Thermoelectric Performance Research Articles

Synergistic Suppression of Bipolar Effect and Lattice Thermal Conductivity Leading to High Average Figure of Merit in Bi0.4Sb1.6Te3 Materials through Alloying with AgSbTe2.

Bismuth telluride-based materials have been widely used in commercial thermoelectric applications due to their excellent thermoelectric performance in the near-room-temperature range, yet further improvement of their thermoelectric properties is still necessary. Moreover, the narrow band gap of these materials results in a bipolar effect at elevated temperatures, which causes severe degradation of the thermoelectric performance. In this work, the commercial Bi0.4Sb1.6Te3 was alloyed with AgSbTe2 by using high-energy ball milling method combined with spark plasma sintering. It was found that ball milling can effectively reduce the lattice thermal conductivity of the samples. The alloying of AgSbTe2 leads to a gradual increase in hole carrier concentration, resulting in an enhanced electrical conductivity and optimized power factor. Additionally, the bipolar effect is also weakened due to the increased hole carrier concentration. Furthermore, the substitution of Ag in the Bi/Sb sublattice causes further reduction in the lattice thermal conductivity. Ultimately, the sample alloyed with 0.15 wt % AgSbTe2 demonstrates its best thermoelectric performance with a maximum zT of 1.35 at 393 K, showing a 20.5% improvement compared to the commercial sample. Besides, its average zT reaches a high value of 1.25 between 303 and 483 K, with a 27.6% improvement compared to that of the commercial sample.

Controlling the Thermoelectric Performance of Doped Naphthobisthiadiazole-Based Donor-Acceptor Conjugated Polymers through Backbone Engineering.

This study investigates backbone engineering and evaluates the thermoelectric properties of FeCl3-doped naphthobisthiadiazole (NTz)-based donor-acceptor (D-A) conjugated polymer films. The NTz acceptor unit is coupled with three distinct donor units, namely dialkylated terthiophene (3T), dialkylated quaterthiophene (4T), and dialkylated bisthienyl thienothiophene (2T-TT) to yield copolymers designated as PNTz3T, PNTz4T, and PNTzTT. The difference in donor units leads to diverse molecule stacking and electronic properties, which can be systematically discovered via the three polymers. The linear structure of PNTz4T enables an orderly arrangement of side chains, thereby promoting dopant intercalation for enhanced carrier concentration. Additionally, this linear structure leads to an edge-on stacking mode, thereby improving the in-plane carrier mobility. As a result, the doped PNTz4T exhibits the highest electrical conductivity (σ) of 88.3 S cm-1 along with a Seebeck coefficient (S) of 62.2 µV K-1, thereby achieving the highest power factor (PF) of 34.2 µW m-1 K-2. These results highlight the relationship between the molecular design, microstructure, and doping effects in manipulating the thermoelectric performance of doped NTz-based D-A polymers.

Optimization of Thermoelectric Performance of Ag2Te Films via a Co-Sputtering Method.

Providing self-powered energy for wearable electronic devices is currently an important research direction in the field of thermoelectric (TE) thin films. In this study, a simple dual-source magnetron sputtering method was used to prepare Ag2Te thin films, which exhibit good TE properties at room temperature, and the growth temperature and subsequent annealing process were optimized to obtain high-quality films. The experimental results show that films grown at a substrate temperature of 280 °C exhibit a high power factor (PF) of ~3.95 μW/cm·K2 at room temperature, which is further improved to 4.79 μW/cm·K2 after optimal annealing treatment, and a highest PF of ~7.85 μW/cm·K2 was observed at 200 °C. Appropriate annealing temperature effectively increases the carrier mobility of the Ag2Te films and adjusts the Ag/Te ratio to make the composition closer to the stoichiometric ratio, thus promoting the enhancement of electrical transport properties. A TE device with five legs was assembled using as-fabricated Ag2Te thin films. With a temperature difference of 40 K, the device was able to generate an output voltage of approximately 14.43 mV and a corresponding power of about 50.52 nW. This work not only prepared a high-performance Ag2Te film but also demonstrated its application prospects in the field of self-powered electronic devices.

