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9 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Cu2Se by Materials Project

Cu2Se crystallizes in the cubic F-43m space group. The structure is three-dimensional. there are two inequivalent Cu1+ sites. In the first Cu1+ site, Cu1+ is bonded in a 10-coordinate geometry to four equivalent Cu1+ and six equivalent Se2- atoms. All Cu–Cu bond lengths are 2.50 Å. All Cu–Se bond lengths are 2.89 Å. In the second Cu1+ site, Cu1+ is bonded to four equivalent Cu1+ and four equivalent Se2- atoms to form edge-sharing CuCu4Se4 tetrahedra. All Cu–Se bond lengths are 2.50 Å. Se2- is bonded in a 4-coordinate geometry to ten Cu1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cu2Se by Materials Project

Cu2Se crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are eight inequivalent Cu1+ sites. In the first Cu1+ site, Cu1+ is bonded in a 4-coordinate geometry to one Cu1+ and four Se2- atoms. The Cu–Cu bond length is 2.44 Å. There are a spread of Cu–Se bond distances ranging from 2.48–2.65 Å. In the second Cu1+ site, Cu1+ is bonded to four Se2- atoms to form distorted corner-sharing CuSe4 tetrahedra. There are a spread of Cu–Se bond distances ranging from 2.39–2.65 Å. In the third Cu1+ site, Cu1+ is bonded to four Se2- atoms to form distorted corner-sharing CuSe4 tetrahedra. There are a spread of Cu–Se bond distances ranging from 2.39–2.68 Å. In the fourth Cu1+ site, Cu1+ is bonded in a trigonal planar geometry to three Se2- atoms. There are one shorter (2.39 Å) and two longer (2.42 Å) Cu–Se bond lengths. In the fifth Cu1+ site, Cu1+ is bonded to two equivalent Cu1+ and four Se2- atoms to form distorted CuCu2Se4 tetrahedra that share corners with seven CuSe4 tetrahedra and edges with two equivalent CuCu2Se4 tetrahedra. Both Cu–Cu bond lengths are 2.50 Å. There are a spread of Cu–Se bond distances ranging from 2.45–2.60 Å. In the sixth Cu1+ site, Cu1+ is bonded in a trigonal planar geometry to three Se2- atoms. There are one shorter (2.40 Å) and two longer (2.41 Å) Cu–Se bond lengths. In the seventh Cu1+ site, Cu1+ is bonded in a 9-coordinate geometry to three Cu1+ and six Se2- atoms. There are a spread of Cu–Se bond distances ranging from 2.86–3.01 Å. In the eighth Cu1+ site, Cu1+ is bonded in a trigonal planar geometry to three Se2- atoms. There are one shorter (2.41 Å) and two longer (2.43 Å) Cu–Se bond lengths. There are four inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 8-coordinate geometry to eight Cu1+ atoms. In the second Se2- site, Se2- is bonded to seven Cu1+ atoms to form a mixture of distorted edge and corner-sharing SeCu7 hexagonal pyramids. In the third Se2- site, Se2- is bonded in a 7-coordinate geometry to seven Cu1+ atoms. In the fourth Se2- site, Se2- is bonded in a 6-coordinate geometry to nine Cu1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cu2Se by Materials Project

Cu2Se crystallizes in the orthorhombic Pmn2_1 space group. The structure is three-dimensional. there are two inequivalent Cu1+ sites. In the first Cu1+ site, Cu1+ is bonded in a distorted trigonal planar geometry to three equivalent Se2- atoms. There are one shorter (2.41 Å) and two longer (2.45 Å) Cu–Se bond lengths. In the second Cu1+ site, Cu1+ is bonded to four equivalent Se2- atoms to form a mixture of corner and edge-sharing CuSe4 tetrahedra. There are a spread of Cu–Se bond distances ranging from 2.43–2.56 Å. Se2- is bonded in a 7-coordinate geometry to seven Cu1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cu2Se by Materials Project

Cu2Se crystallizes in the tetragonal P4_32_12 space group. The structure is three-dimensional. Cu1+ is bonded in a trigonal planar geometry to three equivalent Se2- atoms. There are one shorter (2.41 Å) and two longer (2.42 Å) Cu–Se bond lengths. Se2- is bonded to six equivalent Cu1+ atoms to form distorted corner-sharing SeCu6 pentagonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Hierarchical Hybrid Multifunctional Materials through Interface Engineering

This project focuses on the development of stimuli-responsive hybrid multifunctional materials. We place emphasis on the design, synthesis, structural characterization, evaluation of functional properties (electronic, thermal and optical) of several (1-x)Cu 2 Se/(x)WBGS hierarchical bulk composites between Cu 2 Se, a narrow band gap semiconductor (NBGS), with a range of wider band gap semiconductors (WBGS) such as CuMSe 2 (M = Al, Ga, In, Fe, Cr) and Cu 4 TiSe 4 . Cu2Se is a well-studied NBGS with excellent thermoelectric properties (high electrical conductivity, large thermopower, etc.) while CuMSe 2 and Cu 4 TiSe 4 are high performance solar absorber materials (large band gap, large absorption coefficient, etc.). Our primary objectives are (i) to demonstrate the ability to integrate dissimilar functional properties such as large optical absorption coefficient and high electronic conductivity, within (1-x)Cu 2 Se/(x)WBGS composite; and (ii) to establish the correlation between the hierarchical structural entanglement of Cu 2 Se with WBGS (CuMSe 2 or Cu 4 TiSe 4 ) phase, the interactions between native electronic defects within the coexisting phases in the resulting (1-x)Cu 2 Se/(x)WBGS bulk composites , and the impacts on their electronic conductivity, thermal transport and optical properties.

