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Crystalline red phosphorus has very recently emerged as a stable and cost-effective semiconductor material. However, despite its potentiality in electronics and optoelectronics, the widespread appl...

The recent interest in wearable electronics suggests flexible thermoelectrics as candidates for the power supply. Herein, we report a solution process to fabricate flexible Sb2Te3 thermoelectric th...

Thermoelectric power generation offers a promising way to recover waste heat. The geometrical design of thermoelectric legs in modules is important to ensure sustainable power generation but cannot be easily achieved by traditional fabrication processes. Herein, we propose the design of cellular thermoelectric architectures for efficient and durable power generation, realized by the extrusion-based 3D printing process of Cu2Se thermoelectric materials. We design the optimum aspect ratio of a cuboid thermoelectric leg to maximize the power output and extend this design to the mechanically stiff cellular architectures of hollow hexagonal column- and honeycomb-based thermoelectric legs. Moreover, we develop organic binder-free Cu2Se-based 3D-printing inks with desirable viscoelasticity, tailored with an additive of inorganic Se82− polyanion, fabricating the designed topologies. The computational simulation and experimental measurement demonstrate the superior power output and mechanical stiffness of the proposed cellular thermoelectric architectures to other designs, unveiling the importance of topological designs of thermoelectric legs toward higher power and longer durability., The geometrical design of thermoelectric legs in modules is key for sustainable power generation but can be hardly achieved by traditional fabrication process. Here, the authors develop an extrusion-based 3D printing process of Cu2Se thermoelectric materials for efficient power generation.

Compared with the large plastic deformation observed in ductile metals and organic materials, inorganic semiconductors have limited plasticity (0.2%) due to their intrinsic bonding characters, restricting their widespread applications in stretchable electronics. Herein, the solution-processed synthesis of ductile α-Ag

Given the recent interest in portable and wearable electronics, thin film thermoelectrics are regarded as promising candidates for the power supply of self-powered systems. Moreover, the solution-processed fabrication method offers a cost-effective and convenient route to fabricate thin film-based thermoelectric devices. In this chapter, we review the recent progress in the development of thermoelectric solution-based inks, processing techniques, and solution-processed devices, mainly focusing on metal chalcogenides. A summary of basic chemistry for the synthesis of thermoelectric solutions is included, as well as a discussion on various fabricated thin films with several examples of materials such as Bi2Te3, Sb2Te3, PbTe, Cu2Se, and SnSe. Finally, the outlook of this field with respect to the expansion of classes of materials as well as industrialization of thermoelectric thin films is presented.

Bipolar conduction in Bi-Te-based alloys is a critical barrier to high conversion efficiency in thermoelectric power generation applications. Herein, we investigate the effect of Te/Se ratio control on bipolar conduction in n-type Cu0.008Bi2(Te,Se)3. Based on the two-band model and Callaway model, we found that electronic and thermal transports of minority carriers (holes) were gradually decreased with an increase in Se content. The high-temperature power factor of Se-rich Cu0.008Bi2Te2.1Se0.9 was higher in value compared to reference Cu0.008Bi2Te2.7Se0.3 due to the weighted mobility ratio increase, and its bipolar thermal conductivity was significantly reduced simultaneously. As a result, a peak figure of merit (zT) of 0.92 was obtained at 440 K in Cu0.008Bi2Te2.1Se0.9.

Thermoelectric energy conversion offers a unique solution for generating electricity from waste heat. However, despite recent improvements in the efficiency of thermoelectric materials, the widespread application of thermoelectric generators has been hampered by challenges in fabricating thermoelectric materials with appropriate dimensions to perfectly fit heat sources. Herein, we report an extrusion-based three-dimensional printing method to produce thermoelectric materials with geometries suitable for heat sources. All-inorganic viscoelastic inks were synthesized using Sb2Te3 chalcogenidometallate ions as inorganic binders for Bi2Te3-based particles. Three-dimensional printed materials with various geometries showed homogenous thermoelectric properties, and their dimensionless figure-of-merit values of 0.9 (p-type) and 0.6 (n-type) were comparable to the bulk values. Conformal cylindrical thermoelectric generators made of 3D-printed half rings mounted on an alumina pipe were studied both experimentally and computationally. Simulations show that the power output of the conformal, shape-optimized generator is higher than that of conventional planar generators. Three-dimensional printing is changing the way we manufacture objects. Here, Kim et al. develop inks of inorganic thermoelectric materials to 3D print the legs of conformable thermoelectric generators, allowing waste heat recovery from hot water pipes.

