Atomic-scale tuning of oxygen-doped Bi2Te2.7Se0.3 to simultaneously enhance the Seebeck coefficient and electrical conductivity†
Manipulation of oxygen-related impurities is an extreme challenge for most of the thermoelectric materials, especially for those possessing nanostructures, since they normally result in the degradation of the thermoelectric performance. Here, we demonstrate that by atomic-scale controlling of oxygen doping in the form of dislocation clusters in Bi2Te2.7Se0.3 (BTS) thermoelectric materials, the trade-off between the Seebeck coefficient and electrical conductivity is broken, resulting in the simultaneously enhanced Seebeck coefficient and electrical conductivity and the suppressed thermal conductivity. As a consequence, a maximum ZT of 0.91 is achieved, which is approximately 1.4 times higher than that of pristine BTS. Based on HR-STEM investigation, the oxygen-related dislocation clusters can be unambiguously identified and we argue that the optimized carrier/phonon transport behavior can be attributed to the multifunctionality of oxygen-related dislocation clusters in BTS acting as electron donors, electron energy filters and phonon blockers. Our work provides a clear microscopic understanding on the role of oxygen doping in modifying phonon/carrier transport behavior in BTS thermoelectric materials, which provides an efficient avenue for designing high performance thermoelectric materials.