Min Hong

The multiple valence band edges of GeTe provide an important degree of freedom for optimizing thermoelectric transport properties. However, conventional multielement co-doping strategies employed to achieve valence band convergence often introduce additional carrier scattering centers, leading to substantial mobility degradation and limiting further improvement of thermoelectric performance. To address this challenge, MnTe alloying is applied to high-mobility GeTe films grown using an optimized epitaxial buffer layer structure, yielding (GeTe)x(MnTe)y films that exhibit valence band convergence while retaining relatively high carrier mobility. Dilute MnTe alloying effectively tailors the valence band structure of GeTe, enabling the optimization of carrier transport in the (GeTe)36(MnTe)0.5 film, which exhibits a Seebeck coefficient of 110.14 μVK–1, a hole concentration of 2.56 × 1020 cm–3, and a carrier mobility of 70.2 cm2V–1s–1. The balance between an enhanced Seebeck coefficient and relatively high carrier mobility results in a room-temperature power factor of 3.49 mWm–1K–2, surpassing values reported for GeTe-based bulk materials. This work demonstrates an effective strategy for mitigating the trade-off between a large Seebeck coefficient and high carrier mobility in GeTe, providing valuable insights into the development of GeTe-based thin films for potential near-room-temperature applications.

Superlattice films are promising candidates for obtaining excellent thermoelectric performance because the hetero-interface can effectively regulate both carrier and phonon transport. However, the atomic and electronic structures at the hetero-interface remain largely unexplored, limiting the deep understanding of interfacial effects. Here, 1T′-MoTe2/Bi2Te3 quantum-dot films were fabricated for investigating the 1T′-MoTe2/Bi2Te3 hetero-interface and its effect on electrical transport. Atomic-scale characterizations indicate apparent Mo doping at the hetero-interface, while band structure calculations and transport measurements reveal that Mo doping can reconstruct the conduction band and enhance band degeneracy, leading to a large carrier effective mass of ∼1.6 m0. Meanwhile, spectroscopy measurements verify donor-like states and local band bending at the hetero-interface, which introduce modulation doping and thereby enable synergistically optimized electron density and carrier mobility. As a result, the best (1T′-MoTe2)0.8(Bi2Te3)12 film achieves a peak power factor of ∼3.74 mW m–1 K–2 at 325 K. These findings provide new insights of interfacial effects on synergistically optimizing carrier transport and electrical properties of thermoelectric superlattice or quantum-dot films.

Developing single‐atom catalysts (SACs) with efficient atomic usage and well‐defined coordination environments is pivotal for addressing limitations in redox kinetics and durability in lithium‐oxygen (Li‐O ₂ ) batteries. Herein, an efficient yet broadly applicable ball‐milling followed by pyrolysis approach for the synthesis of bi‐metal Fe, Co SACs supported on a graphitic carbon nitride (g‐C ₃ N ₄ ) matrix is proposed. The synthesis involves a top‐down approach, where Fe and Co metals are atomized and stabilized on g‐C ₃ N ₄ support, facilitating uniform distribution of isolated metal atoms while inhibiting aggregation. This approach promotes the formation of coexisting Fe‐N ₄ and Co‐N ₄ single‐atom sites anchored on distinct triazine units within g‐C ₃ N ₄ , where the Co‐N ₄ sites serve primarily as electronic modulators of the Fe‐centred active sites. The electronic interplay between the Co and Fe‐N ₄ sites within the g‐C ₃ N ₄ framework modulates the local electronic structure and optimizes the adsorption energetics of LiO ₂ intermediates, thereby accelerating both the oxygen reduction reaction and oxygen evolution reaction. As a result, the resulting catalysts deliver enhanced discharge capacity, lower overpotential, and prolonged cycling stability in Li‐O ₂ batteries. Overall, this work provides new insights into bi‐metal synergistic catalysis on g‐C ₃ N ₄ and highlights the critical role of active‐site engineering in governing Li‐O ₂ battery performance.

GeTe is a promising p‐type thermoelectric material for mid‐to‐high temperature applications because of its favorable electronic structure and excellent transport potential. However, its thermoelectric performance is still limited by excessive hole concentration and insufficient phonon scattering. Herein, rare‐earth La was co‐doped with Sb into GeTe via a melting–annealing–spark plasma sintering process, and the microstructure and thermoelectric transport properties of the samples were systematically evaluated. The thermoelectric characterization reveals that the co‐doping strategy significantly lowers the thermal conductivity without compromising electrical performance, thereby contributing to enhanced thermoelectric performance. The incorporation of Sb effectively regulates the hole concentration, preserves the electrical transport properties, and reduces the electronic thermal conductivity. In addition, La doping induces strain‐field fluctuations and local structural disorder, introducing multiscale micro‐ and nano‐structural features, which significantly strengthen phonon scattering and thereby suppress the lattice thermal conductivity. As a result, the Ge _0.89 Sb _0.1 La _0.01 Te composition achieves a peak zT of 2.8 at 793 K. These results demonstrate that rare earth‐assisted composition tuning is an effective strategy for improving the thermoelectric performance of GeTe‐based materials.

