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Recently, rock-salt lead-free chalcogenide SnTe-based thermoelectric (TE) materials have been considered an alternative to PbTe because of the nontoxic properties of Sn as compared to Pb. However, high carrier concentration that originated from intrinsic Sn vacancies and relatively high thermal conductivity of pristine SnTe lead to poor TE efficiency, which makes room for improving its TE properties. In this study, we present that the Na incorporation into the SnTe matrix is helpful for modifying the electronic band structure, optimization of carrier concentration, introducing dislocations, and kink planes; benefiting from these synergistic effects obviates the disadvantages of SnTe and makes a significant improvement in TE performance. We reveal that Na favorably impacts the structure of electronic bands by valence, conduction band engineering, leading to a nice enhancement in the Seebeck coefficient, which exhibits the highest power factor value of 37.93 μWcm

A novel and conjugated 2D 250-HADQ COF exhibits a high specific surface area and excellent thermal stability yielding high values of gravimetric capacitance and energy density in two-electrode double-layer supercapacitor cells.

Owing to the unique features, such as mechanically robust, low-toxic, high stability, and high thermoelectric performance, CoSb3-based skutterudite materials are among art-of-the state thermoelectric candidates. In this work, we develop a facile in-situ method for the growth of well-crystallinity (Ag, Sn) co-doped CoSb3 thin films. This preparation method can efficiently control the dopant concentration and distribution in the thin films. Both the density functional theory calculation and the experimental results suggest that Sn and Ag dopants trend to enter the lattice and preferentially fill interstitial sites. Additionally, band structure calculation results suggest that the Fermi level moves into the conduction bands due to co-doping and eventually induces the increased electrical conductivity, which agrees with the optimization of carrier concentration. Moreover, an increase in the density of state after co-doping is responsible for the increased Seebeck coefficient. As a result, the power factors of (Ag, Sn) co-doped CoSb3 thin films are greatly enhanced, and the maximum power factor achieves over 0.3 mW m−1 K−2 at 623 K, which is almost two times than that of the un-doped CoSb3 film. Multiple microstructures, including Sb vacancies and Ag/Sn interstitial atoms as point defects, and a high density of lattice distortions coupled with nano-sized Ag-rich grains, lead to all scale phonon scatterings. As a result, a reduced thermal conductivity of ∼0.28 W m−1 K−1 and a maximum ZT of ∼0.52 at 623 K are obtained from (Ag, Sn) co-doped CoSb3 thin films. This study indicates our facile in-situ growth can be used to develop high-performance dual doped CoSb3 thins.

Te-free n-type Bi2O2Se is one of the promising thermoelectric materials due to its high chemical stability and eco-friendliness. However, its conversion efficiency reported so far is still low. Hen...

As an eco-friendly thermoelectric material, Cu2SnSe3 has recently drawn much attention. However, its high electrical resistivity ρ and low thermopower S prohibit its thermoelectric performance. Herein, we show that a widened band gap and the increased density of states are achieved via S alloying, resulting in 1.6 times enhancement of S (from 170 to 277 μV/K). Moreover, doping In at the Sn site can cause a 19-fold decrease of ρ and a 2.2 times enhancement of S (at room temperature) due to both multivalence bands' participation in electrical transport and the further enhancement of the density of states effective mass, which allows a sharp increase in the power factor. As a result, PF = 9.3 μW cm-1 K-2 was achieved at ∼800 K for the Cu2Sn0.82In0.18Se2.7S0.3 sample. Besides, as large as 44% reduction of lattice thermal conductivity is obtained via intensified phonon scattering by In-doping-induced formation of multidimensional defects, such as Sn vacancies, dislocations, twin boundaries, and CuInSe2 nanoprecipitates. Consequently, a record high figure of merit of ZT = 1.51 at 858 K is acquired for Cu2Sn0.82In0.18Se2.7S0.3, which is 4.7-fold larger than that of pristine Cu2SnSe3.

