Semiclassical Boltzmann Transport Theory Research Articles

Comparative analysis of electronic and thermoelectric properties of strained and unstrained IrX3 (X=P, As) skutterudite materials

Abstract The electronic and thermoelectric properties of unfilled IrP3 and IrAs3 skutterudites materials under hydrostatic pressures are investigated using density functional theory (DFT) combined with semi-classical Boltzmann transport theory. Calculations of the elastic properties and phonon frequencies for both strained and unstrained materials demonstrate that they are mechanically and dynamically stable, with ductility varying based on the applied pressure. For pressures ranging from 0 to 30 GPa, the band structure calculations with the GGA+TB-mBJ approximation reveal that the band gap varies from 0.400 to 0.144 eV for IrP3 and from 0.341 to 0.515 eV for IrAs3. At 0 GPa, IrAs3 exhibits a direct band gap, whereas IrP3 has an indirect band gap. As pressure increases, IrAs3 undergoes a transition from a direct to an indirect band gap above 10 GPa, while IrP3 maintains its indirect band gap characteristic throughout the pressure range. 
The thermoelectric properties, at various pressures and temperatures between 300 and 1200 K, are also computed. These properties include the Seebeck coefficient, electrical conductivity, thermal conductivity (both electronic and lattice contributions), and relaxation time. The ideal conditions for efficient thermoelectric properties in IrAs3 are achieved at 30 GPa and 1200 K, with an optimal n-type doping concentration of 56×1019 cm-3, resulting in a ZT of 0.68. For IrP3, a ZT of approximately 0.46 is obtained at 600 K and 5 GPa, with a p-type doping concentration of 6.0×1018 cm-3.
The present study provides valuable insights into the behavior of skutterudite materials under strain, offering pathways for enhancing their performance in practical applications.

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.

Enhancing Thermoelectric Performance of Mg3Sb2 Through Substitutional Doping: Sustainable Energy Solutions via First-Principles Calculations

Mg3Sb2-based materials, part of the Zintl compound family, are known for their low thermal conductivity but face challenges in thermoelectric applications due to their low energy conversion efficiency. This study addressed these limitations through first-principles calculations using the CASTEP module in Materials Studio 8.0, aiming to enhance the thermoelectric performance of Mg3Sb2 via strategic doping. Density functional theory (DFT) calculations were performed to analyze electronic properties, including band structure and density of states (D.O.S.), providing insights into the influence of various dopants. The semiclassical Boltzmann transport theory, implemented in BoltzTrap (version 1.2.5), was used to evaluate key thermoelectric properties such as the Seebeck coefficient, electrical conductivity, electronic thermal conductivity, and electronic figure of merit (eZT). The results indicate that doping significantly improved the thermoelectric properties of Mg3Sb2, facilitating a transition from p-type to n-type behavior. Bi doping reduced the band gap from 0.401 eV to 0.144 eV, increasing carrier concentration and mobility, resulting in an electrical conductivity of 1.66 × 106 S/m and an eZT of 0.757. Ge doping increased the Seebeck coefficient to −392.1 μV/K at 300 K and reduced the band gap to 0.09 eV, achieving an electronic ZT of 0.859 with low thermal conductivity (11 W/mK). Si doping enhanced stability and achieved an electrical conductivity of 1.627 × 106 S/m with an electronic thermal conductivity of 11.3 W/mK, improving thermoelectric performance. These findings established the potential of doped Mg3Sb2 as a highly efficient thermoelectric material, paving the way for future research and applications in sustainable energy solutions.

Ab-initio prediction of gigantic anomalous Nernst effect in ferromagnetic monolayer transition metal trihalides

The anomalous Hall conductivity of all transition metal trihalides was explored using first-principles calculations. Employing the Fukui-Hatsugai-Suzuki method, we found that ferromagnetic monolayersXBr3(X= Pd, Pt) possessed the quantized anomalous Hall conductivity (QAHC) with and without carrier doping. Due to unique QAHC, their transverse thermoelectric properties ofXBr3(X= Pd, Pt) were investigated. Employing the semi-classical Boltzmann transport theory, the transverse thermoelectric coefficient of each monolayer was analyzed. Anomalous Nernst coefficients (ANCs) of theXBr3monolayers were prominent both at and near the Fermi level. Under an assumed relaxation time of 10 fs, the maximum ANCs for the PdBr3(PtBr3) monolayer reached -54.1 (-23.3)µV K-1atT=300 K upon doping with 1.21 × 1014(5.64 × 1013) holes cm-2. The large ANCs of theXBr3monolayers were attributed to the opening of a narrow bandgap generated by spin-orbit coupling both at and near the Fermi level, which led to a large Seebeck-induced charge current and large anomalous Nernst conductivity. These results suggest that ferromagneticXBr3monolayers have significant potential for application in thermoelectric devices.