Computational insights into transition metal-based BaCoX3 (X = Cl, Br, I) halide perovskites for spintronics, photovoltaics, and renewable energy devices

Ab-initio simulations using density functional theory (DFT) were employed to investigate the structural, mechanical, electronic, magnetic, optical, and thermoelectric properties of halide perovskites \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {BaCoX}_3$$\\end{document} (X = Cl, Br, I). Structural optimization and mechanical stability assessments confirm the reliability of these perovskites in a hexagonal P\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$6_3$$\\end{document}mc symmetry. The stability of the ferromagnetic phase was validated through total crystal energy minimization via Murnaghan’s equation of state. Electronic band structures and density of states, derived from the generalized gradient approximation (GGA), reveal a semiconducting ferromagnetic nature in the spin up channel, spotlighting their potential in semiconductor spintronic applications. Phonon dispersion analysis of \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {BaCoCl}_3$$\\end{document} and \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {BaCoBr}_3$$\\end{document} revealed positive phonon modes throughout the entire Brillouin zone, confirming their dynamical stability. In contrast, \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {BaCoI}_3$$\\end{document} demonstrated dynamical instability. The elastic constants confirm the mechanical stability and ductile nature of the perovskites. Optical and dielectric properties of these perovskites show significant UV absorption and photoconductivity, making them highly suitable for optoelectronic and solar cell applications. Finally, transport properties, such as the Seebeck coefficient, electrical conductivity, thermal conductivity, power factor, and figure of merit (ZT) unveil their exceptional thermoelectric performance. Combining half-metallic ferromagnetic traits with superior thermoelectric and optoelectronic performance positions \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {BaCoX}_3$$\\end{document} compounds as exceptional candidates for applications in spintronics, optoelectronics, and thermoelectrics. This comprehensive investigation demonstrates their ability to excel across a diverse array of advanced technological applications.

Machine Learning and First-Principle Predictions of Materials with Low Lattice Thermal Conductivity.

We performed machine learning (ML) simulations and density functional theory (DFT) calculations to search for materials with low lattice thermal conductivity, κL. Several cadmium (Cd) compounds containing elements from the alkali metal and carbon groups including A2CdX (A = Li, Na, and K; X = Pb, Sn, and Ge) are predicted by our ML models to exhibit very low κL values (<1.0 W/mK), rendering these materials suitable for potential thermal management and insulation applications. Further DFT calculations of electronic and transport properties indicate that the figure of merit, ZT, for the thermoelectric performance can exceed 1.0 in compounds such as K2CdPb, K2CdSn, and K2CdGe, which are therefore also promising thermoelectric materials.

Skutterudites as sustainable thermoelectric material- A critical review

In this article, we comprehensively reviewed the thermoelectric proper- ties of skutterudites-based materials. We discussed the various synthesis methods like non-chemical and chemical methods for the synthesis of the skutterudites materials for thermoelectric applications. In particular, this review articles also consolidates the information on how the filler plays a crucial role in improving the thermoelectric performance of the skutterudites materials. In addition, this review also concentrates on diverse fabrication methods employed in the production of skutterudites to optimize their thermoelectric performance. It also elucidates the efficiency of devices based on skutterudite materials and discusses the applications of thermoelectric devices.

Improved thermoelectric performance of α- and β- Cu2Se through suppression of hole density using extrinsic copper vacancies

Modulating Cu+ ion disorder in Cu2Se can enable control over the polymorphism and the carrier density leading to enhanced thermoelectric properties for both α- and β-Cu2Se. Here we report that the incorporation of Cr3+ into the Cu2Se crystal lattice facilitates the stabilization of α-Cu2Se at 300 K leading to a large (∼140%) reduction in the carrier density both below and above the phase transition. This is attributed to the reduction in the density of intrinsic copper interstitials (Cui∙) within the Cu(2-δ-λ)(CrCu..)λ(VCu′)δ(Cuix)δ-2λ(h∙)δ-2λSe crystal lattice. Such optimization of the carrier density led to a large (63%) increase in the thermopower and a drastic (46%) reduction in the total thermal conductivity for both α- and β-Cu2Se matrices. Consequently, a significant enhancement of the thermoelectric performance is observed in the entire temperature range from 300 K to 773 K. This results in high average ZT values for both α-Cu2Se (ZTave = 0.60) and β-Cu2Se (ZTave = 0.97), which paves the way for both near room temperature and high temperatures applications. This work provides a new approach to optimize the thermoelectric performance of Cu2Se-based materials by leveraging the interaction between mobile intrinsic Cui. and extrinsic VCu′ to suppress the hole density.

