2D Materials: Tungsten diselenide
A transition metal dichalcogenide, tungsten diselenide (WSe2) is a semiconductor whose properties as a two-dimensional material have recently become of interest. The crystal structure of this inorganic compound is hexagonal, with each tungsten atom bonded to six selenium atoms in a trigonal prismatic coordination sphere and each selenium atom bonded to three tungsten atoms in a pyramidal geometry.
Monolayers of WSe2 are transparent photovoltaic materials with LED properties, with potential applications in electrochemical solar cells. Devices made with this material have tunable bandgaps, capable of changing from p-type to n-type and back and enabling LEDs of any color to be made from a single material. Given that WSe2 is a 2D material, any LEDs made from it are much thinner than standard LEDs used in today’s electronics.
Finally, photovoltaic cells of WSe2 are so thin that 95 percent of incident light passes through them, but a tenth of the remaining five percent can be converted to electricity – a relatively high internal conversion efficiency. Researchers are considering using materials such as WSe2 in windows, allowing light to pass through while still collecting energy.
WSe2 is typically made by heating thin films of tungsten under pressure from gaseous selenium, using the sputter deposition technique.
Image sources: ( 3 )