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Cu3SbSe4, a copper-based sulfide free of rare earth elements, has received extensive attention in thermoelectric materials. However, its low carrier concentration restricts its widespread application. In this study, a microwave-assisted solution synthesis method was used to produce samples of Cu3SbSe4, which enabled the formation of CuSe in situ and increased the yield. Through the use of first-principles calculations, structural analysis, and performance evaluation, it was found that CuSe can enhance the carrier concentration and that induced nano-defects have a positive effect on reducing the lattice thermal conductivity. Moreover, doping with Sn decreases the band gap of the system and moves the Fermi level into the valence band, increasing the carrier concentration to 1.15 × 10−20 cm−3. Finally, the zT value of the Cu3Sb0.98Sn0.02Se4 sample was achieved at 1.05 at 623 K when the theoretical yield of a single synthesis was 10 mmol.

The previous works commonly adjust the carrier concentration through acceptor doping, but at the same time, the decrease of the Seebeck coefficient limits the further improvement of electrical properties in Cu3SbSe4-based materials. In this work, a microwave-assisted hydrothermal synthesis method was used to synthesize Cu3SbSe4/TiO2 hollow microspheres. Part of TiO2 participates in the reaction, replaces the Sb site of Cu3SbSe4 to form holes, and the rest is dispersed in the matrix in the form of the second phase. The first-principles calculations reveal that the doping of Ti significantly changes the band structure and phonon spectrum, thereby regulating carrier concentration while increasing phonon scattering. In addition, experimental results show that the energy filtering effect generated by the extra-mixed TiO2 nano particles, which suppresses the decrease of Seebeck coefficient by acceptor doping. Consequently, the highest average power factor 897.5 μW m−1 K−2 and the zT peak value of 0.70 can be obtained in Cu3SbSe4/6%TiO2 sample at 298–623 K. This work provides a new sight to improve the thermoelectric properties in Cu3SbSe4 through carrier concentration regulation and nano-phase composition.

The p-type Te-free Cu3SbSe4 with famatinite structure is a potential candidate for thermoelectric materials due to the low cost and eco-friendly constituent elements. However, its strong bipolar effect and high lattice thermal conductivity (κlat) are the main challenges for its performance enhancement. Herein, we report a new strategy to enhance its figure of merit zT ∼0.86 at 673 K for Cu3Sb0.95Fe0.05Se2.8S1.2 via band structure tuning and hierarchical architecture. Firstly, S substituted Se atoms in lattice can widen the band gap to alleviate the bipolar effect. Secondly, Fe doping in Sb site significantly increases the density of states, thus increasing the carrier effective mass, and obtaining a remarkably high Seebeck coefficient of ∼560 μV/K at 300 K. Moreover, the induced hierarchical architecture defects resulting in a minimum κlat of ∼0.48 W·m−1·K−1 at 673 K. Consequently, the improved Seebeck coefficient combined with low thermal conductivity leads to an enhanced zT.

Cu3SbSe4 is a potential p-type thermoelectric material, distinguished by its earth-abundant, inexpensive, innocuous, and environmentally friendly components. Nonetheless, the thermoelectric performance is poor and remains subpar. Herein, the electrical and thermal transport properties of Cu3SbSe4 were synergistically optimized by S alloying. Firstly, S alloying widened the band gap, effectively alleviating the bipolar effect. Additionally, the substitution of S in the lattice significantly increased the carrier effective mass, leading to a large Seebeck coefficient of ~730 μVK−1. Moreover, S alloying yielded point defect and Umklapp scattering to significantly depress the lattice thermal conductivity, and thus brought about an ultralow κlat ~0.50 Wm−1K−1 at 673 K in the solid solution. Consequently, multiple effects induced by S alloying enhanced the thermoelectric performance of the Cu3SbSe4-Cu3SbS4 solid solution, resulting in a maximum ZT value of ~0.72 at 673 K for the Cu3SbSe2.8S1.2 sample, which was ~44% higher than that of pristine Cu3SbSe4. This work offers direction on improving the comprehensive TE in solid solutions via elemental alloying.