Optical and thermoelectric properties of layer structured Ba2XS4 (X = Zr, Hf) for energy harvesting applications

The main objective of this research is to provide a comprehensive insight into the optical and thermoelectric properties of layer structured Ba2XS4(X = Zr, Hf) for energy harvesting applications using Density Functional Theory (DFT) and semiclassical Boltzmann transport theory. There is a good match between the computed lattice parameters and the available experimental data. Both compounds are thermodynamically and mechanically stable and they are soft, ductile, machinable, and elastically anisotropic. The indirect band gaps are found to be 1.03 eV for Ba2ZrS4 and 1.48 eV for Ba2HfS4. Both compounds possess a mixture of ionic and covalent bonding confirmed by charge density distribution and Mulliken bond population analysis. The maximum absorption is in the ultraviolet regions (∼13.6eV) of light spectra. The total thermal conductivity increases with temperature due to increasing trend of electronic thermal conductivity. The total thermal conductivity at 700 K along c-axis is 4.6 (6.1 W/mK) for Ba2ZrS4 (Ba2HfS4). For p-type Ba2ZrS4 (Ba2HfS4), power factor (PF) is about 7 (5.7) mW/mK2, whereas for n-type it is about 4 (3.9) mW/mK2 at 700 K along c-axis. The power factors of the studied compounds are much higher than those of the reported GeTe and SnSe which would create great interest for further study. The predicted ZT values at 700 K for p-type Ba2ZrS4 and Ba2HfS4 are 0.7 and 0.6, respectively. These values may further be improved through reduction of thermal conductivity and tuning ductility employing known suitable strategies such as alloying and nano-structuring. Finally, Ba2ZrS4 and Ba2HfS4 can be considered new eco-friendly alternatives to previously studied toxic lead-based thermoelectric materials. Their unique advantages of high thermodynamic stability, non-toxic nature and high performance make them strong candidate for sustainable energy solutions.

Atomistic spin dynamics simulations of magnonic spin Seebeck and spin Nernst effects in altermagnets

Magnon band structures in altermagnets are characterized by an energy splitting of modes with opposite chirality, even in the absence of applied external fields and relativistic effects, because of an anisotropy in the Heisenberg exchange interactions. We perform quantitative atomistic spin dynamics simulations based on electronic structure calculations on rutile RuO2, a prototypical “d-wave” altermagnet, to study magnon currents generated by thermal gradients. We report substantial spin Seebeck and spin Nernst effects, i.e., longitudinal or transverse spin currents, depending on the propagation direction of the magnons with respect to the crystal, together with a finite spin accumulation associated with nonlinearities in the temperature profile. Our findings are consistent with the altermagnetic spin-group symmetry, as well as predictions from linear spin-wave theory and semiclassical Boltzmann transport theory. Published by the American Physical Society 2024

Influence behavior and mechanism of double-layer Gr stacking configuration on mechanical strength and thermoelectric transport properties of Cu/Gr composites

