Roles of Anion Sites in High‐Performance GeTe Thermoelectrics

Li, Meng; Xu, Shengduo; Hong, Min; Lyu, Wanyu; Wang, Yuan; Dargusch, Matthew; Zou, Jin; Cheng, Hui‐Ming; Chen, Huajun

doi:10.1002/adfm.202208579

Cited by 15 publications

(19 citation statements)

References 62 publications

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“…The bonding of V–Te (2.797 Å) is shorter than that of Ge–Te (3.005 Å) in C-GeTe, and electrons are localized after V doping, suggesting that Ge s electrons are reduced after V doping, and that V can reduce Δ E . Besides, Ta, Cu, Zn, Cr, La, and I are found to reduce the Δ E values of GeTe in our studies (Figure b). In this regard, the overall thermoelectric performance has been enhanced.…”

Section: Enhancing Electronic Transportmentioning

confidence: 99%

“…The experimental data points are also included. The sample with I doping leads to the highest B of ∼1.7, yielding an experimental zT of ∼2.5 at 700 K and the maximal theoretical maximal zT close to 3.0.…”

Section: Enhancing Electronic Transportmentioning

confidence: 99%

“…More importantly, the average zT ( zT avg ) over the studied temperature range for almost all GeTe materials is beyond 1.0 (Figure d). The highest zT avg is close to 1.8 in Ge 0.92 Bi 0.08 Te 0.92 I 0.08 . Values of ϕ is predicted using the finite elemental analysis (FEA) simulations.…”

Section: Introductionmentioning

confidence: 95%

“…The highest zT avg is close to 1.8 in Ge 0.92 Bi 0.08 Te 0.92 I 0.08 . 16 Values of ϕ is predicted using the finite elemental analysis (FEA) simulations. Figure 1e plots ϕ versus the temperature difference (ΔT) with the cold end temperature set as 300 K. The maximal ϕ reaches 18%, suggesting our materials are quite promising for thermoelectric applications.…”

Section: Introductionmentioning

confidence: 99%

“…The halogen I successfully reduces n and leads to optimized thermoelectric properties in GeTe. 16 Figure 1b shows a diagram for summarizing the developed strategies for enhancing thermoelectric performance based on the chemical principles and the accordingly developed GeTe materials. Specifically, the formation mechanism of defects in the pristine GeTe has been examined to guide the optimization of n and the minimization of carrier scattering.…”

Section: Introductionmentioning

confidence: 99%

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Chemistry in Advancing Thermoelectric GeTe Materials

Hong

Chen

2022

Acc. Chem. Res.

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Metrics & MoreArticle Recommendations CONSPECTUS:The ever-growing energy crisis and the deteriorated environment caused by carbon energy consumption motivate the exploitation of alternative green and sustainable energy supplies. Because of the unique advantages of zero-emission, no moving parts, accurate temperature control, a long steady-state operation period, and the ability to operate in extreme situations, thermoelectrics, enabling the direct conversion between heat and electricity, is a promising and sustainable option for power generation and refrigeration. However, with increasing application potentials, thermoelectrics is now facing a major challenge: developing high-performance, Pb-free, and lowtoxic thermoelectric materials and devices.As one group of promising candidates, GeTe derivatives have the potential to replace the widely used thermoelectric materials containing highly toxic elements.In this Account, we summarize our recent progress in developing highperformance GeTe-based thermoelectric materials via exploring innovative strategies to enhance electron transports and dampen phonon propagations. First, we fundamentally illustrate the underlying chemistry and physical reason for an intrinsically high carrier concentration in GeTe, which enormously restrains the thermoelectric performance of GeTe. From our theoretical calculations, the formation energy of Ge vacancy is the lowest among the defects in GeTe, energetically favoring Ge vacancies in the lattice and leading to intrinsically high carrier concentrations. Accordingly, aliovalent doping/alloying is proposed to increase the formation energy of Ge vacancies and decrease the carrier concentration to the optimal level. We then outline the newly developed method to refine the band structures of GeTe with tuned electronic transport. On the basis of the molecular orbital theory, the energy offset between two valence band edges at the L and Σ points in GeTe should be ascribed to the slightly different Ge_4s orbital characters at these two points, which guides the screening of dopants for band convergence. Besides, the Rashba spin splitting is explored to increase the band degeneracy of GeTe. Afterward, we analyze the dampened phonon propagation in GeTe to minimize its lattice thermal conductivity. Alloying with the heavy Sb atoms can shift the optical phonon modes toward low frequency and reinforce the interaction of optical and acoustic phonon modes so that the inherent phonon scattering is enhanced. In addition, planar vacancies and superlattice precipitates can significantly strengthen phonon scattering to result in ultralow lattice thermal conductivity. After that, we overview the finite elemental analysis simulations to optimize the device geometry for maximizing the device performance and introduce the as-developed prototype GeTe-based thermoelectric device. In the end, we point out future directions in the development of GeTe for device applications. The strategies summarized in this Account can serve as references for developing wide materi...