Synergistic effect of indium doping on thermoelectric performance of cubic GeTe-based thin films

Germanium Telluride (GeTe) has been widely explored as a promising lead-free thermoelectric material in its rhombohedral and cubic phases. However, the structural transition between these two phases at ∼700 K causes an abrupt change of thermal expansion coefficient, challenging its broader practical applications. Also, as characterized by multi-valence bands and strong anharmonic interaction, the high-temperature cubic phase exhibits a higher power factor, lower thermal conductivity, and ultimately superior thermoelectric performance than its rhombohedral counterpart. Prompted by these, in this work, the cubic phase of Ge0.9Sb0.1Te (presented as GeSbTe in the following content) nanocrystalline thin film is successfully realized by RF sputtering followed by post-annealing treatment. Additionally, Indium, as an electron donor to the germanium site and an effective scattering center, further moderates carrier concentration, enhances the Seebeck coefficient and reduces thermal conductivity. The optimal composition achieves an estimated peak of ∼1.95 and an estimated average of ∼ 1.11 within the temperature range of 300 K to 575 K, showcasing GeTe as a compelling candidate for applications close to room temperature.

Reduced Thermal Conductivity of Constricted Graphene Nanoribbons for Thermoelectric Applications

Graphene nanoribbons (GNRs) hold promise as thermoelectric (TE) materials due to their advantageous electronic properties compared to conventional candidates. However, a key challenge to enhancing the TE performance of GNRs lies in reducing the thermal conductivity while maintaining the electronic transport properties. To address this challenge - this study proposes a GNR-based structure featuring nanoscale constrictions named graphene nano constrictions (GNCs). This work systematically analyzes the thermal transport properties of these GNCs and compares them to conventional GNRs. Non-Equilibrium Molecular Dynamics (NEMD) simulations were employed to evaluate the lattice thermal conductivity of the material, and a marked reduction of thermal conductivity exceeding 74% was observed in the proposed structures. Furthermore, it is revealed that the thermal conductivity of these structures can be further tailored by manipulating their physical geometry, focusing on the length and the constriction dimensions. Additionally, superlattice counterparts of the GNCs composed of graphene and h-BN are explored in this study. Subsequently, an 88% reduction of lattice thermal conductivity is observed in the superlattice counterparts of GNCs compared to GNRs. Overall, this study demonstrates the effectiveness of nanoscale constrictions in manipulating the thermal conductivity of GNR-based structures, creating a path for optimizing their TE performance and potential device applications.

Advancement in the Thermoelectric Performance of Bulk SnSe: GGA+U Approach for Band Gap Calculation and Strain Induced Thermal Conductivity

Advancement in the Thermoelectric Performance of Bulk SnSe: GGA+U Approach for Band Gap Calculation and Strain Induced Thermal Conductivity

Achieving low thermal conductivity and high quality factor in sextuple-doped TiS2

Transition-metal dichalcogenide TiS2 stands out as a sustainable candidate for room- and medium-temperature thermoelectric materials due to its affordability, non-toxicity, eco-friendly nature and use of non-critical elements. However, its light element compositional nature results in a large thermal conductivity, which is the main limitation of the thermoelectric performance of TiS2. Here, we report a multi-element doping strategy by incorporating equivalent (Se, Zr) elements and introducing higher-valence (Nb, Ta) and lower-valence (Y, La) elements in pairs to minimize its lattice thermal conductivity, κlat. The findings indicate a nearly 50% decrease in κlat across the entire temperature range, attributed to the presence of strong point-defect scattering after multi-element doping. Additionally, we observed a reduced dependency of κlat on temperature in multi-element doped TiS2, as point defects can effectively scatter phonons at room temperature. As a result, the multi-element doped TiS2 attained its highest ZT value of approximately 0.4 at 625 K. Incorporating higher-valence and lower-valence elements in pairs proves to be an effective method for decreasing lattice thermal conductivity without compromising too much of its large Seebeck coefficient.

Enhancement of thermoelectric transport in surface halogenated Ti2O MOenes via electron–phonon drag effect

Designing efficient and environmentally friendly thermoelectric materials near room temperature is critical, and the electron–phonon drag effect on thermoelectric transport in monolayers remains largely unexplored. This manuscript systematically investigates the electron–phonon drag effect in surface halogenated Ti2O MOenes (Ti2OX2, X = F, Cl) by solving fully coupled electron–phonon Boltzmann transport equations. We find that the phonon drag effect significantly enhances the total Seebeck coefficient and various electronic transport coefficients, including the thermal response of electrons to an electric field, electrical conductivity, and electronic thermal conductivity at zero field, while the electron drag effect notably increases the lattice thermal conductivity, especially at high carrier concentrations and low temperatures. Furthermore, the electron–phonon drag effect significantly increases the thermoelectric figure of merit (zT) across 100–––900 K, with the greatest enhancement at low temperatures. At room temperature, zT increases by 13.73 times for Ti2OF2 and 2.82 times for Ti2OCl2, achieving maximum values of 0.92 and 0.84, respectively. Our work underscores the superior thermoelectric performance of surface halogenated Ti2O MOenes near room temperature and the potential of leveraging electron–phonon drag effects to enhance the electrical, thermal and thermoelectric transport in monolayers.

