Chalcopyrite compound CuGaTe2 is the focus of much research interest due to its high power factor. However, its high intrinsic lattice thermal conductivity seriously impedes the promotion of its thermoelectric performance. Here, it is shown that through alloying of isoelectronic elements In and Ag in CuGaTe2, a quinary alloy compound system Cu1−xAgxGa0.4In0.6Te2 (0 ≤ x ≤ 0.4) with complex nanosized strain domain structure is prepared. Due to strong phonon scattering mainly by this domain structure, thermal conductivity (at 300 K) drops from 6.1 W m−1 K−1 for the host compound to 1.5 W m−1 K−1 for the sample with x = 0.4. As a result, the optimized chalcopyrite sample Cu0.7Ag0.3Ga0.4In0.6Te2 presents an outstanding performance, with record‐high figure of merit (ZT) reaching 1.64 (at 873 K) and average ZT reaching 0.73 (between ≈300 and 873 K), which are ≈37 and ≈35% larger than the corresponding values for pristine CuGaTe2, respectively, demonstrating that such domain structure arising from isoelectronic multielement alloying in chalcopyrite compound can effectively suppress its thermal conductivity and elevate its thermoelectric performance remarkably.
Flexible Bi 2 Te 3 ‐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 Bi 2 Te 3 flexible thin films significantly limits their wide application. In this study, a novel thermal diffusion method is employed to fabricate n‐type Te‐embedded Bi 2 Te 3 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 Bi 2 Te 3 /Te interfaces. The energy filtering effect can lead to a high Seebeck coefficient ≈160 µV K −1 as well as high carrier mobility of ≈200 cm 2 V −1 s −1 at room‐temperature. Consequently, an ultrahigh room‐temperature power factor of 14.65 µW cm −1 K −2 can be observed in the Te‐embedded Bi 2 Te 3 flexible thin films prepared at the diffusion temperature of 623 K. A thermoelectric sensor is also assembled through integrating the n‐type Bi 2 Te 3 flexible thin films with p‐type Sb 2 Te 3 counterparts, which can fast reflect finger‐touch status and demonstrate the applicability of as‐prepared Te‐embedded Bi 2 Te 3 flexible thin films. This study indicates that the thermal diffusion method is an effective way to fabricate high‐performance and applicable flexible Te‐embedded Bi 2 Te 3 ‐based thin films.
As an eco-friendly thermoelectric material, Cu 2 SnSe 3 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 19fold 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 Cu 2 Sn 0.82 In 0.18 Se 2.7 S 0.3 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 CuInSe 2 nanoprecipitates. Consequently, a record high figure of merit of ZT = 1.51 at 858 K is acquired for Cu 2 Sn 0.82 In 0.18 Se 2.7 S 0.3 , which is 4.7-fold larger than that of pristine Cu 2 SnSe 3 .
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