The mechanical strength, electrical conductivity, and thermal conductivity of Cu/graphene (Gr) composites with Cu (111)/double-layer Gr/Cu (111) structure were investigated by using density functional theory and semi-classical Boltzmann transport theory. The results indicate that, the chemical bonds were generated between the two layers of Gr film, and the maximum charge densities of Gr-Top stacking configuration and Gr-Hollow stacking configuration are 0.104 and 0.118 e/Å3, respectively. Gr-Hollow stacking configuration has the larger mechanical strength and plasticity than Gr-Top stacking configuration. Although the covalent characteristic for the two stacking configurations is identical, the ionic characteristic of Gr-Top stacking configuration is stronger than Gr-Hollow stacking configuration. Therefore, the electron localization of Gr-Top stacking configuration is much stronger, leading to the smaller number of free electrons. The electrical conductivity and thermal conductivity of Gr-Hollow stacking configuration are 2.55 times and 1.63 times those of Gr-Top stacking configuration was achieved. Moreover, as the external longitudinal strain from 0 % to 15 % applied on Cu (111)/double-layer Gr/Cu (111) structure, the thermoelectric transport properties of Gr-Hollow stacking configuration are greater than Gr-Top stacking configuration, while as the strain are 20 % and 25 %, Gr-Top stacking configuration has the larger electric conductivity and thermal conductivity instead.

General Theory for Longitudinal Nonreciprocal Charge Transport.

The longitudinal nonreciprocal charge transport (NCT) in crystalline materials is a highly nontrivial phenomenon, motivating the design of next generation two-terminal rectification devices (e.g., semiconductor diodes beyond PN junctions). The practical application of such devices is built upon crystalline materials whose longitudinal NCT occurs at room temperature and under low magnetic field. However, materials of this type are rather rare and elusive, and theory guiding the discovery of these materials is lacking. Here, we develop such a theory within the framework of semiclassical Boltzmann transport theory. By symmetry analysis, we classify the complete 122magnetic point groups with respect to the longitudinal NCT phenomenon. The symmetry-adapted Hamiltonian analysis further uncovers a previously overlooked mechanism for this phenomenon. Our theory guides the first-principles prediction of longitudinal NCT in multiferroic ϵ-Fe_{2}O_{3} semiconductor that possibly occurs at room temperature, without the application of external magnetic field. These findings advance our fundamental understandings of longitudinal NCT in crystalline materials, and aid the corresponding materials discoveries.

A theoretical investigation on the structure stability, electronic structures, optical properties, and transport properties of Zintl compounds CsZn4P3 and CsZn4As3

The present study investigates the structure stability, electronic structures, and optical properties of Zintl compounds CsZn4P3 and CsZn4As3 by first-principles calculations. An assessment of the phonon dispersion curves and elastic constants indicate both dynamic and mechanical stability for the both compounds. By employing the HSE06 hybrid functional, both compounds display direct bandgap with widths of 0.93 eV for CsZn4P3 and 0.66 eV for CsZn4As3. Furthermore, an analysis of the dielectric constant, refractive index, extinction coefficient, and energy loss as functions of photon energy is conducted to study the optical properties. Based on the semi-classical Boltzmann transport theory and the Slack's equation, a large Seebeck coefficient and minimum lattice thermal conductivity are obtained for CsZn4As3, which result in a figure of merit value of 0.79 at 700 K. These findings underscore the potential of CsZn4As3 as a promising candidate for future research and development in the realm of thermoelectric materials.

Strain aided drastic reduction in lattice thermal conductivity and improved thermoelectric properties in Janus MXenes

Surface and strain engineering are among the cheaper ways to modulate structure property relations in materials. Due to their compositional flexibilities, MXenes, the family of two-dimensional materials, provide enough opportunity for surface engineering. In this work, we have explored the possibility of improving thermoelectric efficiency of MXenes through these routes. The Janus MXenes obtained by modifications of the transition metal constituents and the functional groups passivating their surfaces are considered as surface engineered materials on which bi-axial strain is applied in a systematic way. We find that in the three Janus compounds Zr2COS, ZrHfCO2and ZrHfCOS, tensile strain modifies the electronic and lattice thermoelectric parameters such that the thermoelectric efficiency can be maximised. A remarkable reduction in the lattice thermal conductivity due to increased anharmonicity and elevation in Seebeck coefficient are obtained by application of moderate tensile strain. With the help of first-principles electronic structure method and semi-classical Boltzmann transport theory we analyse the interplay of structural parameters, electronic and dynamical properties to understand the effects of strain and surface modifications on thermoelectric properties of these systems. Our detailed calculations and in depth analysis lead not only to the microscopic understanding of the influences of surface and strain engineering in these three systems, but also provide enough insights for adopting this approach and improve thermoelectric efficiencies in similar systems.

