Abstract Transition metal dichalcogenides (TMDs) are known for their layered structure and tunable functional properties. However, a unified understanding on other transition metal chalcogenides (i.e. M 2 X) is still lacking. Here, the relatively new class of copper-based chalcogenides Cu 2 X (X = Te, Se, S) is thoroughly reported. Cu 2 X are synthesized by an unusual vapor–liquid assisted growth on a Al 2 O 3 /Cu/W stack. Liquid copper plays a significant role in synthesizing these layered systems, and sapphire assists with lateral growth and exfoliation. Similar to traditional TMDs, thickness dependent phonon signatures are observed, and high-resolution atomic images reveal the single phase Cu 2 Te that prefers to grow in lattice-matched layers. Charge transport measurements indicate a metallic nature at room temperature with a transition to a semiconducting nature at low temperatures accompanied by a phase transition, in agreement with band structure calculations. These findings establish a fundamental understanding and thrust Cu 2 Te as a flexible candidate for wide applications from photovoltaics and sensors to nanoelectronics.
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Heterostructures of Cu 2−x S/Cu 2−x Te plasmonic semiconductors: disappearing and reappearing LSPR with anion exchange
Localized surface plasmon resonance (LSPR) of Cu 2− x S nanorods is quenched during the initial Cu 2− x S/Cu 2− x Te core/shell stage of anion exchange then returns as Cu 2− x Te progresses into the nanorod. Phase change within the core accounts for this behaviour illustrating the complexity emergent from anion exchange.
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- NSF-PAR ID:
- 10377378
- Date Published:
- Journal Name:
- Chemical Communications
- Volume:
- 58
- Issue:
- 70
- ISSN:
- 1359-7345
- Page Range / eLocation ID:
- 9810 to 9813
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract A series of copper thiospinel compounds, CuCo2S4‐
x Sex (x = 0, 0.2, 0.4, 0.6, 0.8), have been successfully synthesized by solid‐state reaction and their structure and magnetic properties have been studied. The Rietveld refinements of X‐ray diffractions indicate that both the lattice constants and the nearest‐neighbor Cu‐Cu distances increase with increasing selenium doping. A weakly antiferromagnetic transition occurring at about 4 K is observed in CuCo2S4. Two antiferromagnetic transitions at about 3.5 K and 6 K are observed in selenium‐doped samples, which suggest that the exchange couplings associated with Cu‐S(Se)‐Cu and Cu‐Se(S)‐Cu, respectively, are responsible for the two antiferromagnetic transitions. Detailed analysis of the experimental results further indicates that the nearest‐neighbor molecular field coefficient is comparable to the next‐neighbor molecular field coefficient. We propose a reasonable model to explain this phenomenon. -
The syntheses and crystal structures of two bimetallic molecular compounds, namely, bis[bis(6,6′-dimethyl-2,2′-bipyridine)copper(I)] hexafluoridozirconate(IV) 1.134-hydrate, [Cu(dmbpy) 2 ] 2 [ZrF 6 ]·1.134H 2 O (dmbpy = 6,6′-dimethyl-2,2′-bipyridyl, C 12 H 12 N 2 ), (I), and bis[bis(6,6′-dimethyl-2,2′-bipyridine)copper(I)] hexafluoridohafnate(IV) 0.671-hydrate, [Cu(dmbpy) 2 ] 2 [HfF 6 ]·0.671H 2 O, (II), are reported. Apart from a slight site occupany difference for the water molecule of crystallization, compounds (I) and (II) are isostructural, featuring isolated tetrahedral cations of copper(I) ions coordinated by two dmbpy ligands and centrosymmetric, octahedral anions of fluorinated early transition metals. The tetrahedral environments of the copper complexes are distorted owing to the steric effects of the dmbpy ligands. The extended structures are built up through Coulombic interactions between cations and anions and π–π stacking interactions between heterochiral Δ- and Λ-[Cu(dmbpy) 2 ] + complexes. A comparison between the title compounds and other [Cu(dmbpy) 2 ] + compounds with monovalent and bivalent anions reveals a significant influence of the cation-to-anion ratio on the resulting crystal packing architectures, providing insights for future crystal design of distorted tetrahedral copper compounds.more » « less
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To address critical energy issues in civic structures, we have developed a novel concept of optical thermal insulation (OTI) without relying on a conventional thermal intervention medium, such as air or argon, as often used in conventional window systems. We have synthesized the photothermal (PT) materials, such as the Fe 3 O 4 and Fe 3 O 4 @Cu 2− x S nanoparticles, that exhibit strong UV and near-infrared (NIR) absorptions but with good visible transparency. Upon coating the inner surface of the window glass with a PT film, under solar irradiation, the inner surface temperature rises due to the PT effect. Subsequently, the temperature difference, Δ T , is reduced between the single pane and room interior. This leads to lower the thermal loss through a window, reflected by the U -factor, resulting in considerable energy saving without double- or triple-glazing. Comparing with the Fe 3 O 4 coatings, Fe 3 O 4 @Cu 2− x S is spectrally characterized with a much stronger NIR absorbance, contributing to an increased PT efficiency under simulated solar irradiation (0.1 W/cm 2 ). PT experiments are carried out via both white light and monochromic NIR irradiations (785 nm). The parameters associated with the thermal performance of the PT films are calculated, including PT conversion efficiency, specific absorption rate (SAR), and U -factor. Based on the concept of OTI, we have reached an optimum U -factor of 1.46 W/m 2 K for a single pane, which is satisfactory to the DOE requirement (<1.7 W/m 2 K).more » « less
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Alkali halide postdeposition treatments (PDTs) have become a key tool to maximize efficiency in Cu(In
x Ga1−x )Se2(CIGS) photovoltaics. RbF PDTs have emerged as an alternative to the more common Na‐ and K‐based techniques. This study utilizes temperature‐dependent current–voltage (JVT ) measurements to study a unique RbF PDT performed in a S atmosphere. The samples are measured before and after 6 months in a desiccator to study device stability. Both samples contain Na and K which diffuse from the soda–lime glass substrate. A reference sample and a RbF + S PDT sample both show the development of a rear contact barrier after aging. The contact barrier is higher for the RbF + S PDT sample, leading to decreased current in forward bias. Series resistance is also higher in the RbF + S PDT device which leads to lower fill factor. However, after aging the reference sample has a larger decrease in open‐circuit voltage (V OC). Ideality factor measurements suggest Shockley–Read–Hall recombination dominates both samples.V OCversus temperature and a temperature‐dependent activation energy model are used to calculate diode activation energies for each sample condition. Both techniques produce similar values that indicate recombination primarily occurs within the bulk absorber.
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/D2CC01859D
