Thin Film Tin Selenide (SnSe) Thermoelectric Generators Exhibiting Ultralow Thermal Conductivity

Tin selenide (SnSe) has attracted much attention in the field of thermoelectrics since the discovery of the record figure of merit (ZT) of 2.6 ± 0.3 along the b‐axis of the material. The record ZT is attributed to an ultralow thermal conductivity that arises from anharmonicity in bonding. While it is known that nanostructuring offers the prospect of enhanced thermoelectric performance, there have been minimal studies in the literature to date of the thermoelectric performance of thin films of SnSe. In this work, preferentially orientated porous networks of thin film SnSe nanosheets are fabricated using a simple thermal evaporation method, which exhibits an unprecedentedly low thermal conductivity of 0.08 W m^?1 K^?1 between 375 and 450 K. In addition, the first known example of a working SnSe thermoelectric generator is presented and characterized.     

具有低热导率的Skutterudite类新型热电材料

结合声子散射机制介绍了近来报道的几种降低skutterudite类热电材料热导率的途径，为研究和发展skutterudite类热电材料提供一些思路和方法。     

Emerging Multifunctional Metal–Organic Framework Materials

Metal?organic frameworks (MOFs), also known as coordination polymers, represent an interesting type of solid crystalline materials that can be straightforwardly self‐assembled through the coordination of metal ions/clusters with organic linkers. Owing to the modular nature and mild conditions of MOF synthesis, the porosities of MOF materials can be systematically tuned by judicious selection of molecular building blocks, and a variety of functional sites/groups can be introduced into metal ions/clusters, organic linkers, or pore spaces through pre‐designing or post‐synthetic approaches. These unique advantages enable MOFs to be used as a highly versatile and tunable platform for exploring multifunctional MOF materials. Here, the bright potential of MOF materials as emerging multifunctional materials is highlighted in some of the most important applications for gas storage and separation, optical, electric and magnetic materials, chemical sensing, catalysis, and biomedicine.     

Bottom‐Up Fabrication of Semiconductive Metal–Organic Framework Ultrathin Films

Though generally considered insulating, recent progress on the discovery of conductive porous metal–organic frameworks (MOFs) offers new opportunities for their integration as electroactive components in electronic devices. Compared to classical semiconductors, these metal–organic hybrids combine the crystallinity of inorganic materials with easier chemical functionalization and processability. Still, future development depends on the ability to produce high‐quality films with fine control over their orientation, crystallinity, homogeneity, and thickness. Here self‐assembled monolayer substrate modification and bottom‐up techniques are used to produce preferentially oriented, ultrathin, conductive films of Cu‐CAT‐1. The approach permits to fabricate and study the electrical response of MOF‐based devices incorporating the thinnest MOF film reported thus far (10 nm thick).     

Epitaxial Growth of Oriented Metalloporphyrin Network Thin Film for Improved Selectivity of Volatile Organic Compounds

This study reports an oriented and homogenous cobalt‐metalloporphyrin network (PIZA‐1) thin film prepared by liquid phase epitaxial (LPE) method. The thickness of the obtained thin films can be well controlled, and their photocurrent properties can also be tuned by LPE cycles or the introduction of conductive guest molecules (tetracyanoquinodimethane and C₆₀) into the PIZA‐1 pores. The study of quartz crystal microbalance adsorption confirms that the PIZA‐1 thin film with [110]‐orientation presents much higher selectivity of benzene over toluene and p‐xylene than that of the PIZA‐1 powder with mixed orientations. These results reveal that the selective adsorption of volatile organic compounds highly depends on the growth orientations of porphyrin‐based metal‐organic framework thin films. Furthermore, the work will provide a new perspective for developing important semiconductive sensing materials with improved selectivity of guest compounds.     

热电薄膜与薄膜温差电池研究进展

热电材料是一种能够实现热能和电能直接相互转换的绿色环保型功能材料。近年来研究发现,薄膜热电材料及其器件有高的热电转换效率和实用性,具有重要的研究价值和市场实用价值。本文首先介绍国内外低温B-i Sb-Te系热电薄膜材料的研究现状,在阐述提高B-i Sb-Te系薄膜热电材料性能的方法、途径以及其应用的基础上,介绍了热电薄膜制备技术方面的关键科学问题所在。其次介绍了国内外薄膜温差电池的研究进展和发展趋势。在总结薄膜热电材料及其器件发展历史和分析热电理论的基础上,阐述了薄膜温差电池方面的研究进展和关键技术所在。     

High Electrical Conductivity of Single Metal–Organic Chains

Molecular wires are essential components for future nanoscale electronics. However, the preparation of individual long conductive molecules is still a challenge. MMX metal–organic polymers are quasi‐1D sequences of single halide atoms (X) bridging subunits with two metal ions (MM) connected by organic ligands. They are excellent electrical conductors as bulk macroscopic crystals and as nanoribbons. However, according to theoretical calculations, the electrical conductance found in the experiments should be even higher. Here, a novel and simple drop‐casting procedure to isolate bundles of few to single MMX chains is demonstrated. Furthermore, an exponential dependence of the electrical resistance of one or two MMX chains as a function of their length that does not agree with predictions based on their theoretical band structure is reported. This dependence is attributed to strong Anderson localization originated by structural defects. Theoretical modeling confirms that the current is limited by structural defects, mainly vacancies of iodine atoms, through which the current is constrained to flow. Nevertheless, measurable electrical transport along distances beyond 250 nm surpasses that of all other molecular wires reported so far. This work places in perspective the role of defects in 1D wires and their importance for molecular electronics.     

Diffused Lattice Vibration and Ultralow Thermal Conductivity in the Binary Ln–Nb–O Oxide System

In the pursuit of low thermal conductivity materials for thermal management, one always tries to increase the material entropy by increasing the number of components in the materials to scatter heat‐carrying phonons. However, it also drastically increases the technological complexity to synthesize materials with the target complex composition. Here, a material family is presented with simple composition Ln₃NbO₇, which only contains binary oxides of Ln₂O₃ (Ln = Dy, Er, Y, Yb) and Nb₂O₅. The thermal conductivities approach the theoretical minimum limit, where the large chemical inhomogeneity due to the charge disorder and fluctuation of bonding length in Ln₃NbO₇ plays a major role. Despite the simple composition, Ln₃NbO₇ demonstrates an unprecedentedly high scattering rate of vibration states, as confirmed by the highest elastic constant/thermal conductivity ratio, as well as the diffused wavevector‐frequency dispersion. In contrast to the conventional wisdom that low thermal conductivity materials should be explored in the pool of “complex” multiple‐component materials, this work points out an avenue to look into materials with simple composition but large internal chemical inhomogeneity, which would be of both scientific and technological significance in the fields of thermal barrier coating, thermoelectric materials, etc.