Graphene May Help in Rapid Advancement of Optoelectronic Devices
Scientists from Massachusetts Institute of Technology have discovered an important and beneficial property of graphene. This property is related to optics and can open new ways of efficient energy harvesting from sunlight and superfast photo-sensors.
The researchers published this finding in the Journal of Science.
Graphene was discovered in 2004 and is made up of one atom thick layer of carbon. It has many unique properties. Graphene has "high mobility and optical transparency". It is not only a robust and flexible substance but also stable to environmental situations. However, up till now less work has been done in its use in optoelectronic devices.
Researchers have found that if light source such as laser is acted upon an object, whose surface is made up of graphene, the electrons of this got heat and remain hot for longer than the rest of the object. They worked by developing many, so-called, monolayer and bilayer p-n nanojunction devices and then measured the resultant photocurrent produced by each device using laser light of wavelength 850 nanometers. They found an increase in photocurrent as a result of an increase in the power of the laser. In this research, they were able to produce 5 mA/W, even at a decreased temperature, which is 6 times higher than any other optoelectronic devices made by using graphene.
They concluded “that nonlocal hot carrier transport, rather than the photovoltaic effect, dominates the intrinsic photoresponse in graphene”. They also hypothesized that this increase is the result of lacking of heat transfer by electrons to other materials as a result of poor coupling.
Research team called this property, of heating the electrons for a longer time at low, medium or high temperatures, as hot-carrier regime. This property is unusual as other materials exhibit this property at very cold temperatures.
In another research, scientists discovered the "photo-thermoelectric effects at a graphene interface junction".
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