Cu3SbSe4 is a potential p-type thermoelectric material, distinguished by its earth-abundant, inexpensive, innocuous, and environmentally friendly components. Nonetheless, the thermoelectric performance is poor and remains subpar. Herein, the electrical and thermal transport properties of Cu3SbSe4 were synergistically optimized by S alloying. Firstly, S alloying widened the band gap, effectively alleviating the bipolar effect. Additionally, the substitution of S in the lattice significantly increased the carrier effective mass, leading to a large Seebeck coefficient of ~730 μVK−1. Moreover, S alloying yielded point defect and Umklapp scattering to significantly depress the lattice thermal conductivity, and thus brought about an ultralow κlat ~0.50 Wm−1K−1 at 673 K in the solid solution. Consequently, multiple effects induced by S alloying enhanced the thermoelectric performance of the Cu3SbSe4-Cu3SbS4 solid solution, resulting in a maximum ZT value of ~0.72 at 673 K for the Cu3SbSe2.8S1.2 sample, which was ~44% higher than that of pristine Cu3SbSe4. This work offers direction on improving the comprehensive TE in solid solutions via elemental alloying. [ABSTRACT FROM AUTHOR]

Cu 3 SbSe 4 is a promising Te-free p-type thermoelectric material, characterized by earth-abundant, low-cost, and environmentally friendly constituents. Nonetheless, its thermoelectric performance is poor due to its extremely low electrical conductivity (deriving from the low carrier concentration) and high lattice thermal conductivity. Herein, we report a high-performance Cu 3 SbSe 4 -based material by compositing LaCl3 and introducing multiscale structure. The LaCl 3 -composted Cu 3 SbSe 4 forms heterojunctions that facilitate charge accumulation at the interfaces. The redistribution of electrons between the two materials increases the electrical conductivity without damaging the Seebeck coefficient, and thereby significantly improving the power factor to ∼1150 μWm−1K−2 for Cu 3 SbSe 4 -based bulk. Furthermore, the hierarchical architecture defects are induced by LaCl 3 compositing, yielding a minimum κ lat of ∼0.68 Wm−1K−1 at 673 K. As a consequence, a maximum ZT value of ∼0.90 at 673 K is achieved in the Cu 3 SbSe 4 +2 mol% LaCl 3 sample, representing an 80 % improvement compared to the pristine Cu 3 SbSe 4. [Display omitted] • A high-performance Cu 3 SbSe 4 -based material is obtained by compositing LaCl3 and introducing hierarchical architecture. • LaCl 3 compositing induce the formation of phase interfaces, thus synergistically increasing σ and suppressing κ lat. • Hierarchical architecture defects involving point defects, second phase, dislocations, grain boundaries and phase interfaces decrease κ lat. • LaCl 3 compositing boost Cu 3 SbSe 4 to an outstanding ZT value ∼0.90 at 673 K. [ABSTRACT FROM AUTHOR]

Developing cost‐effective and high‐performance thermoelectric (TE) materials to assemble efficient TE devices presents a multitude of challenges and opportunities. Cu3SbSe4 is a promising p‐type TE material based on relatively earth abundant elements. However, the challenge lies in its poor electrical conductivity. Herein, an efficient and scalable solution‐based approach is developed to synthesize high‐quality Cu3SbSe4 nanocrystals doped with Pb at the Sb site. After ligand displacement and annealing treatments, the dried powders are consolidated into dense pellets, and their TE properties are investigated. Pb doping effectively increases the charge carrier concentration, resulting in a significant increase in electrical conductivity, while the Seebeck coefficients remain consistently high. The calculated band structure shows that Pb doping induces band convergence, thereby increasing the effective mass. Furthermore, the large ionic radius of Pb2+ results in the generation of additional point and plane defects and interphases, dramatically enhancing phonon scattering, which significantly decreases the lattice thermal conductivity at high temperatures. Overall, a maximum figure of merit (zTmax) ≈ 0.85 at 653 K is obtained in Cu3Sb0.97Pb0.03Se4. This represents a 1.6‐fold increase compared to the undoped sample and exceeds most doped Cu3SbSe4‐based materials produced by solid‐state, demonstrating advantages of versatility and cost‐effectiveness using a solution‐based technology. [ABSTRACT FROM AUTHOR]

Developing cost‐effective and high‐performance thermoelectric (TE) materials to assemble efficient TE devices presents a multitude of challenges and opportunities. Cu3SbSe4 is a promising p‐type TE material based on relatively earth abundant elements. However, the challenge lies in its poor electrical conductivity. Herein, an efficient and scalable solution‐based approach is developed to synthesize high‐quality Cu3SbSe4 nanocrystals doped with Pb at the Sb site. After ligand displacement and annealing treatments, the dried powders are consolidated into dense pellets, and their TE properties are investigated. Pb doping effectively increases the charge carrier concentration, resulting in a significant increase in electrical conductivity, while the Seebeck coefficients remain consistently high. The calculated band structure shows that Pb doping induces band convergence, thereby increasing the effective mass. Furthermore, the large ionic radius of Pb2+ results in the generation of additional point and plane defects and interphases, dramatically enhancing phonon scattering, which significantly decreases the lattice thermal conductivity at high temperatures. Overall, a maximum figure of merit (zTmax) ≈ 0.85 at 653 K is obtained in Cu3Sb0.97Pb0.03Se4. This represents a 1.6‐fold increase compared to the undoped sample and exceeds most doped Cu3SbSe4‐based materials produced by solid‐state, demonstrating advantages of versatility and cost‐effectiveness using a solution‐based technology. [ABSTRACT FROM AUTHOR]

