A hierarchical layered architecture in thermoelectric materials works as an ad hoc methodology for strengthening the unique inherent properties. Herein, an excellent thermoelectric behavior in novel 2D copper iodide nanoflakes is demonstrated by compositing with Ti3C2 MXene nanoinclusions. The interlaced architecture of the CuI/Ti3C2 composite lifts the electrical conductivity over two orders by efficient charge transport mechanisms. The thermal conductivity of CuI/Ti3C2 composite is reduced by drastic suppression of mid‐ and high‐frequency phonons by interfacial energy barrier scattering. The structural engineering approach yields a massive power factor of 225 μW m−1 K−2 and a figure of merit value of 0.48 in CuI/5 vol% Ti3C2 composite. A straightforward approach of tuning the figure of merit in Earth‐abundant, nontoxic thermoelectric materials to develop future sustainable energy sources is established.

Two-dimensional (2D)-layered atomic arrangement with ultralow lattice thermal conductivity and ultrahigh figure of merit in single-crystalline SnSe drew significant attention among all thermoelectric materials. However, the processing of polycrystalline SnSe with equivalent thermoelectric performance as singlecrystal SnSe will have great technological significance. Herein, we demonstrate a high zT of 2.4 at 800 K through the optimization of intrinsic defects in polycrystalline SnSe via controlled alpha irradiation. Through a detailed theoretical calculation of defect formation energies and lattice dynamic phonon dispersion studies, we demonstrate that the presence of intrinsically charged Sn vacancies can enhance the power factor and distort the lattice thermal conductivity by phonon-defect scattering. Supporting our theoretical calculations, the experimental enhancement in the electrical conductivity leads to a massive power factor of 0.9 mW/mK 2 and an ultralow lattice thermal conductivity of 0.22 W/mK through the vacancy-phonon scattering effect on polycrystalline SnSe. The strategy of intrinsic defect engineering of polycrystalline thermoelectric materials can increase the practical implementation of low-cost and high-performance thermoelectric generators.

For decades, the widespread application of thermoelectric generators has been plagued by two major limitations: heat stagnation in its legs, which limits power conversion efficiency, and inherent brittleness of its constituents, which accelerates thermoelectric generator failure. While notable progress has been made to overcome these quintessential flaws, the state-of-the-art suffers from an apparent mismatch between thermoelectric performance and mechanical toughness. Here, we demonstrate an approach to potentially enhance the power conversion efficiency while suppressing the brittle failure in thermoelectric materials. By harnessing the enhanced thermal impedance induced by the cellular architecture of microlattices with the exceptional strength and ductility (>50% compressive strain) derived from partial carbonization, we fabricate three-dimensional (3D) architected thermoelectric generators that exhibit a specific energy absorption of ~30 J g−1 and power conversion efficiency of ~10%. We hope our work will improve future thermoelectric generator fabrication design through additive manufacturing with excellent thermoelectric properties and mechanical robustness.

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Thermoelectric composites are known for their enhanced power conversion performance via interfacial engineering and intensified mechanical, structural, and thermal properties. However, the selection of these nanoinclusions, for example, their type, size effect, volume fraction, distribution uniformity, coherency with host, carrier dynamics, and physical stability, plays a crucial role in modifying the host material thermoelectric properties. In this Review, we classify the nanoinclusions into five types: carbon allotropes, secondary thermoelectric phases, metallic materials, insulating oxides, and others. On the basis of the classification, we discuss the mechanisms involved in improving the ZT of nanocomposites involving reduction of thermal conductivity (κ) by phonon scattering, improving the Seebeck coefficient (α) via energy filtering effect and the electrical conductivity (σ) by carrier injection or carrier channeling. Comprehensibly, we validate that adding nanoinclusions with high electrical and low thermal conductivity as compared to the matrix material is the best way to optimize the interlocked thermoelectric parameters. Thus, collective doping and nanoinclusions in thermoelectric materials is the best possible solution to achieve a higher power conversion efficiency equivalent to other renewable energy technologies.