Tungsten Diselenide (WSe2) Powder and Crystal

Bulk tungsten diselenide (WSe₂) has a high absorption coefficient, high photostability, and a band-gap of 1.2 eV. It is an indirect band-gap semiconducting material that can be both n- and p-doped. The ambipolar nature of WSe₂ makes it possible to create electronic devices that include p−n junctions or complementary logic circuits.

Tungsten diselenide single layers are composed of a layer of tungsten atoms positioned between two layers of selenium atoms, with each tungsten atom coordinating through strong covalent-ionic bonds to six selenium atoms in a trigonal prismatic geometry.  As occurs in graphene, black phosphorus and other TMDC materials, multilayer structures are stabilised by weak Van de Waal forces. These forces are strong enough to hold layers together, but weak enough to allow mechanical exfoliation.

Like WS₂ and other TMDCs, 2-dimensional layered tungsten diselenide (WSe₂) has a 2H (semiconducting) structure. This structure is the more stable form of the two hexagonal phases that exist in the naturally-occurring bulk-material forms. A 1T octahedral phase also exists - this is metallic in nature and is only associated with single layer films. Monolayer, few-layer nanosheet structures, and nanoparticles can be prepared by mechanical or chemical exfoliation. It has been demonstrated that the phase change from 2H to 1T can happen via chemical treatments, such as lithium-assisted intercalation of bulk crystals or powder by liquid exfoliation.

We supply low price tungsten diselenide in several different forms for a range of applications.

Tungsten Diselenide Powder

Can be used for preparation of tungsten diselenide nanoplates and ultrathin films

Available in quantities of 500 mg or 1 g

≥99.995% purity

From £220

Tungsten Diselenide Crystals by Size

Can be used to produce single or few-layer tungsten diselenide sheets via mechanical or liquid exfoliation

Small (≥10 mm²) or medium (≥25 mm²) crystals available*

≥99.999% purity

From £520

*Typical representative size, areas/dimensions may vary

Bulk single tungsten diselenide crystal is most commonly used as sources from which single or few-layer sheets can be obtained via either mechanical or liquid exfoliation. Single tungsten diselenide crystal or films produced from such crystals are suitable for study using atomic force microscopy or transmission electron microscopy

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Few-layer WSe₂ nanosheets and nanoparticles can also obtained from tungsten diselenide powder by liquid-exfoliation using  mixture of 30% of isopropanol in water. Ti and V intercalated WSe₂ create delocalized antiferromagnetism, while Cr, Mn, Fe, and Co exhibit localized ferromagnetism in WSe₂. Iron-series transition-metal atoms intercalated WSe₂ may have potential applications in spin electronics and quantum-information devices.

Key Product Data

• High purity tungsten diselenide powder and crystals
• Sold according to weight or size respectively
• Low price with free worldwide shipping on qualifying orders

Structure of Tungsten Diselenide 

Tungsten diselenide single layers are composed of a layer of tungsten atoms positioned between two layers of selenium atoms, with each tungsten atom coordinating through strong covalent-ionic bonds to six selenium atoms in a trigonal prismatic geometry.  As occurs in graphene, black phosphorus and other TMDC materials, multilayer structures are stabilised by weak Van de Waal forces. These forces are strong enough to hold layers together, but weak enough to allow mechanical exfoliation.

Like WS₂ and other TMDCs, 2-dimensional layered tungsten diselenide (WSe₂) has a 2H (semiconducting) structure. This structure is the more stable form of the two hexagonal phases that exist in the naturally-occurring bulk-material forms. A 1T octahedral phase also exists - this is metallic in nature and is only associated with single layer films. Monolayer, few-layer nanosheet structures, and nanoparticles can be prepared by mechanical or chemical exfoliation.

The 2H-WSe₂ phase has a hexagonal symmetry, with a trigonal prismatic metal coordination, where layers of selenium atoms are stacked directly above one another. The 1T-WSe₂ phase has a tetragonal symmetry, with an octahedral metal coordination, as the layers are offset from each other. It has been demonstrated that the phase change from 2H to 1T can happen via chemical treatments, such as lithium-assisted intercalation of bulk crystals or powder by liquid exfoliation.