36 MATERIALS SCIENCE↗
NASA NTRS1992

Room temperature synthesis of copper indium diselenide in non-aqueous solution using an organoindium reagent

A novel two-phase synthesis of CuInSe2 at 25 C from Cu2Se and Cp3In in 4-methylpyridine has been discovered. Characterization of the material produced shows it to be platelet-shaped crystallites with an average particle size of 10 microns, less than 2 percent C and H, with a small amount of unidentified crystalline impurity. The results demonstrate that it is possible to produce from solution a material that is ordinarily synthesized in bulk or films at much higher temperatures or using extraneous reagents and/or electrons. The use of a solid-state reagent as a starting material which is converted to another solid-state compound by an organometallic reagent has tremendous potential to produce precursors for a wide range of solid-state materials of interest to the electronics, defense, and aerospace communities.

Hepp, Aloysius F.↗
NASA NTRS1994

Room-temperature synthesis of CuInQ2 (Q = S or Se) in non-aqueous solution using an organoindium reagent

We have discovered a novel two-phase synthesis of CuInSe2 at 25 deg C from Cu2Se and (C5H5)3In in 4-methylpyridine (4-MePy). An analogous reaction to produce CuInS2 must be run at 140 deg C in refluxing 4-MePy in the presence of 2-mercaptopyridine. Microscopy of CuInSe2 produced at 25 deg C shows it to be platelet-shaped crystallites with an approximate particle size of 10 microns, less than 2 percent C and H, with a small amount of unidentified crystalline impurity. Our results demonstrate that it is possible to produce from solution a material that is ordinarily synthesized in bulk or films at much higher temperatures or using extraneous reagents and/or electrons.

Hepp, Aloysius F.↗
DOE OSTI2022

Weak Electron–Phonon Coupling and Enhanced Thermoelectric Performance in n-type PbTe–Cu 2 Se via Dynamic Phase Conversion

This study investigates Ga-doped n-type PbTe thermoelectric materials and the dynamic phase conversion process of the second phases via Cu 2 Se alloying. Introducing Cu 2 Se enhances its electrical transport properties while reducing its lattice thermal conductivity (κlat) via weak electron–phonon coupling. Additionally, Cu 2 Te and CuGa(Te/Se) 2 (tetragonal phase) nanocrystals precipitate during the alloying process, resulting in Te vacancies and interstitial Cu in the PbTe matrix. At room temperature, Te vacancies and interstitial Cu atoms serve as n-type dopants, increasing the carrier concentration and electrical conductivity from ≈1.18 × 10 19 cm –3 and ≈1870 S cm –1 to ≈2.26 × 10 19 cm –3 and ≈3029 S cm –1 , respectively. With increasing temperature, the sample exhibits a dynamic change in Cu 2 Te content and the generation of a new phase of CuGa(Te/Se) 2 (cubic phase), strengthening the phonon scattering and obtaining an ultralow k lat . Pb 0.975 Ga 0.025 Te-3%CuSe exhibits a maximum figure of merit of ≈1.63 at 823 K, making it promising for intermediate-temperature device applications.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Improved thermoelectric performance of α- and β- Cu 2 Se through suppression of hole density using extrinsic copper vacancies

Modulating Cu + ion disorder in Cu 2 Se can enable control over the polymorphism and the carrier density leading to enhanced thermoelectric properties for both α- and β-Cu 2 Se. Here we report that the incorporation of Cr 3+ into the Cu 2 Se crystal lattice facilitates the stabilization of α-Cu 2 Se at 300 K leading to a large (~140%) reduction in the carrier density both below and above the phase transition. This is attributed to the reduction in the density of intrinsic copper interstitials (Cu$^{•}_{i}$) within the Cu (2-δ-λ) (Cr$^{··}_{Cu}$)λ(V$^{'}_{Cu}$)δ(Cu$^{π}_{i}$) δ-2λ (h • ) δ-2λ Se crystal lattice. Such optimization of the carrier density led to a large (63%) increase in the thermopower and a drastic (46%) reduction in the total thermal conductivity for both α- and β-Cu 2 Se matrices. Consequently, a significant enhancement of the thermoelectric performance is observed in the entire temperature range from 300 K to 773 K. This results in high average ZT values for both α-Cu 2 Se (ZT ave = 0.60) and β-Cu 2 Se (ZT ave = 0.97), which paves the way for both near room temperature and high temperatures applications. Furthermore, this work provides a new approach to optimize the thermoelectric performance of Cu 2 Se-based materials by leveraging the interaction between mobile intrinsic Cu$^{·}_{i}$ and extrinsic V$^{'}_{Cu}$ to suppress the hole density.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