Rational design and synthesis of multifunctional electrocatalysts with high electrochemical activity and low cost are significantly important for new-generation lithium-sulfur (Li-S) batteries. Herein, N-doped FeP nanospheres decorated N doped carbon matrix is successfully synthesized by facile one-pot pyrolysis and in-situ phosphorization technique to mitigate the conversion kinetics and suppress the shuttle effect. The large specific surface area with mesopores can incorporate up to 81.5% sulfur, with the conductive carbon and nitrogen co-matrix providing Li

As a p-type thermoelectric material, Cu2SnSe3 (CSS) has recently drawn much attention, with its constituents being abundant and free of toxic elements. However, the low electrical conductivity σ and thermopower S of CSS prohibit its thermoelectric performance. Here, we show that through mechanical milling, a 14 times increase in σ, around a 2-fold rise in S and a 40% reduction in the lattice thermal conductivity κL (at 300 K) can be achieved, amazingly. Microstructural analysis combined with first-principles calculations reveal that the increased σ originates from the generated Sn vacancies , Se dangling bonds and the reconstructed Cu-Sn-terminated acceptor-like surface states; while the enhanced S comes mainly from the enhanced density of states effective mass caused by the Sn vacancies. In addition, the generated Sn vacancies and the in situ formed SnO2 nanoparticles give rise to strong phonon scattering, leading to the reduced κL. As a result, a maximum ZTm = 0.9 at 848 K is obtained for the CSS specimen milled for 2 h, which is ∼3 times larger than that of CSS milled for 0.5 h.

International audience; Searching for eco-friendly and earth-abundant materials to supersede traditional high-cost bismuth telluride for fabricating wearable devices is of great significance in thermoelectrics. In this work, promising flexible Cu2Se based thin films with high thermoelectric performance is successfully fabricated via a facile co-sputtering method. Experimental results indicate that excess Cu in Cu2Se films leads to the decrease of carrier concentration by suppressing the formation of Cu vacancies and donating electrons, benefiting to achieve high Seebeck coefficient. Moreover, Cu-excess Cu2Se films have highly (0l0) preferred orientation and extra high carrier mobility, maintaining the decent electrical conductivity in the whole measurement temperature range. Combined with the low thermal conductivity, a maximum ZT of 0.42 is obtained at 275 °C from the Cu-excess Cu2Se due to the simultaneous optimization both of electrical and heat transport. Subsequently, a flexible thermoelectric device assembled with high performance Cu2Se films exhibits a maximum power density of 4.28 Wm-2 at a temperature difference of 50 °C, which thermal stability is greatly improved after introducing a molybdenum buffer layer into electrode layer. Therefore, this work demonstrates that rational microstructure manipulations and connection technology improvement can achieve high performance in the flexible thermoelectric device, which possess potential in wearable applications.

Cu3SbSe4-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 Cu3SbSe4-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 Cu3Sb0.94Sn0.06Se4–ySy (y = 0, 0.5) embedded with Cu3SbSe3 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 Cu3Sb0.94Sn0.06Se3.5Se0.5. 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...

Flexible Bi

As an eco-friendly thermoelectric material, Cu

Although Bi2Te2.7Se0.3 is the best n-type thermoelectric material near room temperature, its energy-conversion efficiency η reported so far is still low. Hence, it is imperative to increase its η so as to realize widespread applications in heat recovery. Here, we show that through incorporation of Bi2Te3 (BT) nanoinclusions in Bi2Te2.7Se0.3 one can construct a large number of coherent phase boundaries and build effective interface potential barriers, based on which high electron mobility and energy-dependent carrier scattering are realized simultaneously. As a result, as large as 11% elevation of power factor is reached besides a large drop (53% at 300 K) of lattice thermal conductivity in the composite with 0.5 vol% BT nanoinclusions. Consequently, both a record high figure of merit ZTmax = 1.35 (at 414 K) and a record large ZTave = 1.28 are achieved in the operating temperature range of 300–525 K, which allow us to obtain an unprecedented conversion efficiency η = 10.5%. The present work demonstrates that incorporation of isostructural nanoinclusions in Bi2Te2.7Se0.3 is an effective approach to improve its thermoelectric performance.

