The long-standing popularity of thermoelectric materials has contributed to the creation of various thermoelectric devices and stimulated the development of strategies to improve their thermoelectric performance. In this review, we aim to comprehensively summarize the state-of-the-art strategies for the realization of high-performance thermoelectric materials and devices by establishing the links between synthesis, structural characteristics, properties, underlying chemistry and physics, including structural design (point defects, dislocations, interfaces, inclusions, and pores), multidimensional design (quantum dots/wires, nanoparticles, nanowires, nano- or microbelts, few-layered nanosheets, nano- or microplates, thin films, single crystals, and polycrystalline bulks), and advanced device design (thermoelectric modules, miniature generators and coolers, and flexible thermoelectric generators). The outline of each strategy starts with a concise presentation of their fundamentals and carefully selected examples. In the end, we point out the controversies, challenges, and outlooks toward the future development of thermoelectric materials and devices. Overall, this review will serve to help materials scientists, chemists, and physicists, particularly students and young researchers, in selecting suitable strategies for the improvement of thermoelectrics and potentially other relevant energy conversion technologies.

Advanced Thermoelectric Design: From Materials and Structures to Devices

Dielectric capacitors with a high operating temperature applied in electric vehicles, aerospace and underground exploration require dielectric materials with high temperature resistance and high energy density. 

High-temperature polyimide dielectric materials for energy storage: theory, design, preparation and properties

Advances in the design and assembly of flexible thermoelectric device

Low-cost and large-area solar-thermal absorbers with superior spectral selectivity and excellent thermal stability are vital for efficient and large-scale solar-thermal conversion applications, such as space heating, desalination, ice mitigation, photothermal catalysis, and concentrating solar power. Few state-of-the-art selective absorbers are qualified for both low- ( 600 °C) applications due to insufficient spectral selectivity or thermal stability over a wide temperature range. Here, a high-performance plasmonic metamaterial selective absorber is developed by facile solution-based processes via assembling an ultrathin (≈120 nm) titanium nitride (TiN) nanoparticle film on a TiN mirror. Enabled by the synergetic in-plane plasmon and out-of-plane Fabry-Perot resonances, the all-ceramic plasmonic metamaterial simultaneously achieves high, full-spectrum solar absorption (95%), low mid-IR emission (3% at 100 °C), and excellent stability over a temperature range of 100-727 °C, even outperforming most vacuum-deposited absorbers at their specific operating temperatures. The competitive performance of the solution-processed absorber is accompanied by a significant cost reduction compared with vacuum-deposited absorbers. All these merits render it a cost-effective, universal solution to offering high efficiency (89-93%) for both low- and high-temperature solar-thermal applications.

Solution‐Processed All‐Ceramic Plasmonic Metamaterials for Efficient Solar–Thermal Conversion over 100–727 ° C

Nanocermet is a promising candidate for solar thermal applications and can be commercialized owing to its excellent photothermal conversion efficiencies, controllable composition and simple preparation technologies. Magnetron sputtering technology is the commonest for industrial preparation of nanocermet solar selective absorber coatings (SSACs), which usually involves a complicated co-sputtering process (multiple targets work simultaneously). Such a complex process greatly increases the preparation cost. Hence, it is urgent to simplify the production process. In this review, the concept of self-doping is firstly proposed to design cermet-based SSACs, which obviously simplifies the preparation process while maintains their own optical properties. Then, a detailed discussion about four types of self-doped cermet SSACs has been performed. The industrial preparation processes of SSACs including vacuum solar collector tube and metal strip with SSACs are introduced. Finally, the applications of SSACs in terms of different temperatures are also presented. In addition, the short board and development trend are also discussed, which is of great significance to obtain high performance SSACs.

Solar thermal harvesting based on self-doped nanocermet: Structural merits, design strategies and applications

Zintl compounds are considered to be potential thermoelectric materials due to their “phonon glass electron crystal” (PGEC) structure. A promising Zintl-phase thermoelectric material, 2-1-2–type Eu2ZnSb2 (P63/mmc), was prepared and investigated. The extremely low lattice thermal conductivity is attributed to the external Eu atomic layers inserted in the [Zn2Sb2]2- network in the structure of 1-2-2–type EuZn2Sb2 ( P 3 ¯ m 1 ) , as well as the abundant inversion domain boundary. By regulating the Zn deficiency, the electrical properties are significantly enhanced, and the maximum ZT value reaches ∼1.0 at 823 K for Eu2Zn0.98Sb2. Our discovery provides a class of Zintl thermoelectric materials applicable in the medium-temperature range.

https://www.pnas.org/content/pnas/116/8/2831.full.pdf

Zintl-phase Eu2ZnSb2: A promising thermoelectric material with ultralow thermal conductivity.

High performance wearable thermoelectric generators using Ag2Se films with large carrier mobility

Enhanced spectral selectivity through the quasi-optical microcavity based on W-SiO2 cermet

A review of spectral controlling for renewable energy harvesting and conserving

Wearable thermoelectric generators have great potential to be utilized as the power supply for wearable electronics. However, the limited temperature difference across the thermoelectric generators significantly degrades the output performance, which is anticipated to be improved by enhancing the thermal radiation at the cold side without extra energy consumption. In this paper, the impact of thermal radiation on the performance of thermoelectric generators in different environments is simulated and the enhanced performance in a wearable thermoelectric generator combined with a radiative cooling coating is experimentally verified. Compared with the pristine device, the wearable thermoelectric generator with radiative cooling coating can not only achieve an ≈128% improvement of output power in exposed environments, but also exhibit an ≈96% improvement of output power in non-exposed environments. The indoor output performance of the wearable thermoelectric generator with a radiative cooling coating due to its stable voltage output is extensively investigated, which shows an output power density of ≈5.5 μW cm-2 at the indoor temperature of 295 K, doubled that without a radiative cooling coating. This work paves a new way for further enhancing the performance of thermoelectric generators via passive radiative cooling.

Yijie Liu

Papers

Zintl-phase Eu2ZnSb2: A promising thermoelectric material with ultralow thermal conductivity.

High performance wearable thermoelectric generators using Ag2Se films with large carrier mobility

Enhanced spectral selectivity through the quasi-optical microcavity based on W-SiO2 cermet

A review of spectral controlling for renewable energy harvesting and conserving

Passive Radiative Cooling Enables Improved Performance in Wearable Thermoelectric Generators.