Resonant level-induced high thermoelectric response in indium-doped GeTe

Abstract

Resonant levels are promising for high-performance single-phase thermoelectric materials. Recently, phase-change materials have attracted much attention for energy conversion applications. As the energetic position of resonant levels could be temperature dependent, searching for dopants in phase-change materials, which can introduce resonant levels in both low and high temperature phases, remains challenging. In this study, possible distortions of the electronic density of states due to group IIIA elements (Ga, In, Tl) in GeTe are theoretically investigated. Resonant levels induced by indium dopants in both rhombohedral and cubic phase GeTe have been demonstrated. The experimental Seebeck coefficients of In x Ge 1 − x Te exhibit a large enhancement compared with those observed for other prior dopants. Indium dopants reduce the defect concentrations in GeTe, and thus, they lower the carrier concentrations and suppress the electronic component of the total thermal conductivity. The enhanced Seebeck coefficient, together with the suppressed thermal conductivity, leads to a reasonably high ZT of 1.3 at a temperature near 355°C in In 0.02 Ge 0.98 Te. The corresponding average ZT is enhanced by~70% across the entire temperature range of the rhombohedral and cubic phases. These observations indicate that indium-doped GeTe is a promising base material for achieving an even higher thermoelectric performance.

Manipulating the Ge Vacancies and Ge Precipitates through Cr Doping for Realizing the High‐Performance GeTe Thermoelectric Material

“…Temperature‐dependent thermoelectric transport properties for Cr doping samples Ge 1– x Cr x Te ( x = 0, 0.02, 0.03, 0.04, and 0.05): a) electrical resistivity, b) Seebeck coefficient, c) power factor, d) total thermal conductivity, e) lattice thermal conductivity of Ge 1– x Cr x Te (this work) in comparison with reported Ti x Ge 1– x Te, [ 52 ] In x Ge 1– x Te, [ 59 ] Mn x Ge 1– x Te, [ 43 ] Ag x Ge 1– x Te, [ 60 ] and f) figure of merit (ZT).…”

“…a) Room temperature carrier concentration‐dependent Seebeck coefficient for Cr doping and Cr‐Bi/Sb codoping samples, with a comparison to those of GeTe reported in literatures. [ 39,40,59,61–63 ] Temperature‐dependent electrical transport properties for all samples: b) Seebeck coefficient, c) electrical resistivity, and d) power factor.…”

Chalcogenide Thermoelectrics Empowered by an Unconventional Bonding Mechanism

“…In addition to valley degeneracy, resonant impurity levels that create distortions in the DOS near the Fermi energy can be employed to enhance the Seebeck coefficient. This strategy has been successfully introduced in Tl‐doped PbTe, Al‐doped PbSe, In‐doped SnTe, In‐doped GeTe, and Sn‐doped Bi 2 Te 3 . However, even though the Seebeck coefficient is enhanced by the enlarged , the carrier mobility is inevitably reduced because of the heavier charge carriers and enhanced resonant scattering …”

Thermoelectric performance of CuFeS2+2x composites prepared by rapid thermal explosion

“…Basically, a good thermoelectric material should have both a high Seebeck coefficient and electrical conductivity, and possess as low a thermal conductivity as possible. Currently, there are several families of excellent thermoelectric materials available, such as Bi 2 Te 3 12-15 , PbTe [16][17][18] , CoSb 3 19-21 , GeTe [22][23][24] , SnSe 25,26 and SnTe [27][28][29] . Although they all possess a highenergy conversion efficiency, most of them contain toxic and expensive elements.…”