Cu2SnS3 (CTS), a typical ternary copper-based sulfide, is considered as a potential p-type thermoelectric (TE) material with the advantages of environmental friendliness and low cost, but its performance is limited by the high lattice thermal conductivity and electrical resistivity. Herein, we have successfully synthesized undoped and In-doped CTS nanoparticles with a pure tetragonal phase by the colloidal method. More interestingly, plenty of twin boundaries appear in all the samples sintered from the synthesized nanoparticles independent of composition. The twin boundaries can effectively reduce the lattice thermal conductivity, while the tetragonal phase is beneficial to meliorate the electrical performance of CTS. Consequently, the highest zT reaches 0.36 at 700 K for Cu2Sn0.85In0.15S3, which is enhanced by 17 times compared to that of the pristine CTS with mainly the monoclinic phase. The tunable phase and microstructure via the colloidal method provide useful guidance to promote the performance of eco-friendly TE sulfides.

Multiple-band degeneracy has been widely recognized to be beneficial for high thermoelectric performance. Here, we discover that the p-type Dirac bands with lower degeneracy synergistically produce a higher Seebeck coefficient and electrical conductivity in topological semimetal BaAgBi. The anomalous transport phenomenon intrinsically originated from the asymmetric electronic structures: (i) complete p-type Dirac bands near the Fermi level facilitate high and strong energy-dependent hole relaxation time; (ii) the presence of additional parabolic conduction valleys allows for a large density of states to accept scattered electrons, leading to an enlarged hole–electron relaxation time ratio and, thus, weakened bipolar effect. In combination with the strong lattice anharmonicity, an exceptional p-type average ZT of 0.42 is achieved from 300 to 600 K, which can be dramatically enhanced to 1.38 via breaking the C 3v symmetry. This work uncovers the underlying mechanisms governing the abnormal transport behavior in Dirac semimetal BaAgBi and highlights the asymmetric electronic structures as target features to discover/design high-performance thermoelectric materials.

No abstract

No abstract

No abstract