Graphene is being used to produce a low-voltage LED

Low voltage LED

Graphene and other 2D materials are being used to produce a low-voltage LED which could potentially revolutionise energy efficiency in light emitting devices.

Light emitting diodes (LED) were first produced in 1962. Since then, they are used in virtually every electronic device. LED voltage is usually quite high due to the voltage having to be either equal to or higher than the band gap energy per electron charge.

Recent studies conducted at the The University of ManchesterUniversity of Warsaw, the High Magnetic Field Laboratory in Grenoble and the National Institute for Materials Science in Japan, has resulted in a more efficent, lower voltage LED being developed.

By using atomically thin combined semiconductors, researchers were able to produce an LED that uses a far lower voltage. These findings could potentially lead to devices consuming far less energy.

Researchers created new heterostructures, a structure previously used in semiconductors, by holding two atomically thin structures, such as graphene, by using weak Van der Waals forces.

With hundreds of combinations of these Van der Waal heterostructures could potentially hold the key to more efficient materials and devices, especially optoelectric devices.

Dr Aleksey Kozikov of the National Graphene Institute at Manchester University, said: “It is fascinating how adding just one atomically thin material can change properties of a device so dramatically. This is the power of van der Waals heterostructures in action.”

Dr Kozikov worked with Professor Kostya Novoselov and Professor Marek Potemski to publish their findings from this research. The findings highlight that researchers bound electrons to the holes in different dichalcogenides in transitional metals.

As a result of their research, charge carriers who’s energy was originally too low to over come the materials band gap, can now cross the potential barrier, recombine and then emit light.

the commonly used 2D material, graphene, was used to electrically inject charge carriers through hexagonal boron nitride stacked in a heterostructure into Molybdenum disulphide and Tungsten diselenide. This injection allows for LED tuning from a normal operation to a low-voltage operation.

The first author of the study was Dr. Johannes Binder from the University of Warsaw. He said: “When we started measuring the first MoS2/WSe2 devices we were really surprised to observe emission at such low applied voltages. This upconverted emission impressively shows the importance of Auger processes for interlayer excitons in van der Waals heterostructures. Our findings shed more light on the physics in the largely unexplored high carrier density regime, which is crucial for optoelectronic applications as well as for fundamental phenomena like interlayer exciton condensation.”

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