Tunable quantum gaps to decouple carrier and phonon transport leading to high-performance thermoelectrics

Abstract

Thermoelectrics enable direct heat-to-electricity transformation, but their performance has so far been restricted by the closely coupled carrier and phonon transport. Here, we demonstrate that the quantum gaps, a class of planar defects characterized by nano-sized potential wells, can decouple carrier and phonon transport by selectively scattering phonons while allowing carriers to pass effectively. We choose the van der Waals gap in GeTe-based materials as a representative example of the quantum gap to illustrate the decoupling mechanism. The nano-sized potential well of the quantum gap in GeTe-based materials is directly visualized by in situ electron holography. Moreover, a more diffused distribution of quantum gaps results in further reduction of lattice thermal conductivity, which leads to a peak ZT of 2.6 at 673 K and an average ZT of 1.6 (323–723 K) in a GeTe system. The quantum gap can also be engineered into other thermoelectrics, which provides a general method for boosting their thermoelectric performance.

Grain Boundary Complexions Enable a Simultaneous Optimization of Electron and Phonon Transport Leading to High‐Performance GeTe Thermoelectric Devices

“…The highest ZT avg value of 1.31 was obtained in Ge 0.78 Ga 0.01 Pb 0.1 Sb 0.07 Te, which outperforms many GeTe‐based alloys reported in the literature, [ 35,59–63 ] though higher ZT avg values have also been achieved recently. [ 10,64,65 ]…”

“…The highest ZT avg value of 1.31 was obtained in Ge 0.78 Ga 0.01 Pb 0.1 Sb 0.07 Te, which outperforms many GeTe-based alloys reported in the literature, [35,[59][60][61][62][63] though higher ZT avg values have also been achieved recently. [10,64,65] Besides TE performance, thermal stability is also a critical factor for obtaining high-performance and durable TE devices, especially for GeTe-based alloys with a phase-transition behavior. Figure 2f shows the temperature-dependent relative length variation (dL/L 0 ), where the slope of corresponding curves indicates the coefficient of thermal expansion (CTE).…”

Abnormal behavior of preferred formation of the cationic vacancies from the interior in a γ-GeSe monolayer with the stereo-chemical antibonding lone-pair state

“…Group IV monochalcogenides MX (M = Ge, Sn, Pb; X = S, Se, Te) are a family of emerging 2D layered materials which are gaining extensive interest in thermoelectric, 1,2 photocatalysis, 3,4 and ferroelectric 5,6 fields. Among the various MXs, GeSe deserves particular attention, owing to recent papers reporting on its outstanding photovoltaic efficiency, 7 excellent optoelectronic properties, 8 and electric-field induced room temperature antiferroelectric–ferroelectric phase transition, 9 as well as its inherent chemical stability and environmental sustainability.…”

Charge transfer engineering to achieve extraordinary power generation in GeTe-based thermoelectric materials

“…Large local structure distortion at and around the planar defects as confirmed by the strain distribution analysis ( Fig. 4I ) would generate strong anharmonic phonon scattering, and simultaneously, the transport of carriers may be maintained ( 47 ).…”