This review captures the synthesis, assembly, properties, and applications of copper chalcogenide NCs, which have achieved significant research interest in the last decade due to their compositional and structural versatility. The outstanding functional properties of these materials stems from the relationship between their band structure and defect concentration, including charge carrier concentration and electronic conductivity character, which consequently affects their optoelectronic, optical, and plasmonic properties. This, combined with several metastable crystal phases and stoichiometries and the low energy of formation of defects, makes the reproducible synthesis of these materials, with tunable parameters, remarkable. Further to this, the review captures the progress of the hierarchical assembly of these NCs, which bridges the link between their discrete and collective properties. Their ubiquitous application set has cross-cut energy conversion (photovoltaics, photocatalysis, thermoelectrics), en...

Compound Copper Chalcogenide Nanocrystals

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Nanostructured thermoelectric materials: current research and future challenge

Over the past 10–15 years, there have been significant advances in the scientific understanding as well as in the performance of thermoelectric (TE) materials. TE materials can be incorporated into power generation devices that are designed to convert waste heat into useful electrical energy. These TE materials can also be used in solid-state refrigeration devices for cooling applications. The conversion of waste heat into electrical energy will certainly play a role in our current challenge for alternative energy technologies to reduce our dependence on fossil fuels and to reduce greenhouse gas emissions. This article provides an overview of the various TE phenomena and discusses some of the primary TE materials that are currently being investigated. Several of the key parameters and terminology are defined and discussed along with an overview of some of the current and emerging technologies. The phonon glass–electron crystal approach to new TE materials for developing new materials is presented along wi...

Thermoelectric Phenomena, Materials, and Applications

We review the field of multinary metal chalcogenide nanocrystals, which has gained strongly increasing interest in the quest for novel narrow band gap semiconductors. Small (2–4 nm) CuInS2 and CuInSe2 nanocrystals, for example, exhibit size dependent luminescence in the visible and near infrared range. Their quantum yield can exceed 50% after growth of a ZnS shell, which makes them appealing emitters for lighting, displaying and biological imaging applications. Cu2ZnSnS4 (CZTS) nanocrystals, on the other hand, can be used as solution processed absorbing materials in thin film solar cells showing high power conversion efficiencies (currently around 8–10%). These examples illustrate that multinary metal chalcogenide nanocrystals have high potential for replacing classical cadmium and lead chalcogenide quantum dots in many fields. We give an overview of the chemical synthesis methods of the different systems reported to date, classifying them according to the obtained crystal structure. Next, we discuss their photophysical properties and give a brief description of the main fields of application. Finally, we conclude by outlining current challenges and related future directions of this exponentially growing domain.

Ternary and quaternary metal chalcogenide nanocrystals: synthesis, properties and applications

The use to e of tetrafluoropropenes, particularly (HFO-1234) in a variety of applications, including refrigeration equipment, is disclosed. These materials are generally useful as refrigerants for heating and cooling, as blowing agents, as aerosol propellants, as solvent composition, and as fire extinguishing and suppressing agents.

Compositions containing fluorine substituted olefins

A new solution-based method to fabricate Cu2ZnSn(S,Se)4 (CZTSSe) thin films is presented. Binary and ternary chalcogenide nanoparticles were synthesized and used as precursors to form CZTSSe thin films. The composition of the CZTSSe films can be easily controlled by adjusting the ratio of the nanoparticles used. The effect of compositional adjustment on device performance is illustrated. Laboratory-scale photovoltaic cells with 8.5% total-area efficiency (or 9.6% active-area efficiency) were demonstrated without anti-reflective coatings. Material characterization data revealed the formation of a bilayer microstructure during thermal processing and suggested a path forward on device improvement.

High-efficiency solution-processed Cu2ZnSn(S,Se)4 thin-film solar cells prepared from binary and ternary nanoparticles.

Structural, electrical, and thermal transport properties of CoSb3 partially filled with indium are reported. Polycrystalline samples of InxCo4Sb12 (0 ≤ x ≤ 0.3) were prepared by solid-state reaction under a gas mixture of 5% H2 and 95% Ar. The solubility limit of the indium filling voids in CoSb3 was found to be close to 0.22. Synchrotron X-ray diffraction refinement of the x = 0.2 sample showed that the indium is located in the classic rattler site and has a substantially larger thermal factor than those of Co and Sb. The electrical resistivity, Seebeck coefficients, and thermal conductivity of the InxCo4Sb12 samples were measured in the temperature range of 300−600 K. All samples showed metal-like behavior, and the large negative Seebeck coefficients indicated n-type conduction. The thermal conductivity decreased with increasing temperature for all samples. A thermoelectric figure-of-merit (ZT) ≥ 1 (n-type) has been achieved when x ≥ 0.2 in InxCo4Sb12 at 575 K.

Thermoelectric Properties of Indium-Filled Skutterudites

This invention provides compositions useful for preparing films of CZTS and its selenium analogues on a coated substrate. This invention also provides processes for preparing films and coated substrates comprising CZTS/Se microparticles embedded in an inorganic matrix. This invention also provides processes for preparing photovoltaic cells comprising films of CZTS and its selenium analogues.

Semiconductor inks, films, coated substrates and methods of preparation

Methanol electrooxidation in a 0.5 M sulfuric acid electrolyte containing 1.0 M CH3OH was studied on 30% Pt/carbon and 30% PtRu/carbon (Pt/Ru = 1:1) catalysts using X-ray absorption spectroscopy (XAS). Absorption by Pt and Ru was measured at constant photon energy in the near edge region during linear potential sweeps of 10−50 mV/s between 0.01 and 1.36 V vs rhe. The absorption results were used to follow Pt and Ru oxidation and reduction under transient conditions as well as to monitor Ru dissolution. Both catalysts exhibited higher activity for methanol oxidation at high potential following multiple potential cycles. Correlation of XAS data with the potential sweeps indicates that Pt catalysts lose activity at high potentials due to Pt oxidation. The addition of Ru to Pt accelerates the rate of methanol oxidation at all potentials. Ru is more readily oxidized than Pt, but unlike Pt, its oxidation does not result in a decrease in catalytic activity. PtRu/carbon catalysts underwent significant changes dur...

H. David Rosenfeld

Papers

High-efficiency solution-processed Cu2ZnSn(S,Se)4 thin-film solar cells prepared from binary and ternary nanoparticles.

Thermoelectric Properties of Indium-Filled Skutterudites

Semiconductor inks, films, coated substrates and methods of preparation

In-situ X-ray absorption spectroscopy study of Pt and Ru chemistry during methanol electrooxidation.

Ultralow wear fluoropolymer composites: Nanoscale functionality from microscale fillers