Properties of Tungsten Diselenide

After exfoliation of tungsten Diselenide crystal or powder, tungsten Diselenide typically has the following properties:

• ‎2H Hexagonal (space group: P6_3/mmc)
• High absorption coefficient and high photostability
• 2H-WSe₂ is semiconducting and 1T-WSe₂ is metallic in nature
• Phase change from 2H to 1T can happen via chemical treatments

Applications of Tungsten Diselenide

Tungsten diselenide single crystal can be used to prepare monolayer and few-layer WSe₂ by mechanical or liquid exfoliation, and tungsten Diselenide powder is suitable for liquid chemical exfoliation to prepare WSe₂ nanosheets and nanoparticles down to few-layer films.

2H-WSe₂ nanosheets and particles play an important role in device applications such as transistors, photodetectors, light emitting diodes, photovoltaic solar cells, and in biomedical and photothermal therapies.

Monolayer or few-layer WS₂ films that are mechanically exfoliated from bulk WS₂ crystals have been explored for applications in FETs, electrochemical cells, thermoelectrics, sensors, and light-emitting diodes. The energy gap of WSe₂ (1.2 - 1.4 eV) makes it perfect for applications in photovoltaics and solar cells.

The 1T-WSe₂ phase is of particular interest for hydrogen evolution reactions (HER). Aside from that, exfoliated 2H-WSe₂ nanosheets and particles play an important role in device applications such as transistors, photodetectors, light emitting diodes, photovoltaic solar cells, and in biomedical and photothermal therapies.

Literature and Reviews

• Layer-dependent electronic structure of an atomically heavy two-dimensional dichalcogenide, P-C. Yeh et al., Phys. Rev. B 91, 041407 (2015); DOI: 10.1103/PhysRevB.91.041407.
• Strain-Induced Indirect to Direct Bandgap Transition in Multilayer WSe2,
  S. B. Desai et al., Nano Lett., 14 (8), 4592–4597 (2014); DOI: 10.1021/nl501638a.
• Large-Area Synthesis of Highly Crystalline WSe2 Monolayers and Device Applications, J. Huang et al., ACS Nano, 8 (1), 923–930 (2014); DOI: 10.1021/nn405719x.
• Preparation and Applications of Mechanically Exfoliated Single-Layer and Multilayer MoS2 and WSe2 Nanosheets, H. Li et al., Acc. Chem. Res., 47, 1067−1075 (2014); DIO: 10.1021/ar4002312.
• Large-area synthesis of monolayer WSe2 on a SiO2/Si substrate and its device applications, J. Huang et al., Nanoscale, 7, 4193 (2015); DOI: 10.1039/c4nr07045c.
• Dynamic tungsten diselenide nanomaterials: supramolecular assembly-induced structural transition over exfoliated two-dimensional nanosheets, A. Muhabie et al., Chem. Sci., 9, 5452 (2018); DOI: 10.1039/c8sc01778f.
• 2H - 1T phase transition and hydrogen evolution activity of MoS2, MoSe2, WS2 and WSe2 strongly depends on the MX2 composition, A. Ambrosi et al., Chem. Commun., 51, 8450 (2015); DOI: 10.1039/c5cc00803d.
• Self-assembled 2D WSe2 thin films for photoelectrochemical hydrogen production, X. Yu et al., Nat Commun 6, 7596 (2015); DOI: 10.1038/ncomms8596.
• Atomic-layer triangular WSe2 sheets: synthesis and layer-dependent photoluminescence property, K. Xu et al, Nanotechnology 24, 465705 (2013); doi:10.1088/0957-4484/24/46/465705.
• Solution-Phase Synthesis of Highly Conductive Tungsten Diselenide Nanosheets, P. D. Antunez et al., Chem. Mater., 25, 2385−2387 (2013); DIO: 10.1021/cm400790z.