High Thermoelectric Performance of In4Se3-Based Materials and the Influencing Factors

ConspectusMaterials that can directly convert electricity into heat, i.e., thermoelectric materials, have attracted renewed attention globally for sustainable energy applications. As one of the state-of-the-art thermoelectric materials, In4Se3 features an interesting crystal structure of quasi-two-dimensional sheets comprising In/Se chains that provide a platform to achieve a Peierls distortion and support a charge density wave instability. Single-crystal In4Se3−δ (δ = 0.65) shows strong anisotropy in its thermoelectric properties with a very high ZT of 1.48 at 705 K in the b–c plane (one of the highest values for an n-type thermoelectric material to date) but a much lower ZT of approximately 0.5 in the a–b plane. Because of the random dispersion of grains and the grain boundary effect, the electrical transport properties of polycrystalline In4Se3 are poor, which is the main impediment to improve their performance. The In4-site in the In4Se3 unit cell is substitutional for dopants such as Pb, which increa...