A central challenge in thermoelectric science is to break the intrinsic coupling between charge and heat transport. Herein, we demonstrate that thermally driven interface reconstruction in perovskite-modified skutterudites generates a hierarchical defect architecture that enables simultaneous regulation of electronic and phononic transport. By deliberately integrating point defects, (Pb, In)-rich nanoprecipitates, and multiscale pores into a unified interfacial framework, the reconstructed microstructure enhances carrier-energy selectivity while fostering broadband phonon scattering across multiple length scales. This synergy effectively mitigates the conventional electrical–thermal trade-off, yielding a peak zT of ∼1.76 at 773 K. A seven-couple thermoelectric generator assembled from the optimized material delivers a conversion efficiency of 8.1% under a temperature difference of 452 K. Collectively, these findings establish hierarchical interface reconstruction as a powerful strategy for transport decoupling and highlight defect-architecture engineering as a versatile design principle for thermoelectric energy conversion.

Chemical doping is a widely adopted strategy for optimizing carrier concentration and tailoring the electronic band structure in thermoelectric (TE) materials. However, in intrinsically cation‐deficient systems such as p ‐type GeTe, its effectiveness is often limited because the coexistence of abundant Ge vacancies and aliovalent dopants intensifies charge‐carrier scattering, thereby deteriorating carrier mobility ( µ ). Herein, we report a facile dopant‐free strategy to enhance the TE performance of Ge _0.94 Bi _0.06 Te through the construction of multi‐scale lattice strain. Increasing lattice symmetry and preserving ordered domain boundaries, combined with reduced deformation potential and prolonged carrier relaxation time, thereby improving µ and further boosting weighted mobility ( µ _W ) and power factor. Moreover, the engineered multi‐scale lattice defects strongly suppress lattice thermal conductivity ( κ _lat ), yielding an increased µ _W / κ _lat ratio within the optimal carrier concentration range, indicating weakened electron‐phonon coupling. Consequently, the peak figure of merit ( ZT ) of 2.21 and average ZT of 1.4 over 303–803 K are achieved. Furthermore, a single‐stage TE device fabricated using this material attains a conversion efficiency of 7.83% at a temperature difference of 400 K. This work highlights the effectiveness of strain engineering in decoupling electronic and phononic transport and demonstrates its broad applicability for developing high‐performance TE materials.

Silver selenide (Ag2Se) is a promising near-room-temperature thermoelectric material, but its narrow stoichiometric window and β–α phase transition complicate reproducible microstructure control. Here, we present a mismatch-assisted microstructure engineering strategy in which Ag2Se particles are treated with polyanionic ZnSe complexes and consolidated through the β–α transition to introduce ZnSe nanoprecipitates, Ag2Se/ZnSe interfaces, and local strain fields. The crystallographic mismatch between ZnSe and Ag2Se, together with the Zn2+/Ag+ size difference, amplifies phase-transition-induced deformation and promotes high-density dislocations with periodic strain modulations. This defect architecture suppresses grain coarsening, removes excess Ag, limits Ag-interstitial formation, and reduces lattice thermal conductivity through lattice softening and multiscale phonon scattering. Ag2Se–4%ZnSe nanocomposites achieve a peak zTmax of 1.13 at 369 K and a zTavg of 1.08 from 300 to 380 K, demonstrating mismatch-driven defect engineering through the β–α phase transition as a route for optimizing Ag2Se-based thermoelectrics.

Lead‐free GeTe‐based thermoelectrics exhibit strong potential; however, device performance is limited by the intrinsic ferroelectric phase transition and structural instability. Here, we propose a cooperative structural‐electronic regulation strategy that stabilizes the cubic phase and simultaneously enhances the thermoelectric and mechanical properties. AgSbTe ₂ alloying completely suppresses the ferroelectric transition over the entire operating temperature range, while complementary I doping produces refined single‐phase domains with well‐matched multi‐degree‐of‐freedom grain boundary networks, together with a precisely tuned band structure. These synergistic effects intensify phonon scattering, optimize carrier transport, and increase the effective mass, thereby elevating the power factor and substantially reducing the lattice thermal conductivity ( κ _L ), thereby significantly improving the weighted mobility ( µ _w )‐to‐ κ _L ratio. The optimized composition achieves a room‐temperature zT of ∼0.7 and a peak zT of ∼2.2 at 773 K, demonstrating superior performance from near‐ambient to intermediate temperatures. Concurrently, grain refinement effectively enhances mechanical integrity, yielding a compressive strength of ∼248 MPa. A 7‐pair power‐generation device delivers ∼11% efficiency at Δ T = 470 K, while a cooling device achieves a maximum Δ T _max of ∼65.6 K at 350 K. This study establishes a generalizable framework for concurrent phase stabilization and performance optimization, enabling scalable, high‐reliability GeTe‐based dual‐mode thermoelectric devices.