Tungsten diselenide
Identifiers | |
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12067-46-8 | |
EC Number | 235-078-7 |
Jmol 3D model | Interactive image |
PubChem | 82910 |
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Properties | |
Se2W | |
Molar mass | 341.76 g/mol |
Appearance | grey to black solid |
Odor | odorless |
Density | 9.32 g/cm3[1] |
Melting point | > 1200 °C |
insoluble | |
Structure | |
hP6, space group P6 3/mmc, No 194[1] |
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a = 0.3297 nm, c = 1.2982 nm
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Trigonal prismatic (WIV) Pyramidal (Se2−) |
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Vapor pressure | {{{value}}} |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references | |
Tungsten diselenide is an inorganic compound with the formula WSe2.[2] The compound adopts a hexagonal crystalline structure similar to molybdenum disulfide. Every tungsten atom is covalently bonded to six selenium ligands in a trigonal prismatic coordination sphere while each selenium is bonded to three tungsten atoms in a pyramidal geometry. The tungsten–selenium bond has a length of 0.2526 nm, and the distance between selenium atoms is 0.334 nm.[3] Layers stack together via van der Waals interactions. WSe2 is a very stable semiconductor in the group-VI transition metal dichalcogenides.
Synthesis
Heating thin films of tungsten under pressure from gaseous selenium and high temperatures (>800 K) using the sputter deposition technique leads to the films crystallizing in hexagonal structures with the correct stoichiometric ratio.[4]
- W + 2 Se → WSe2
Potential applications
Transition metal dichalcogenides are semiconductors with potential applications in solar cells. WSe
2 has a band-gap of ~1.35 eV with a temperature dependence of -4.6×10−4 eV/K.[6] WSe
2 photoelectrodes are stable in both acidic and basic conditions, making them potentially useful in electrochemical solar cells.[7][8][9]
The properties of WSe
2 monolayers differ from those of the bulk state, as is typical for semiconductors. Mechanically exfoliated monolayers of WSe
2 are transparent photovoltaic materials with LED properties.[10] The resulting solar cells pass 95 percent of the incident light, with one tenth of the remaining five percent converted into electrical power.[11][12] The material can be changed from p-type to n-type by changing the voltage of an adjacent metal electrode from positive to negative, allowing devices made from it to have tunable bandgaps. As a result, it may enable LEDs of any color to be made from a single material.[13]
References
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- ↑ Xia, F.; Wang, H.; Xiao, D.; Dubey, M.; Ramasubramaniam, A., "Two-dimensional material nanophotonics", arXiv.org, e-Print Arch., Condens. Matter 2014, 1-23, arXiv:1410.3882v1411.
- ↑ Zhang, X.; Qiao, X.-F.; Shi, W.; Wu, J.-B.; Jiang, D.-S.; Tan, P.-H., "Phonon and Raman scattering of two-dimensional transition metal dichalcogenides from monolayer, multilayer to bulk material", Chemical Society Reviews 2015, volume 44, 2757-2785. doi:10.1039/C4CS00282B
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
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- Tungsten compounds
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