High‐Performance GeTe‐Based Thermoelectrics: from Materials to Devices

Abstract

m ), [52] enlarging band degeneracy (N V ), [43] and introducing resonant energy levels, [26] can also tune n p effectively. Taking Ge 1−x−y Sb x Zn y Te as an example, Zn doping can reduce the energy offset (ΔE) between L and Σ point. [52] The minimization of thermal transport properties is mainly achieved through suppressing the electrical property-independent κ l . [53][54][55][56][57] Thermoelectric materials with High-performance GeTe-based thermoelectrics have been recently attracting growing research interest. Here, an overview is presented of the structural and electronic band characteristics of GeTe. Intrinsically, compared to lowtemperature rhombohedral GeTe, the high-symmetry and high-temperature cubic GeTe has a low energy offset between L and Σ points of the valence band, the reduced direct bandgap and phonon group velocity, and as a result, high thermoelectric performance. Moreover, their thermoelectric performance can be effectively enhanced through either carrier concentration optimization, band structure engineering (bandgap reduction, band degeneracy, and resonant state engineering), or restrained lattice thermal conductivity (phonon velocity reduction or phonon scattering). Consequently, the dimensionless figure of merit, ZT values, of GeTe-based thermoelectric materials can be higher than 2. The mechanical and thermal stabilities of GeTe-based thermoelectrics are highlighted, and it is found that they are suitable for practical thermoelectric applications except for their high cost. Finally, it is recognized that the performance of GeTe-based materials can be further enhanced through synergistic effects. Additionally, proper material selection and module design can further boost the energy conversion efficiency of GeTe-based thermoelectrics.

Thermoelectric Generators: Alternative Power Supply for Wearable Electrocardiographic Systems

“…[57] Within the low-temperature range (<500 K), the zT values of these materials are generally lower than unity. [14,27,58] Among them, Bi 2 Te 3 - [31,[59][60][61] and Bi 0.5 Sb 1.5 Te 3based [62][63][64] materials show room-temperature zT values of >1 (Figure 6a) and have an applicable energy conversion efficiency for wearable electrocardiographic systems. [16,27,65,66] However, the rigidity of these materials is a major obstacle because it significantly effects the comfort of the person wearing the system and the coupling of the device to the body heat source.…”

High Power Density Thermoelectric Generators with Skutterudites

“…Thermoelectric materials have the ability to directly and reversibly convert a thermal gradient into electrical energy, offering an elegant and versatile way to recover energy from any heat source. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] Thermoelectric generators (TEGs), consisting of n-and p-type legs composed of doped semiconductors, have been mostly used as reliable power supplies for rovers and deepspace probes. [10,11] Despite being an attractive solid-state technology primarily due to its high reliability and absence of greenhouse gas emissions, the limited use of TEGs in terrestrial applications is tied to their output performances, still surpassed by other green energyconversion technologies such as solar cells.…”

Multiscale architectures boosting thermoelectric performance of copper sulfide compound

“…Specifically, σ and S can hardly increase simultaneously as these two parameters are coupled via carrier concentration [ 13 , 14 ]. Besides, the reduction of κ often degrades the carrier mobility and thus σ [ 15 – 17 ]. Conflicts between these properties impede the limitless enhancement of zT , where a compromise is necessary to optimize zT .…”