An Update Review on N-Type Layered Oxyselenide Thermoelectric Materials

Zheng, Junqing; Wang, Dongyang; Zhao, Li‐Dong

doi:10.3390/ma14143905

Cited by 12 publications

(3 citation statements)

References 80 publications

(154 reference statements)

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“…At the G point, the valence band valleys near the Fermi energy are strongly localized, while the conduction band valleys are relatively dispersed. The effective energy valence band valleys exhibit higher degeneracy than those in the conduction band [39], which could enhance material properties such as thermoelectric efficiency [40][41][42]. The thermoelectric efficiency of the material is characterized by a quality factor ZT = TS 2 σ/κ, where T is temperature, S is Seebeck coefficient, σ is electrical conductivity, and κ is thermal conductivity.…”

Section: Resultsmentioning

confidence: 99%

“…It is important that thermoelectricity and conductivity can be influenced when the actual Fermi energy (E F ) differs from the predicted E . F DET If the Fermi level enters the VBM [41] or CBM [42], additional energy bands can be involved in electrical transport, thereby enhancing the degeneracy of the energy band valley and improving thermoelectricity and conductance of the material. On the other hand, if the Fermi level is far from the VBM or CBM, the number of effective energy bands near the Fermi surface will decrease, resulting in a decrease of carrier concentration near the Fermi surface and deterioration of thermoelectricity and conductivity.…”

Section: Resultsmentioning

confidence: 99%

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Electronic properties and passivation mechanism of AlGaN/GaN heterojunction with vacancies: a DFT study

et al. 2023

Phys. Scr.

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A significant issue for GaN-based high-electron-mobility transistors (HEMTs) in high power devices is the material defect, particularly the defect states generated by the defects, which has a negative impact on the device carrier concentration and carrier transport. Based on density functional theory (DFT), we investigate the microscopic properties of different type point vacancies in the AlGaN/GaN heterojunction. It is found that N vacancy introduces defect states near the conduction band minimum (CBM) of the GaN layer and AlGaN/GaN interface. Ga and Al vacancies introduce defect states near the valence band maximum (VBM) in bulk and interface of AlGaN/GaN heterojunction. Moreover, Al vacancy is more likely to be an effective candidate for acceptor defect than Ga vacancy. We further study several AlGaN/GaN interface passivation schemes by introducing F, V group element P, and III group element B at the AlGaN/GaN heterojunction interface to analyze the passivation mechanism. According to the results of the passivation models, B passivation of Ga and Al vacancies is an effective method to completely remove the defect states from Ga and Al vacancy defects. Combining the III and V groups elements into the passivated process may be effective in achieving high-quality AlGaN/GaN heterojunction interface for the future GaN-based HEMTs fabrication.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Electronic properties and passivation mechanism of AlGaN/GaN heterojunction with vacancies: a DFT study

et al. 2023

Phys. Scr.

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“…As shown in Fig. 4 A, BCSO inherently has extremely low κ due to its special quasi-superlattice layered structure and large Grüneisen parameters caused by Bi 3+ lone pair electrons and the local vibration of Cu + [ 52 ]. When O is substituted by Se, the κ of the S-BCSO sample is reduced due to the generation of a large number of dislocations, which complements the scattering of mid-frequency phonons (M-P).…”

Section: Resultsmentioning

confidence: 99%

Realizing Plain Optimization of the Thermoelectric Properties in BiCuSeO Oxide via Self-Substitution-Induced Lattice Dislocations

