Design of Highly Efficient Thermoelectric Materials: Tailoring Reciprocal‐Space Properties by Real‐Space Modification

Abstract

Although restricted by the poor performance at present, thermoelectric materials for power-generation devices and solid-state Peltier coolers still possess unlimited vitality, thus capturing considerable attention. Understanding and manipulating the electrical and thermal transport mechanisms in thermoelectrics play significant roles in tailoring the properties of various thermoelectric materials. The transport behavior of electrons and phonons are closely related to the chemical composition and structure, which are defined in real space. Meanwhile, transport properties are also contingent on the band structure and phonon spectrum, both of which are represented in the reciprocal-space first Brillouin zone. Real space and reciprocal space are bridged by the Fourier transform, and the combination of real-space and reciprocal-space properties will provide more possibilities for regulating transport characteristics. Herein, a compendious discussion of the internal connection between real space and reciprocal space, and the underlying physics and chemistry is presented. Then, how the relationship between real and reciprocal space provides additional insights to govern electrical and thermal transport parameters is elaborated upon, thereby enabling the discovery and optimization of thermoelectric materials. In conclusion, specific challenges and feasible directions are discussed.

Defects Engineering with Multiple Dimensions in Thermoelectric Materials

“…According to Equation (12), if the influence on the carrier mobility can be neglected, the larger DOS at the Fermi level will devote to a larger Seebeck coefficient. The resonant doping means inducing dopant atoms to create resonant levels, which expressly increases the DOS around the Fermi level and thereby contribute to an enhanced Seebeck coefficient.…”

“…In fact, most of the advanced thermoelectric materials are doped materials, which emphasize the significance of 0D point defects in thermoelectric materials. Benefited from the thermoelectric transport theories and concepts, now we have recognized that point defects have an impact on both band structure and transport behavior of carriers and phonons [8,[11][12][13]. However, for the diversity and sensibility to the composition and the preparation process, accurate characterization and theoretical simulation to judge the type and distribution of point defects in the material should also be taken seriously.…”

Inorganic thermoelectric materials: A review

“…To generate high voltage, a material with a large S is required. According to the Boltzmann transport theory, S and σ, for a metal and a degenerate semiconductor with single parabolic band model and energy‐independent scattering approximation, could be defined as: where k B , e , h , n , and m* defines the Boltzmann constant, electrical charge carrier, Planck's constant, carrier concentration (/cm 3 ), and effective mass of the carrier, respectively . Concurrently, the thermocouple, a building block of TEG, will be used to generate electricity, hence, the thermocouple must be made of materials with high σ, could be defined as: where μ , τ, and m b defines the mobility of charge carriers, carrier relaxation time, and band mass, respectively.…”

“…Recently, a number of reviews on TE materials have been published that, in summary, mainly focused on bulk TE materials, both inorganic and organic TE materials, progress and emerging TE materials, design of advanced TE materials, and high efficiency TE materials . Nonetheless, to the best of the authors’ knowledge, there is no systematic review highlighting the major problems, as well as the optimization techniques of fundamental properties, which are directly related to the efficiency of inorganic TE materials at different temperature range.…”

Understanding the Band Engineering in Mg2Si‐Based Systems from Wannier‐Orbital Analysis

“…n-type Mg 2 Si 1−x Sn x solid solution has become one of the most representative examples of band engineering in the thermoelectric field. [7][8][9][10][11][12] In 2006, Zaitsev et al predicted that the heavy and light conduction bands of Mg 2 B (B = Si, Ge, Sn) would certainly converge in their solid solutions. [13] In Mg 2 Si 0.4 Sn 0.6 and Mg 2 Si 0.6 Sn 0.4 , the similar ZTs of 1.1 were achieved.…”