First-principles insights into thermoelectric behavior of XNiAs (X = Sc, Y) half-Heusler compounds

Abstract Half-Heusler (HH) compounds are regarded as potential candidates for thermoelectric devices to convert waste heat energy into electrical power, which could help mitigate the ongoing energy crisis. In this study, we investigate the structural, electronic, magnetic, and thermoelectric properties of HH compounds XNiAs (X = Sc, Y) using Density Functional Theory (DFT) and semi-classical Boltzmann transport theory (BTE). The compounds are non-magnetic semiconductors with an indirect band gap of 0.48 ( 0.50) eV for ScNiAs (YNiAs) respectively. Both materials show dynamic and mechanical stability, with ScNiAs displaying brittleness and YNiAs exhibiting ductility. At room temperature, the lattice thermal conductivity (κ l ) for ScNiAs is 28.67 W/mK, while for YNiAs, it is 15.21 W/mK and both decrease as the temperature rises. The highest value of power factors is 29.03 μW/cmK2 and 29.74 μW/cmK2 for ScNiAs and YNiAs respectively at 1100 K for n-type doping. The optimal values of the figure of merit (zT) for n-type doping are 0.33 for ScNiAs and 0.58 for YNiAs at 1100 K. Both compounds exhibit better thermoelectric performance for n-type doping compared to p-type doping. The presence of flat bands and higher κ l limits these materials from achieving higher zT values.

Enhanced Thermoelectric Properties in Cu₁.₈Se Thin Films: Achieving Superior Power Factor through Phase Control and Optimal Deposition Temperature

Thermoelectric thin films are vital for efficient energy conversion and thermal management. XRD analysis reveals that Cu₁.₈Se films exhibit a mixed α-phase when deposited at room temperature, 100°C, and 300°C, but transition to a pure β-phase at 200°C. The formation of the pure β-Cu₁.₈Se phase at 200°C significantly improves the crystallinity of the films. Increased annealing temperatures lead to greater surface roughness and grain size as observed by AFM and FESEM. Electrical conductivity decreases with higher measurement temperatures, reflecting degenerate semiconductor behavior due to Cu vacancies. The sample deposited at 200°C, exhibiting the pure β-phase, achieves the highest power factor of 5456 μWm⁻1K⁻2 and improved Seebeck coefficient, underscoring the importance of phase purity and controlled surface roughness for optimal thermoelectric performance. Keywodsannealing temperature; Surface Roughness; β-Cu1.8Se thin films; Thermoelectric

Low-temperature thermopower and phonon-drag effect in the quasi-one-dimensional cobaltate Ba3Co2O6(CO3)0.7

The quasi-one-dimensional cobaltate Ba3Co2O6(CO3)0.7 exhibits a high thermoelectric performance characterized by the large thermopower and high electrical conductivity above room temperature, while the low-temperature transport properties have been less investigated so far. Here, we systematically measure the thermopower of single-crystalline Ba3Co2O6(CO3)0.7 samples at low temperatures. The temperature dependence of the thermopower near room temperature is similar to that of other thermoelectric cobaltates, such as layered cobaltates, but exhibits a sample-dependent prominent peak structure near T = 40 K. We evaluate the sample dependence of the carrier density and the mobility and find that the saturation effect of phonon drag is essential for the observed peak structure in the thermopower. The enhanced thermopower utilizing a phonon-drag effect in the present material may be crucial for low-temperature thermoelectrics.

Revealing the improved thermoelectric performances of (BiSb)2Te3 alloy through rapid solidification of cold-water assisted water atomization approach

Revealing the improved thermoelectric performances of (BiSb)2Te3 alloy through rapid solidification of cold-water assisted water atomization approach

ZnO/Organic superlattice with phase composite structure for enhanced thermoelectric performance at low temperature

Semiconducting metal oxides, such as zinc oxide (ZnO), are gaining recognition for thermoelectric applications due to their temperature stability, availability, eco-friendliness, and cost-effectiveness. However, ZnO faces challenges in achieving high ZT value due to its low carrier concentration and high thermal conductivity. Traditional methods, like doping and defect engineering, have shown limited success in overcoming these challenges. In this study, we introduce a unique superlattice structure with a phase-composite composition that significantly decreases thermal conductivity through enhanced phonon scattering while maintaining the power factor by inducing new resonant conducting states near the mobility edge. By optimizing nanolayer thickness and doping concentration, we achieved a remarkable power factor of 14.6 μW cm−1 K−2 and reduced thermal conductivity to ∼1.97 W m−1 K−1 at room temperature in samples with 6 nm-thick ZnO nanolayers fabricated at 100 °C. This leads to a ZT value of ∼0.22 at 300 K, the highest among metal oxide thermoelectric materials at low temperatures, which further increases to ∼0.55 at 510 K. These findings demonstrate the potential of hybrid superlattices for efficient low-temperature thermoelectric applications.