Cu3SbSe4, featuring its earth-abundant, cheap, nontoxic and environmentally friendly constituent elements, can be considered as a promising intermediate temperature thermoelectric (TE) material. Herein, a series of p-type Bi-doped Cu3Sb1−xBixSe4 (x = 0–0.04) samples were fabricated through melting and hot pressing process, and the effects of isovalent Bi-doping on their TE properties were comparatively investigated by experimental and computational methods. TEM analysis indicates that Bi-doped samples consist of Cu3SbSe4 and Cu2−xSe impurity phases, which is in good agreement with the results of XRD, SEM and XPS. For Bi-doped samples, the reduced electrical resistivity (ρ) caused by the optimized carrier concentrations and enhanced Seebeck coefficient derived from the densities of states near the Fermi level give rise to a high power factor of ~ 1000 µWm−1 K−2 at 673 K for the Cu3Sb0.985Bi0.015Se4 sample. Additionally, the multiscale defects of Cu3SbSe4-based materials involving point defects, nanoprecipitates, amorphous phases and grain boundaries can strongly scatter phonons to depress lattice thermal conductivity (κlat), resulting in a low κlat of ~ 0.53 Wm−1 K−1 and thermal conductivity (κtot) of ~ 0.62 Wm−1 K−1 at 673 K for the Cu3Sb0.98Bi0.02Se4 sample. As a consequence, a maximum ZT value ~ 0.95 at 673 K is obtained for the Cu3Sb0.985Bi0.015Se4 sample, which is ~ 1.9 times higher than that of pristine Cu3SbSe4. This work shows that isovalent heavy element doping is an effective strategy to optimize thermoelectric properties of copper-based chalcogenides. [ABSTRACT FROM AUTHOR]

The improvement of the thermoelectric performance of semiconducting chalcogenides is an important task. The principal challenge in this field is to tailor the thermoelectric properties, such as electrical conductivity, Seebeck coefficient, and thermal conductivity, to improve the figure of merit (ZT). Herein, we present an improvement in the thermoelectric properties of InIII-doped p-type Cu3SbSe4 thin films deposited by using a microwave-assisted technique. The deposited thin films were characterized for their optical, structural, morphological, compositional, and electrical transport properties to show the applicability of the materials in thermoelectric energy conversion. The improvement in ZT is achieved with InIII doping because of the enhancement in the charge carrier density of Cu3SbSe4 thin films. A maximum ZT of 0.183 was achieved for Cu3(Sb0.94In0.06)Se4 at 300 K. Our results show that this deposition strategy and doping process can provide an effective solution to fabricate Cu3SbSe4-based materials for thermoelectric applications. [ABSTRACT FROM AUTHOR]

Large-scale Sn and/or S doped Cu3Sb1−xSnxSe4−ySy (x = 0.02, 0.04, 0.06 and 0.10; y = 0, 0.5) nanoparticles were first prepared through a low-temperature co-precipitation route. The effects of Sn doping on the thermoelectric properties of the Cu3SbSe4-based materials were explored. Due to the improved power factor from optimizing the carrier concentration and the reduced lattice thermal conductivity from enhanced phonon scattering at the grain interfaces, the maximum thermoelectric figure of merit, ZTmax, obtained here reached 1.1 for the co-doped Cu3Sb0.94Sn0.06Se3.5S0.5 material, which is the largest value reported for Cu3SbSe4-based materials. [ABSTRACT FROM AUTHOR]

The research on thermoelectric (TE) materials has a long history. Holding the advantages of high elemental abundance, lead-free and easily tunable transport properties, copper-based diamond-like (CBDL) thermoelectric compounds have attracted extensive attention from the thermoelectric community. The CBDL compounds contain a large number of representative candidates for thermoelectric applications, such as CuInGa2, Cu2GeSe3, Cu3SbSe4, Cu12SbSe13, etc. In this study, the structure characteristics and TE performances of typical CBDLs were briefly summarized. Several common synthesis technologies and effective strategies to improve the thermoelectric performances of CBDL compounds were introduced. In addition, the latest developments in thermoelectric devices based on CBDL compounds were discussed. Further developments and prospects for exploring high-performance copper-based diamond-like thermoelectric materials and devices were also presented at the end. [ABSTRACT FROM AUTHOR]

