Chemical Potential Tuning and Enhancement of Thermoelectric Properties in Indium Selenides

Abstract

Researchers have long been searching for the materials to enhance thermoelectric performance in terms of nano scale approach in order to realize phonon-glass-electron-crystal and quantum confinement effects. Peierls distortion can be a pathway to enhance thermoelectric figure-of-merit ZT by employing natural nano-wire-like electronic and thermal transport. The phonon-softening known as Kohn anomaly, and Peierls lattice distortion decrease phonon energy and increase phonon scattering, respectively, and, as a result, they lower thermal conductivity. The quasi-one-dimensional electrical transport from anisotropic band structure ensures high Seebeck coefficient in Indium Selenide. The routes for high ZT materials development of In4Se3−δ are discussed from quasi-one-dimensional property and electronic band structure calculation to materials synthesis, crystal growth, and their thermoelectric properties investigations. The thermoelectric properties of In4Se3−δ can be enhanced by electron doping, as suggested from the Boltzmann transport calculation. Regarding the enhancement of chemical potential, the chlorine doped In4Se3−δCl0.03 compound exhibits high ZT over a wide temperature range and shows state-of-the-art thermoelectric performance of ZT = 1.53 at 450 °C as an n-type material. It was proven that multiple elements doping can enhance chemical potential further. Here, we discuss the recent progress on the enhancement of thermoelectric properties in Indium Selenides by increasing chemical potential.

Thermoelectric Enhancement of Different Kinds of Metal Chalcogenides

“…[81] The Peierls distortion and charge density wave could also lead to decreased thermal conductivity. [82] In the SnX and In 4 Se 3 systems, due to the off-stoichiometric valence of elements, an excess amount of charge carriers usually exists, for example, the hole concentration of SnTe is over 10 21 cm -3 . [83] Thus, the Se vacancies or element doping could simultaneously adjust the band structure and the carrier concentrations.…”

“…[15,[82][83][84] Simultaneously, the weak van der Waals bonding between the adjacent layers (along the a-axis) is helpful for reducing the thermal conductivity. Due to the combination of these factors, single crystals of SnSe and In 4 Se 3-x showed excellent thermoelectric performance, with a ZT of 2.6 at 923 K (p-type) and 1.48 at 705 K (n-type), respectively.…”

“…The semiconductor type band structure changes into a semi‐metallic band with a deficiency of Se, and there is a flat band along the X–Γ and Y–S symmetry lines, indicating that the holes in the b ‐direction are highly localized . The Peierls distortion and charge density wave could also lead to decreased thermal conductivity . In the SnX and In 4 Se 3 systems, due to the off‐stoichiometric valence of elements, an excess amount of charge carriers usually exists, for example, the hole concentration of SnTe is over 10 21 cm −3 .…”

“…The thermoelectric performance of Sn–X and In–X can be further enhanced by the off‐stoichiometric element ratio or doping effects, such as excess amount of Sn and deficiency of Se . Simultaneously, the weak van der Waals bonding between the adjacent layers (along the a ‐axis) is helpful for reducing the thermal conductivity.…”

Improvement in Thermoelectric Properties by Tailoring at In and Te Site in In2Te5

“…In 4 Se 3 exhibit unique two dimensional crystalline sheets layered structure with weak van der Walls interactions containing charge density wave which is involved with low dimensional transport phenomena rendered lattice distortion (Peierls distortion). An enhanced phonon scattering greatly reduces thermal conductivity [10,11,12] and In 4 Te 3 materials are 0.42 eV and 0.29 eV at room temperature respectively indicating that both compounds behave as semiconductors [8]. In 2 Te 5 is an interesting system having a layered structure [10,[12][13][14].…”