As a p-type thermoelectric material, Cu2SnSe3 (CSS) has recently drawn much attention, with its constituents being abundant and free of toxic elements. However, the low electrical conductivity σ and thermopower S of CSS prohibit its thermoelectric performance. Here, we show that through mechanical milling, a 14 times increase in σ, around a 2-fold rise in S and a 40% reduction in the lattice thermal conductivity κL (at 300 K) can be achieved, amazingly. Microstructural analysis combined with first-principles calculations reveal that the increased σ originates from the generated Sn vacancies , Se dangling bonds and the reconstructed Cu-Sn-terminated acceptor-like surface states; while the enhanced S comes mainly from the enhanced density of states effective mass caused by the Sn vacancies. In addition, the generated Sn vacancies and the in situ formed SnO2 nanoparticles give rise to strong phonon scattering, leading to the reduced κL. As a result, a maximum ZTm = 0.9 at 848 K is obtained for the CSS specimen milled for 2 h, which is ∼3 times larger than that of CSS milled for 0.5 h.

International audience; Copper selenide (Cu2Se) is a promising thermoelectric material and α-phase Cu2Se provides relatively safe thermoelectric modules for thin film thermoelectric device in contrast to some toxic materials currently on the market. In this work, nanocrystalline Cu2Se thin film with uniform element distribution was fabricated at room temperature through an effective combination reaction method by implanting sputtered Cu+ ions into Se precursor. Then, self-assembled growth of Cu2Se thin films with desired α-phase and well crystallinity was successfully achieved with optimization of annealing temperature. Interestingly, the growth orientation has obviously affected by the annealing temperature, which significantly affects the thermoelectric properties. Consequently, the Seebeck coefficients increase with the increase in the orientation factor of the (0l0) preferred orientation, which enhances power factor. The high maximum power factor of 9.23 μWcm−1K−2 is achieved for α-Cu2Se thin film with (0l0) preferred orientation, demonstrating that the method used in this work has great potential in developing low-cost and high-performance thermoelectric thin films from relatively earth-abundant elements. © 2021 Elsevier B.V.

Recently, fabrication of high-efficiency miniature thermoelectric devices with thin films has attracted great attention. ZnSb-based thin films have been widely studied owing to their advantages of earth-abundant, eco-friendly, and excellent electron transport properties. However, its thermoelectric performance at room temperature is still low which extremely restricts its application. In this work, we report a high-power factor of 6.2 μWcm −1K−2 and a record-high thermoelectric figure of merit, ZT of 0.35 at room temperature from the non-stoichiometric ZnSb-based thin film, fabricated by a facile magnetron cosputtering technique. Extensive characterizations reveal that all the prepared films have a primary ZnSb phase with good crystallinity, leading to high electrical conductivity . Meanwhile, the carrier concentration is optimized with Zn addition, which contributes to a high Seebeck coefficient, resulting in a decent power factor. Simultaneously, the Zn-rich films also show nanopores , Zn-rich nanophases, and Zn 4Sb3 nano inclusions. These induced nanostructures enhance the scattering of medium- and long-wavelength phonons, contributing to the reduction of lattice thermal conductivity . This work demonstrates that rational nanostructure manipulations can achieve high performance in ZnSb thin films, which possess potential applications for the fabrication of miniature thermoelectric devices.