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Section: Enhancing Electronic Transportmentioning

confidence: 99%

Section: Enhancing Electronic Transportmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Chemistry in Advancing Thermoelectric GeTe Materials

Hong

Chen

2022

Acc. Chem. Res.

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In Situ Design of High‐Performance Dual‐Phase GeSe Thermoelectrics by Tailoring Chemical Bonds

Duan

Lyu

et al. 2023

Adv Funct Materials

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Composite engineering favors high thermoelectric performance by tuning the carrier and phonon transport. Herein, orthorhombic and rhombohedral dualphase GeSe are designed in situ by tailoring chemical bonds. Atom probe tomography verifies the coexistence of a covalently bonded orthorhombic phase and a metavalently bonded rhombohedral phase in GeSe-InTe alloys. The production of the rhombohedral phase simultaneously increases the carrier concentration, the carrier mobility, the band degeneracy, and the density-of-states effective mass due to the reduced formation energy of cation vacancies and the improved crystal symmetry. These attributes are beneficial to a high-power factor. In addition, the thermal conductivity can be significantly reduced due to the intrinsically strong lattice anharmonicity of the metavalently bonded phase, the interfacial acoustic phonon mismatch across different bonding mechanisms, and the phonon scattering at vacancy-solute clusters. Moreover, the metavalently bonded phase embraces higher solubility of dopants that enables the further optimization of properties by Cd-Ag doping, resulting in a zT of 0.95 at 773 K as well as enhanced strength and ductility in dual-phase Ge 0.94 Cd 0.03 Ag 0.03 Se(InTe) 0.15 . This work indicates that in situ design of dual-phase composites by tailoring chemical bonds is an effective method for enhancing the thermoelectric and mechanical properties of GeSe and other p-bonded chalcogenides.

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Trends in GeTe Thermoelectrics: From Fundamentals to Applications

Li,

Shi,

Chen

2024

Adv Funct Materials

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Germanium telluride (GeTe) with ultrafast ferroelectric transition, Rashba‐like electronic transport, and anomalous phonon anharmonicity are historically studied for potential memorizing and thermoelectric applications. Due to recent breakthroughs in spintronics, valleytronics, orbitronics, pre‐eminent GeTe thermoelectrics have re‐attracted enormous interest from both academia and industries, with increasing reports of significant figure‐of‐merit over 2.7 and the maximum efficiency of up to 17.0%. Here, the emerging trends in advancing GeTe thermoelectrics, starting from fundamentals of phase transformation, crystal structure, bonding mechanisms, and transport characteristics, with a highlight on the roles of Ge_4s2 lone pairs, are timely overviewed. Technical insights in synthesis, characterization, property measurement, and computation are then summarized. After that, several innovative strategies for increasing the figure‐of‐merit, including entropy engineering, nanostructuring, and hybridization, which will further benefit near‐room‐temperature and n‐type performance, are examined. Moreover, high‐density and high‐efficiency devices with broad working temperatures are discussed as a result of rational configurational and interfacial design. In the end, perspective remarks on the challenges and outlook envisaging for next‐generation GeTe thermoelectrics, which will play a prominent role in future energy and environmental landscapes, are provided.

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Roles of Anion Sites in High‐Performance GeTe Thermoelectrics

Cited by 15 publications

References 62 publications

Chemistry in Advancing Thermoelectric GeTe Materials

Chemistry in Advancing Thermoelectric GeTe Materials

In Situ Design of High‐Performance Dual‐Phase GeSe Thermoelectrics by Tailoring Chemical Bonds

Trends in GeTe Thermoelectrics: From Fundamentals to Applications

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