Dynamic carrier transports and low thermal conductivity in n‐type layered InSe thermoelectrics

Abstract

AbstractSemiconductor InSe with wide bandgap and layered crystal structure is expected to be a promising thermoelectric material, and its excellent plasticity brings great potential applications in flexible and wearable thermoelectric devices. To advance its thermoelectric performance, this work systematically investigates the carrier and phonon transport properties in n‐type InSe. It is found that InSe compound presents an exceptional dynamic carrier transport property due to the amphoteric indium (In+ and In3+), which contributes to favorable temperature‐dependent increasing carrier concentration. More importantly, with S alloying in InSe, the carrier concentration can be further enhanced from ∼3.2 × 1013 cm–3 in InSe to ∼4.8 × 1015 cm–3 in InSe0.97S0.03 at 300 K, because S (χP ∼ 2.58) with larger Pauling electronegativity than Se (χP ∼ 2.55) can induce more In3+ state to increase carrier concentration in matrix. This boosted dynamic carrier transport property benefits an obviously enhanced power factor. Additionally, InSe compound presents intrinsically low thermal conductivity ∼1.6 W m–1 K–1 at 300 K due to low‐symmetry crystal structure and strong anharmonicity. This work indicates that the special dynamic carrier transport property and intrinsically low thermal conductivity in InSe make it as a worth‐expecting thermoelectric material.