Tungsten selenide is an inorganic compound that can absorb light like graphene. Its CAS No. is 12067-46-8; Molecular formula is WSe2; Molecular weight is 341.77. The light that WSe2 absorbs is used to generate electricity. WSe2 is a very stable semiconductor in the group-VI transition metal dichalcogenides.
Structure
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 atom is bonded to three tungsten atoms in a pyramidal geometry. Layers stack together via van der Waals interactions. 
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.
W + 2 Se → WSe2
Application
WSe2 photoelectrode is stable in both acidic and basic conditions, making it potentially useful in electrochemical solar cells.
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