High Performance and Colorful Polymer Thermoelectrics with Imprinted Porous Film.

The rapid development of the Internet of Things and wearable electronics has generated growing interest in creating high-performance and visually striking polymer thermoelectric (TE) devices. However, existing polymer TE materials have yet to fully meet these diverse demands. In this study, imprinted porous polymer films are introduced that exhibit both high TE performance and a spectrum of structural colors. The porous architecture not only preserves excellent charge transport properties but also significantly enhances phonon-like scattering, resulting in a more than 50% reduction in thermal conductivity for the PDPPSe-12 film. This leads to a 170% increase in the figure of merit (ZT), achieving a peak value of 0.52 at 363K. Furthermore, the highly ordered porous structure imparts the PDPPSe-12 films with both a wide range of structural colors and remarkable stretchability, making them ideal for wearable TE generators. This approach is widely applicable to various polymeric systems, offering a novel strategy for advancing state-of-the-art plastic TE materials through microstructural engineering.

Enhancing the Thermoelectric Performance of n-Type Mg3.2Sb1.5Bi0.5 by Reducing Lattice Thermal Conductivity through the Incorporation of Chlorine-Containing Compounds.

Mg3Sb2-based thermoelectric materials are characterized by their economic efficiency, nontoxicity, and environmental friendliness and represent a highly promising and eco-friendly functional material for midtemperature applications. To achieve a higher thermoelectric performance, we introduced two compounds, LaCl3 and CeCl3, into Mg3.2Sb1.5Bi0.5 under the guidance of first-principles calculations. The Mg3.2Sb1.5Bi0.5 + 0.03CeCl3 sample reached a maximum ZT value of approximately 1.6 at 723 K. The calculations indicate that two n-type dopants, LaCl3 and CeCl3, can adequately improve the band structure of Mg3Sb2, and the introduction of Cl atoms will also lead to lattice distortion and reduce the lattice thermal conductivity (κL). Experimental results demonstrate that the introduction of Cl atoms efficiently reduces the thermal conductivity while improving the electrical transport properties. Specifically, the Mg3.2Sb1.5Bi0.5 + 0.03CeCl3 sample achieved an exceptionally low κL of 0.3 W m-1 K-1 at 723 K, thereby validating the effectiveness of LaCl3 and CeCl3 doping. This work provides valuable insights into achieving thermoelectric decoupling in Mg3Sb2-based thermoelectric materials.

Optimizing Room‐Temperature Thermoelectric and Magnetocaloric Performance via Constructing Multi‐Scale Interfacial Phases in LaFeSi/BiSbTe Thermo‐Electro‐Magnetic Refrigeration Materials

AbstractFabricating a thermo‐electro‐magnetic material that exhibits simultaneously excellent magnetocaloric (MC) and thermoelectric (TE) performance is challenging since the interfacial reaction causes severe deterioration of MC and TE performance. In this work, a construction of multi‐scale interfaces in LaFe10.4Co0.8Si1.8/Bi0.5Sb1.5Te3 (LFS/BST) composites is realized by adopting a low‐temperature high‐pressure sintering strategy. It is revealed in the atomic‐scale that the interfacial reaction between LFS and BST leads to the formation of (Fe,Co)(Sb,Te)2 micro‐grains and LaTe2 nano‐grains, and the latter form low‐mismatch phase boundaries with LFS matrix. Benefiting from the multi‐scale interfacial phases, excellent MC performance of LFS is preserved alongside a minor impact on TE properties, e.g., a peak zT of 1.04 and a small decrease of 3.0% in relative cooling power are achieved in the 2%LFS/BST composite. Compared with other thermo‐electro‐magnetic materials, a good trade‐off between MC and TE performance is realized in LFS/BST composites with simultaneously high MC and TE performance. The 20%LFS/BST composite exhibits a room‐temperature zT of 0.46 with large maximum magnetic entropy change and relative cooling power of 0.81 J kg−1 K−1 and 44.83 J kg−1, respectively. This work provides an effective material design for developing the all‐solid‐state MC/TE hybrid refrigeration technique.