Achieving Ultralow Lattice Thermal Conductivity and High Thermoelectric Performance in GeTe Alloys via Introducing Cu₂Te Nanocrystals and Resonant Level Doping

Abstract

The binary compound of GeTe emerging as a potential medium-temperature thermoelectric material has drawn a great deal of attention. Here, we achieve ultralow lattice thermal conductivity and high thermoelectric performance in In and a heavy content of Cu codoped GeTe thermoelectrics. In dopants improve the density of state near the surface of Femi of GeTe by introducing resonant levels, producing a sharp increase of the Seebeck coefficient. In and Cu codoping not only optimizes carrier concentration but also substantially increases carrier mobility to a high value of 87 cm 2 V −1 s −1 due to the diminution of Ge vacancies. The enhanced Seebeck coefficient coupled with dramatically enhanced carrier mobility results in significant enhancement of PF in Ge 1.04−x−y In x Cu y Te series. Moreover, we introduce Cu 2 Te nanocrystals' secondary phase into GeTe by alloying a heavy content of Cu. Cu 2 Te nanocrystals and a high density of dislocations cause strong phonon scattering, significantly diminishing lattice thermal conductivity. The lattice thermal conductivity reduced as low as 0.31 W m −1 K −1 at 823 K, which is not only lower than the amorphous limit of GeTe but also competitive with those of thermoelectric materials with strong lattice anharmonicity or complex crystal structures. Consequently, a high ZT of 2.0 was achieved for Ge 0.9 In 0.015 Cu 0.125 Te by decoupling electron and phonon transport of GeTe. This work highlights the importance of phonon engineering in advancing high-performance GeTe thermoelectrics.

A high-efficiency GeTe-based thermoelectric module for low-grade heat recovery

“…The sharp decrease of carrier concentration in (GeTe) 1Àx (CuI) x is mainly due to the disappearance of the Ge vacancy layer, which has also been found in previous studies. 27,28,43,44 At the same time, CuI doping also improves the mobility of GeTe. This can be understood by the reduction of Ge vacancies/precipitates for a weak charge carrier scattering by impurities.…”

“…2f, the roomtemperature power factor of the CuI-Bi codoped GeTe in this work is higher than most of the literature results. 27,35,37,44,45 The total thermal conductivity k, electronic thermal conductivity k e , and lattice conductivity k l from 300 to 800 K for the (GeTe) 1Àx (CuI) x (x ¼ 0, 0.02, 0.04) and (Ge 1Ày Bi y Te) 0.96 (-CuI) 0.04 (y ¼ 0.02, 0.04, 0.06) samples are shown in Fig. 4a-c.…”

“…2f, the room-temperature power factor of the CuI–Bi codoped GeTe in this work is higher than most of the literature results. 27,35,37,44,45…”

Realization of high thermoelectric performance in solution-synthesized porous Zn and Ga codoped SnSe nanosheets

“…However, the intricate interrelationship between these parameters makes it challenging to optimize the electrical and thermal transport properties simultaneously. Many approaches including but not limiting to band convergency, [5][6][7] resonating level, 8,9 highentropy design, 10,11 energy ltering effect, 12,13 lattice imperfection [14][15][16] and nanostructure design [17][18][19] have been proved to be effective in improving thermoelectric performance.…”

Synergistically Optimized Carrier and Phonon Transport Properties in Bi–Cu2S Coalloyed GeTe

“…That is to say, achieving a delicate balance among the carrier concentration, carrier mobility, and thermal conductivity. Very recently, the doping of Cu was adopted to realize a good balance between the carrier concentration and carrier mobility, leading to high weighted mobility and ZT values. , These works motivate us to further promote the TE properties of GeTe-based materials through the coalloying of a Bi and Cu-based compound.…”