Structural, electronic, magnetic, and thermoelectric properties of half Heusler alloys ZrCo1-XFeXSb (X = 0, 0.25, 0.5, 0.75, 1): A DFT study

The structural, electronic, magnetic, and thermoelectric properties of half-Heusler alloys ZrCo1-XFeXSb (X = 0, 0.25, 0.5, 0.75, 1) are investigated using the density functional theory. It is evident that ZrCoSbis a non-magnetic semiconductor. This study investigates the influence of substituting Fe for Co on the electronic structure and magnetic characteristics of ZrCoSb. The alloys transform into half-metallic ferromagnets as Fe substitutes Co. The indirect band gap of the ZrCo1-XFeXSb alloys decreases with increasing Fe content. The phonon dispersion curve is studied to determine the structural stability. The calculated values for the elastic constant for each composition satisfy the criteria for mechanical stability. To analyse its thermoelectric properties, the semi-classical Boltzmann transport theory is used to determine the Seebeck coefficients, electrical and thermal conductivities, and power factor as a function of temperature.

A comprehensive DFT analysis of the physical, optoelectronic and thermoelectric attributes of Ba2lnNbO6 double perovskites for eco-friendly technologies

Within the framework of density functional theory (DFT), as executed in WIEN2k as well as semi-classical Boltzmann transport theory, we reported structural, electronic, elastic, optical, thermoelectric, and thermodynamic properties of the double perovskite compound Ba2InNbO6. To employ the exchange–correlation potential, local density approximation (LDA), the generalized gradient approximation (GGA) with Perdew, Burke and Ernzerhof (PBE) and the modified Becke–Johnson (mBJ) potential is considered. The elastic constants are calculated to check the mechanical stability. The electronic calculations show semiconducting nature with a wide band-gap (3.63 eV) for Ba2InNbO6. The optical properties such as complex dielectric constant ε(ω), refractive index n(ω), reflectivity R(ω), absorption coefficient α(ω), optical conductivity σ(ω) and energy loss function L(ω) described with the incidence frequency. The absorption spectrum shows the behaviour of common semiconductors. The Seebeck coefficient (S) as well as electrical conductivity (σ/τ) also demonstrates the semiconducting nature of the studied compounds by holes having highest particles. The PF was 1.85 × 1012 W K−2 m−1 s−1 at 1200 K and thermodynamic studies, the heat capacity as well as Gruneisen parameter were guessed. Based on obtained results we can ensure that the double perovskite compound Ba2InNbO6 is well suitable for optical and thermoelectric applications.

Band Degeneracy and Anisotropy Enhances Thermoelectric Performance from Sb2Si2Te6 to Sc2Si2Te6.

The complex interrelationships among thermoelectric parameters mean that a priori design of high-performing materials is difficult. However, band engineering can allow the power factor to be optimized through enhancement of the Seebeck coefficient. Herein, using layered Sb2Si2Te6 and Sc2Si2Te6 as model systems, we comprehensively investigate and compare their thermoelectric properties by employing density functional theory combined with semiclassical Boltzmann transport theory. Our simulations reveal that Sb2Si2Te6 exhibits superior electrical conductivity compared to Sc2Si2Te6 due to lower scattering rates and more pronounced band dispersion. Remarkably, despite Sb2Si2Te6 exhibiting a lower lattice thermal conductivity and superior electrical conductivity, Sc2Si2Te6 is predicted to achieve an extraordinary dimensionless figure of merit (ZT) of 3.51 at 1000 K, which significantly surpasses the predicted maximum ZT of 2.76 for Sb2Si2Te6 at 900 K. We find the origin of this behavior to be a combined increase in band (valley) degeneracy and anisotropy upon switching the conduction band orbital character from Sb p to Sc d, yielding a significantly improved Seebeck coefficient. This work suggests that enhancing band degeneracy and anisotropy (complexity) through compositional variation is an effective strategy for improving the thermoelectric performance of layered materials.

Enhanced Thermoelectric Performance of Nanostructured 2D Tin Telluride.