The sulfide compound Bi2SeS2 is an environmentally friendly thermoelectric material, which is as an analogy of the traditional compound Bi2S3. Here, a high ZT value of 1.04 at 773 K is obtained through synergistically tuning the electrical transport properties by using Cu and I as the dual carrier providers and suppressing the lattice thermal conductivity by forming the Cu-rich nano-precipitates. The dual carrier providers lead to exclusively high electrical conductivity and hence a large power factor over 650 μWm−1K−2 at 773 K. The atomic resolved annular dark field STEM reveals the interstitial Cu and S deficiency would result into the formation of BiCuS2 or Cu2S nano-precipitates and embed in the lattice of Bi2SeS2, serving as strong phonon scattering. This work suggested that nanostructured Bi2SeS2 is very promising for waste heat energy harvesting in the future.

n-type Bi2Te2.7Se0.3 (BTS) alloy is a state-of-the-art room temperature thermoelectric material used for refrigeration commercially. However, wide application is limited by its low performance. Here, we show that incorporation of nano-sized 3D topological insulator (3D-TI) Bi2Se3 in Bi2Te2.7Se0.3 bring about a large electron mobility and increased electrical conductivity owing to the enhanced contribution of topologically protected conducting surface states as well as large Seebeck coefficient due to energy dependent carrier scattering. Besides, the incorporation of 3D-TI nanoinclusions leads to enhanced phonon scattering. As a result, addition of 0.3 vol% of Bi2Se3 in BTS results in ~ 36% increase in power factor and ~ 16% decrease in total thermal conductivity, leading to a large figure of merit ZTmax = 1.28 (at 375 K) and a large average ZTave = 1.16 (at T = 300–525 K), which are 62% and 59% greater than that of BTS, respectively.

Although n-type Bi2Te3-based alloys are state-of-the-art thermoelectric material, their efficiency is still too low to satisfy its wide applications. Hence, it is imperative to improve the thermoelectric performance of n-type Bi2Te2.7Se0.3 (BTS). Here, we show that through a facile method of Sn addition in BTS a new SnxBi2Te2.7Se0.3 based nanocomposite embedded with in-situ formed SnBi and Te nanoinclusions ((SnBi + Te)/SnxBi2Te2.7Se0.3) is constructed, and its thermoelectric performance is enhanced substantially as compared to pristine BTS. Specifically, addition of 0.2 wt% of Sn in BTS causes 38% increase in power factor (PF) and 40% reduction in lattice thermal conductivity. The increased PF mainly comes from elevated Seebeck coefficient due to intensified energy dependent electron scattering caused by the interface potentials; while the reduced thermal conductivity originates from enhanced phonon scattering by the embedded nanoinclusions. Consequently, both high maximum figure of merit ZT (ZTmax = 1.11 at ~370 K) and large average ZT (ZTave = 1.03 at T = 300 K–500 K) are achieved for this sample, which are respectively 76% and 80% higher than those of BTS studied here.

As an environmentally friendly thermoelectric material with its constituents being free of Pb/Te, tetrahedrite Cu12Sb4S13 absorbs much research interest. However, its low thermoelectric performance inhibits its applications. Here, we show that through dual substitution of Se for S and Zn for Cu in the compound, both the electrical conductivity and the thermopower are enhanced, leading to the elevation of the power factor as high as ∼33% (at 723 K). Analyses indicate that the substitution of Se for S gives rise to changes in stoichiometry of Cu12Sb4S13 through precipitation of impurity phase Cu3SbS4, which causes variations of S vacancies and hole concentrations, while Zn2+ substitution for Cu1+ introduces donors, both of which tune and optimize the carrier concentration. Besides, the lattice thermal conductivity of dual substituted samples is reduced by as low as ∼30% (at 723 K) due to intensified phonon scattering of the impurities (Se and Zn). As a result, a large figure of merit ZT = 0.9 (at 723 K) is achieved in Cu12−yZnySb4S12.8Se0.2 samples with y = 0.025 and 0.05, which is ∼41% higher than that of pristine tetrahedrite Cu12Sb4S13, indicating that dual substitution is an effective approach to improving its thermoelectric performance.