New Material for Future Optoelectronics
Central to our electronics are diodes, which only allow electrical currents to travel in one direction, and typically these are produced by doping a semiconductor. As this is not a reversible process, once a material is doped to have excess positive or negative charges, it will remain like that. Researchers at MIT though have recently found a material that can be made to switch between p-type and n-type without doping.
The material is tungsten diselenide (WSe2) and is just a molecule thick. This thinness enables it and similar materials to interact with both light and electricity, which is necessary for future optoelectronics. What the MIT researchers found is that by placing a sheet of WSe2 next to a metal electrode, it was possible to change the electrical doping of the material by tuning the voltage in the electrode. From this the researchers then built a device in which one sheet of WSe2 was doped to be half p-type and half n-type, thus creating a diode, near that of an ideal diode. With such a diode it should be possible to create photodetectors, photovoltaic cells, and LEDs, which the MIT researchers have demonstrated.
As important as its potential applications, it is already known how to produce large pieces of WSe2, and because of the extreme thinness of WSe2, it will not be very expensive, despite selenium's rarity. Also there are two other related papers reporting similar results from two different groups.