A lot of experimental studies are conducted on theoretically predicted thermoelectric 2D materials. Such materials can pave the way for charging ultra-thin electronic devices, self-charging wearable devices, and medical implants. This study systematically explores the thermoelectric attributes of bulk and 2D nanostructured Tin Telluride (SnTe), employing experimental investigations and theoretical analyses based on semiclassical Boltzmann transport theory. The bulk SnTe is synthesized through flame melting, while the 2D SnTe is produced via liquid phase exfoliation. The comprehensive assessment of thermoelectric properties integrated experimental measurements utilizing a Physical Property Measurement System and theoretical calculations from the BoltzTraP code. Experimental thermoelectric studies show a high ZT of 0.17 for 2D SnTe when compared to bulk (0.005) at room temperature. This rise in ZT is due to the high Seebeck coefficient and low thermal conductivity of nanostructured 2D SnTe. Density functional theory (DFT) studies reveal the contribution of the density of states (DOS) and energy bandgap in enhancing the Seebeck coefficient and lowering thermal conductivity by interface scattering.

The electronic structures, half-metallic ferromagnetism, optical, and thermoelectric responses of the Co-doped Au2S chalcogenide compound

The structural, electronic, magnetic, optical, and thermoelectric properties of diluted magnetic semiconductors (DMS) based on the chalcogenide compounds Au3CoS2, Au2Co2S2, and AuCo3S2 have been investigated using all-electron first-principles calculations. We have used the GGA-PBEsol and the around mean-field (AMF) correction scheme (GGA-PBEsol + U) for the exchange-correlation energies. Firstly, we calculated the equilibrium ground state of properties. Afterward, we evaluated the magneto-electronic properties using the GGA-PBEsol and GGA-PBEsol + U approaches. The computed spin-polarized band structures and density of states revealed the half-metallic ferromagnetic behavior for the studied compounds from both approaches. The half-metallicity is mainly due to the p-d hybridization of S and Co atoms. We also estimated the Curie temperatures using the mean-field approximation, and the results exceeded the ambient temperature. The real and imaginary components of the dielectric function, as well as the refractive index and reflectivity, were calculated up to 13.0 eV for both spin directions to explore the optical responses of AuCo3S2, Au2Co2S2, and Au3CoS2 compounds. The thermoelectric responses have also been reported for the spin-up orientation using the semi-classical Boltzmann transport theory and indicate that the half-metallic behavior is maintained at high temperatures. Finally, both the importance and potential applications of the studied compounds are discussed in this study.

Strain-tunable electronic structure, optical and thermoelectric properties of BAs

Strain engineering stands as a reliable method for tailoring the physicochemical properties of materials to achieve desired performance. However, the effects of strain on the physicochemical properties of BAs remain unclear, impeding the comprehensive understanding of its practical performance. Here, employing first-principles calculations coupled with semiclassical Boltzmann transport theory, we investigate the dynamic stability, mechanical stability, electronic structure, and thermoelectric properties of cubic boron arsenide (BAs) under various strains. The results demonstrate that BAs maintains excellent stability throughout the triaxial strain range. The electronic structure of BAs is less affected by strain. Young’s modulus and Poisson’s ratio show a corresponding linear increase when the compression strain increases. The optical absorption coefficient in the visible region of BAs under tensile strain showed an overall increasing trend, and the optical absorption coefficient in the visible wavelength region of BAs under 5% tensile strain was as high as 2 × 105 cm−1. The thermoelectric properties of BAs under tensile strain have been improved, and the ZT value of BAs under 5% tensile strain at 1500 K has been increased to 0.6. The research findings address the gaps in understanding the properties of BAs under strain and provide theoretical support for its applications in the fields of thermoelectrics and optoelectronics.

Defect-induced modifications in electronic and thermoelectric properties of pentagonal PdX2 (X = Se, S) monolayers