The influence of Bi doping on the structural and thermoelectric properties of Cu2Se is presented in this work. Cu2−xBixSe (x = 0.00, 0.004, 0.008, 0.012) samples were prepared using conventional solid-state reaction techniques. According to room temperature XRD results, Cu2−xBixSe samples have a monoclinic crystal structure. Doping Bi to the Cu site acts as a donor, lowering the hole concentration, except for the sample with x = 0.004. The resistivity of the Cu2−xBixSe sample increases with an increase in Bi content. Seebeck coefficient data confirm that the holes are the charge carriers in Cu2−xBixSe samples. At 700 K, the Cu1.988Bi0.012Se sample has the highest power factor of 1474 μWm−1K−2, showing great potential in developing high-performance Cu2Se based thermoelectric materials. [ABSTRACT FROM AUTHOR]

Forming co-alloying solid solutions has long been considered as an effective strategy for improving thermoelectric performance. Herein, the dense Cu2−x(MnFeNi)xSe (x = 0–0.09) with intrinsically low thermal conductivity was prepared by a melting-ball milling-hot pressing process. The influences of nanostructure and compositional gradient on the microstructure and thermoelectric properties of Cu2Se were evaluated. It was found that the thermal conductivity decreased from 1.54 Wm−1K−1 to 0.64 Wm−1K−1 at 300 K via the phonon scattering mechanisms caused by atomic disorder and nano defects. The maximum zT value for the Cu1.91(MnFeNi)0.09Se sample was 1.08 at 750 K, which was about 27% higher than that of a pristine sample. [ABSTRACT FROM AUTHOR]

The ternary Cu3SbSe4 thermoelectric material with diamond-like structure exhibit good electrical properties in the middle-temperature region. Forming co-alloying solid solutions has long been considered as an effective strategy for decoupling electrical conductivity and Seebeck coefficient. In this study, the Cu3-xAgxSb1-yTeySe4 (x = 0–0.1; y = 0–0.05) materials were fabricated by melting-ball milling-hot pressing process. The influences of configurational entropy on the microstructure and thermoelectric properties of Cu3SbSe4 were evaluated. It was found that the electrical conductivity of Cu2.9Ag0.1Sb0.95Te0.05Se4 was about 200% higher than that of pure sample due to the slightly configurational entropy tuning. Moreover, multiscale free path phonons of Cu2.9Ag0.1Sb0.95Te0.05Se4 can be greatly scattered and the lattice thermal conductivity decreased from 3.0 to 2.1 Wm−1 K−1 at 300 K via lattice-distortion effect. The maximum zT value of 0.84 was obtained at 650 K for the Cu2.9Ag0.1Sb0.95Te0.05Se4 sample. These results displayed the multiple effects on thermoelectric transport during the formation of co-alloying solid solutions. [ABSTRACT FROM AUTHOR]

Cu 3 SbSe 4 -based materials have attracted much attention for thermoelectric power generation in the mid-temperature range due to their low cost, ecofriendliness, and abundant elements on the earth. However, the peak figure of merit ( ZT ) for the Cu 3 SbSe 4 -based system prepared by the fusion method is usually smaller than unity because of its high thermal conductivity. Here, we show that through a coprecipitation method combined with spark plasma sintering ultrafine-grained Cu 3 Sb 0.94 Sn 0.06 Se 4- y S y ( y = 0, 0.5) embedded with Cu 3 SbSe 3 nanoprecipitates can be prepared. Due to the ultralow thermal conductivity and enhanced Seebeck coefficient, a record-high ZT value of 1.32 is achieved for the sample Cu 3 Sb 0.94 Sn 0.06 Se 3.5 Se 0.5 . The ultralow thermal conductivity is attributed to the enhanced phonon scattering caused by the nanoprecipitates and fine grains of the samples, and the improved Seebeck coefficient originates from the enhancement of electronic density-of-state effective mass. Present results demonstrate that excellent thermoelectric performance can be realized in dual-substituted and fine-grained Cu 3 Sb 0.94 Sn 0.06 Se 4- y S y with nanoprecipitates.

(Ag,Sn) co-doped Cu3SbSe4 nanocrystals are obtained via a facile microwave-assisted solvothermal method, and their thermoelectric properties are investigated in the temperature range from 300 K to 623 K. Sn-doping on Sb sites dramatically increases the carrier concentration and thus the electrical conductivity, promoting the thermoelectric power factor. Further alloying with Ag on Cu sites strongly suppresses the lattice thermal conductivity close to the glass limit. Aside from point defect scattering, such reduction in lattice thermal conductivity largely relies on the formation of Cu2-xSe nanoinclusions, which serve as additional scattering centers for phonons. Overall, the sample with the nominal composition of Cu2.8Ag0.2Sb0.95Sn0.05Se4 reaches a minimum lattice thermal conductivity of 0.27 W m-1 K-1 and a maximum zT of 1.18 at 623 K, which is the best result for the Cu3SbSe4-based materials in the same temperature region. Our results demonstrate that the microwave-assisted synthesis method is capable of fabricating Cu based ternary compounds with high thermoelectric performance.