Over the past decade, nanostructuring has become the core of thermoelectric (TE) material research because it creates numerous internal interfaces that provide an effective way to tune the electrical and/or thermal properties of TE materials. Herein, we report a synthesis of interface-engineered BiSbTe nanostructured TE materials by introducing chemically synthesized molecular Ten2− polyanions into BiSbTe particles, from which BiSbTe nanostructured materials with high-density Te interfacial layers are prepared in thin films and sintered pellets. These Te layers form the contact potential well at the BiSbTe-Te junction to realize energy dependent carrier scattering and scatter phonons effectively, thus resulting in simultaneous improvement in the electrical and thermal properties to increase the ZT value well above 1.3 ± 0.14 that is increased by 40% compared to bulk BiSbTe. The findings of current study can open up new chemical design spaces for interface-engineered electronic and TE materials.

We report a strategy toward the synthesis of colloidal nanocrystals capped with inorganic molybdenum and tungsten sulfide ligands. MoS4(2-) and WS4(2-) thiometalates were utilized to replace organic ligands capping a wide range of nanocrystals such as metals, semiconductors, and well-conserved primary properties of nanocrystals in polar media. Especially, MoS4(2-)- and WS4(2-)-capped CdSe nanocryatals showed the dramatic enhancement of photoluminescence properties by the photo-oxidation treatment, which originated from the preferential formation of MoSxOy layers on the CdSe surface. The highest quantum yield reached up to 51%. Furthermore, we studied the charge-transport properties of MoS4(2-)-capped PbS nanocryatals by the fabrication of a field-effect transistor and photodetectors. Finally, MoS4(2-)- and WS4(2-)-capped nanocrystals were used for the production of two-dimensional MoS2 and WS2 thin layers on nanostructures by heat treatment. Such versatility of these thiometalate ligands offers an additional degree of control over the functionality of nanocrystals for optoelectronic and catalytic applications.

Porous semiconductors attract great interest due to their unique structural characteristics of high surface area as well as their intrinsic optical and electronic properties. In this study, synthesis of inorganic-organic 2D CdSe slabs-diaminooctane (DAO) porous quantum net structures is demonstrated. It is found that the hybrid 2D CdSe-DAO lamellar structures are disintegrated into porous net structures, maintaining an ultrathin thickness of ≈1 nm in CdSe slabs. Furthermore, the CdSe slabs in quantum nets show the highly shifted excitonic transition in the absorption spectrum, demonstrating their strongly confined electronic structures. The possible formation mechanism of this porous structure is investigated with the control experiments of the synthesis using n-alkyldiamines with various hydrocarbon chain lengths and ligand exchange of DAO with oleylamine. It is suggested that a strong van der Waals interaction among long chain DAO may exert strong tensile stress on the CdSe slabs, eventually disintegrating slabs. The thermal decomposition of CdSe-DAO quantum nets is further studied to form well-defined CdSe nanorods. It is believed that the current CdSe-DAO quantum nets will offer a new type of porous semiconductors nanostructures under a strong quantum-confinement regime, which can be applied to various technological areas of catalysts, electronics, and optoelectronics.

The growing concern over the depletion of hydrocarbon resources, and the adverse environmental effects associated with their use, has increased the demand for renewable energy sources. Thermoelectric (TE) power generation from waste heat has emerged as a renewable energy source that does not generate any pollutants. Recently, ink-based processing for the preparation of TE materials has attracted tremendous attention because of the simplicity in design of power generators and the possibility of cost-effective manufacturing. In this progress report, recent advances in the development of TE inks, processing techniques, and ink-fabricated devices are reviewed. A summary of typical formulations of TE materials as inks is included, as well as a discussion on various ink-based fabrication methods, with several examples of newly designed devices fabricated using these techniques. Finally, the prospects of this field with respect to the industrialization of TE power generation technology are presented.