Xu¹,

Chen

Li³

et al. 2023

Research

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Seeking new strategies to tune the intrinsic defect and optimize the thermoelectric performance via no or less use of external doped elements (i.e., plain optimization) is an important method to realize the sustainable development of thermoelectric materials. Meanwhile, creating dislocation defects in oxide systems is quite challenging because the rigid and stiff ionic/covalent bonds can hardly tolerate the large strain energy associated with dislocations. Herein, taking BiCuSeO oxide as an example, the present work reports a successful construction of dense lattice dislocations in BiCuSeO by self-doping of Se at the O site (i.e., Se O self-substitution), and achieves plain optimization of the thermoelectric properties with only external Pb doping. Owing to the self-substitution-induced large lattice distortion and the potential reinforcement effect by Pb doping, high-density (about 3.0 × 10 14 m −2 ) dislocations form in the grains, which enhances the scattering strength of mid-frequency phonon and results in a substantial low lattice thermal conductivity of 0.38 W m −1 K −1 at 823 K in Pb-doped BiCuSeO. Meanwhile, Pb Bi doping and Cu vacancy markedly improve the electrical conductivity while maintaining a competitively high Seebeck coefficient, thereby contributing to a highest power factor of 942 μW m −1 K −2 . Finally, a remarkably enhanced zT value of 1.32 is obtained at 823 K in Bi 0.94 Pb 0.06 Cu 0.97 Se 1.05 O 0.95 with almost compositional plainification. The high-density dislocation structure reported in this work will also provide a good inspiration for the design and construction of dislocations in other oxide systems.

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Microstructure Optimization in the Shear‐Exfoliated Bi₆Cu₂Se₄O₆ through Introducing Reduced Graphene Oxide Leads to Wide‐Ranged Thermoelectric Performance

Zheng,

Wen,

Wang

et al. 2024

Adv Funct Materials

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Bi6Cu2Se4O6 is considered as an ideal n‐type thermoelectric material to pair with p‐type BiCuSeO for preparing oxyselenide‐based thermoelectric devices, but its thermoelectric performance is limited by poor electrical conductivity. In this research, the reduced graphene oxide (rGO) nanosheets are introduced into Bi6Cu2Se3.6Cl0.4O6 matrix through liquid‐phase shear exfoliation to modify the microstructure. rGO can insert into matrix grains as intercalations, or embed into grain boundaries as wetting phase, and prompt grain alignment, which contributes to the significantly enhanced carrier mobility, thus leading to an improvement in electrical conductivity from ≈15 S cm−1 to ≈230 S cm−1 at 303 K. Whereafter, the effective donor dopant Nb is chosen to substitute Bi. The carrier concentration is increased without damaging the carrier mobility, resulting in a further improved electrical conductivity of ≈840 S cm−1 at 303 K. Lattice thermal conductivity is also suppressed owing to the intensive phonon scattering by point defects and grain boundaries. Ultimately, a record‐breaking peak ZT ≈0.5 (873 K) and average ZT ≈0.3 (303–873 K) can be achieved in Bi5.91Nb0.09Cu2Se3.6Cl0.4O6 + 0.5% rGO. The microstructure optimization method in this research effectively improves thermoelectric performance, and is anticipated to be applied in other thermoelectrics.

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An Update Review on N-Type Layered Oxyselenide Thermoelectric Materials

Cited by 12 publications

References 80 publications

Electronic properties and passivation mechanism of AlGaN/GaN heterojunction with vacancies: a DFT study

Electronic properties and passivation mechanism of AlGaN/GaN heterojunction with vacancies: a DFT study

Realizing Plain Optimization of the Thermoelectric Properties in BiCuSeO Oxide via Self-Substitution-Induced Lattice Dislocations

Microstructure Optimization in the Shear‐Exfoliated Bi₆Cu₂Se₄O₆ through Introducing Reduced Graphene Oxide Leads to Wide‐Ranged Thermoelectric Performance

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An Update Review on N-Type Layered Oxyselenide Thermoelectric Materials

Cited by 12 publications

References 80 publications

Electronic properties and passivation mechanism of AlGaN/GaN heterojunction with vacancies: a DFT study

Electronic properties and passivation mechanism of AlGaN/GaN heterojunction with vacancies: a DFT study

Realizing Plain Optimization of the Thermoelectric Properties in BiCuSeO Oxide via Self-Substitution-Induced Lattice Dislocations

Microstructure Optimization in the Shear‐Exfoliated Bi6Cu2Se4O6 through Introducing Reduced Graphene Oxide Leads to Wide‐Ranged Thermoelectric Performance

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Product

Resources

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Microstructure Optimization in the Shear‐Exfoliated Bi₆Cu₂Se₄O₆ through Introducing Reduced Graphene Oxide Leads to Wide‐Ranged Thermoelectric Performance