The point defects induced in crystalline solids during the growth process unintentionally or doped intentionally after the growth process significantly modify their properties. The intentionally controlled doping of point defects in crystalline solids has been widely used to tune their properties. In this paper, we investigate the effect of vacancy and substitutional point defects on the electronic and thermoelectric properties of pentagonal PdX2 (X = Se, S) monolayers using the density functional theory (DFT) and semi-classical Boltzmann transport theory. We find that the point defects in pentagonal PdX2 (X = Se, S) monolayers modify their electronic structures. The contributions of d orbitals of Pd atoms and p orbitals of Se/S atoms are significantly affected due to the presence of point defects in the lattice. The defect states are appeared within the band gap region which effectively reduces the band gap of the monolayer. These defect states could be helpful in tuning the electrical and optical properties of the monolayer. The defect states appear within the band gaps of defective monolayer structures which effectively modifies the electronic properties of these monolayer structures. The transport calculations show that the presence of the point defects in the lattice reduces the thermoelectric performance of these PdX2 monolayers. Both the Seebeck coefficient and electrical conductivity show deteriorated behaviour under the influence of point defects in the lattice. Thus, the influence of these defects must be carefully taken into account while fabricating these materials for practical applications.

Structural characteristics, mechanical properties, electronic behavior, and lattice thermal conductivities for novel LaX phases (X = P, As, Sb)

Rare-earth-metal monopnictides have rich high-pressure structures, magnetism, and topological properties, but there is still relatively little research related to them, especially in recent years. We here predict a new group of LaX (X = P, As, Sb) phases (HR-type) by means of the particle swarm optimization method. Their stabilities can be verified by dynamic, thermodynamic, and mechanical calculations. By utilizing the density functional and semiclassical Boltzmann transport theory, we investigate their mechanic, electronic, and thermal transport properties. These HR-type LaX are rather soft with lower than 6 GPa of Vickers hardness, and exhibit the obvious mechanical anisotropy. These HR-type LaX also exhibit amazing topological properties, owning a mostly flat surface band between two bulk Dirac cones. Based on the calculations of gaps in energy dispersion planes and Z2 invariants, we prove that these HR-type LaX should be the nodal-line semimetals. We compute their lattice thermal conductivities, and find that HR-type LaAs own the largest lattice thermal conductivity of 6.34 (22.34) W/mK along x (y) direction at 300 K. This mean free path of the pertinent heat-carrying phonons in the HR-type LaX are also predicted. Our research might offer new perspectives on the various allotropes of rare-earth-metal monopnictides.

Ab initio study of the physical characteristics of CsPb1-xMoxBr3 perovskites

Doped CsPbBr3 perovskites are recently in great interest because of their potential in tandem solar cell applications. In this study, the structural, electronic, magnetic, thermoelectric, and optical properties of CsPb1-xMoxBr3 (x=0, 0.25, 0.5, 0.75) cubic phase perovskites are investigated by using density functional theory and semi-classical Boltzmann transport theory. The trend of the lattice parameters decreases with increasing the Mo concentration, which corresponds to Vegard's law. The stability of all studied compounds is proved by estimating the cohesive energy and phonons frequency modes at Γ points. There is no certain trend in band gap variation, but the minimum band gap (1.386 eV PBE or 1.872 eV mBJ) has occurred at x=0.5. The values of the absorption coefficient are slightly significant near the infrared region for Mo-doped compounds and this could make them promising candidates in infrared applications. Furthermore, the spin-polarized DOS revealed their ferromagnetic half-metal behavior. The figure of merit at spin-up at room temperature is close to 1.0 for doped compounds.

GaInX3 (X = S, Se, Te): Ultra-low thermal conductivity and excellent thermoelectric performance

Abstract Seeking intrinsically low thermal conductivity materials is a viable strategy in the pursuit of high-performance thermoelectric materials. Here, by using first-principles calculations and semiclassical Boltzmann transport theory, we systemically investigate the carrier transport and thermoelectric properties of monolayer Janus GaInX3 (X = S; Se; Te). It is found that the lattice thermal conductivities can reach values as low as 3.07 Wm−1K−1, 1.16 Wm−1K−1 and 0.57 Wm−1K−1 for GaInS3, GaInSe3, and GaInTe3, respectively, at room temperature. These notably low thermal conductivity is attributed to strong acoustic-optical phonon coupling caused by the presence of low-frequency optical phonons in GaInX3 materials. Furthermore, by integrating the characteristics of electronic and thermal transport, the dimensionless figure of merit ZT can reach maximum values of 0.95, 2.37, and 3.00 for GaInS3, GaInSe3, and GaInTe3, respectively. Our results suggest monolayer Janus GaInX3 (X = S; Se; Te) are promising candidates for thermoelectric and heat management applications.