity outweighs the moderate reduction of the Seebeck coefficient by Cl doping, thus contributing to a high power factor of 244.40 μ·WK −2 ·m −1 at 823 K. Coupled with the intrinsically suppressed thermal conductivity originating from the low velocity of sound and Young's modulus, a ZT of 0.23 at 823 K for Bi 2 O 2 Se 0.985 Cl 0.015 was achieved, which is almost threefold the value attained in pristine Bi 2 O 2 Se. It reveals that Se‐site doping can be an effective strategy for improving the thermoelectric performance of the layered Bi 2 O 2 Se bulks.