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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.

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.

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.

International audience; Flexible Bi2Te3-based thermoelectric devices can function as power generators for powering wearable electronics or chip-sensors for internet-of-things. However, the unsatisfied performance of n-type Bi2Te3 flexible thin films significantly limits their wide application. In this study, a novel thermal diffusion method is employed to fabricate n-type Te-embedded Bi2Te3 flexible thin films on flexible polyimide substrates, where Te embeddings can be achieved by tuning the thermal diffusion temperature and correspondingly result in an energy filtering effect at the Bi2Te3/Te interfaces. The energy filtering effect can lead to a high Seebeck coefficient approximate to 160 mu V K-1 as well as high carrier mobility of approximate to 200 cm(2) V-1 s(-1) at room-temperature. Consequently, an ultrahigh room-temperature power factor of 14.65 mu W cm(-1) K-2 can be observed in the Te-embedded Bi2Te3 flexible thin films prepared at the diffusion temperature of 623 K. A thermoelectric sensor is also assembled through integrating the n-type Bi2Te3 flexible thin films with p-type Sb2Te3 counterparts, which can fast reflect finger-touch status and demonstrate the applicability of as-prepared Te-embedded Bi2Te3 flexible thin films. This study indicates that the thermal diffusion method is an effective way to fabricate high-performance and applicable flexible Te-embedded Bi2Te3-based thin films.

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.