Graphene LED Bulb

Dr.SS Verma, Dept. of Physics, SLIET, Longowal (Punjab)

2020-03-13 13:45:27



Use of Light emitting diodes (LED) not in lighting industry but in many other applications from health to entertainment has revolutionized the life of people. Similarly graphene with its different exotic properties has emerged as wonder material of the century.  Graphene is a modified version of carbon whose invention has already bagged Physics Noble Prize in 2010. It is reported to be around 100 times stronger than steel by weight and is hugely efficient at conducting both heat and electricity. It is light, durable, and almost transparent. A  number of applications of graphene has emerged recently in industry, particularly in electronics, energy storage, and photovoltaics. Companies all over the world are working extensively on graphene-related products and research, including water-purification membranes, coatings to protect steel and masonry, and enhancements to batteries for better performance and longer life.  Combination of these two inventions into one has resulted in a graphene LED bulb which is simply an LED light bulb with its filament coated in graphene and the bulb is reported to be 10% more efficient and cheaper than regular LED light bulbs. LED lights are the latest technology in the evolving world of lighting and electronics. The new lamp was developed at the University of Manchester, in the U.K., where graphene was first discovered more than a decade ago.

LED lighting

A revolution in energy-efficient, environmentally-sound, and powerfully-flexible lighting is coming to businesses and homes in terms of a future with widespread use of light emitting diodes (LEDs), which offer a number of obvious and subtle advantages over traditional light bulbs. There are tremendous opportunities that open up with LED lighting. LEDs are more rugged, resembling something closer to hard plastic than thin glass. They are also more environmentally sound, since their manufacture does not require toxic substances such as mercury. LED lights provide significant energy savings. They can be 2,000 percent more efficient than conventional light bulbs and 500 percent more efficient than compact fluorescent bulbs. All of these advantages make LEDs a good replacement light source and this is why there has been a tremendous recent expansion of the LED industry, which is growing by double-digit rates. Scientists and engineers envision a day when light switches give way to light switchboards that control not only the brightness of a light, but its color temperature and hue. Light spectra could be custom-tailored for all wavelengths, accurately matching the sun's light qualities and vary these characteristics according to the time of day, for instance. This could revolutionize indoor agriculture and help night-shift workers and people who are jet-lagged. The use of polarized light from LEDs could also improve computer displays and lower the glare from car headlights.

LED revolution

Light-emitting diodes, are semiconductor devices that produce visible light when electric current passes through them. They have been around for years-lighting digital clocks, computer screens and traffic signals-but were not seen as a traditional source of light until Netherlands-based Lemnis Lighting became the first company in the world to commercially manufacture LED bulbs in 2006. Most developed countries such as the US and Britain have made a big switch to LED bulbs. According to the US Department of Energy, "Widespread use of LED lighting has the greatest potential impact on energy savings in the US. By 2027, use of LEDs could save about 348 terawatt hours (compared to no-LED use) of electricity: This is the equivalent annual electrical output of 44 large electric power plants (1,000 megawatts each), and a total savings of more than $30 billion. In India, the first LED bulb was manufactured by NTL Electronics in 2009 based on the technology from Lemnis. In 2014, NLT acquired Lemnis and is one of the largest manufacturers of LED bulbs in the world. More than a dozen companies are also indigenously manufacturing LED bulbs in India today. This move is supported by the government of India and the aim is to replace all 77 crore incandescent bulbs sold in India with LEDs.

Graphene revolution

Graphene is an atomic-scale hexagonal lattice made of carbon atoms. It has been called a “wonder material” thanks to its many unique properties. It’s ultra-lightweight, highly elastic, extremely flexible and so thin (a single atom in thickness, or one million times narrower than the diameter of a human hair) as to be nearly transparent – and yet it’s 200 times stronger than steel and the most impermeable material ever discovered. It’s also an exceptional conductor of both heat and electricity. Here’s a list of some areas where this wonder material is being put to wondrous use: Creating ultra-fast computers, Building better batteries, Transforming transportation, Energizing electric vehicles, Weaving washable wearables, Constructing for sustainability, Preventing infection and reducing rejection, Solving the growing water crisis, Cleaning up oil spills, Turning surfaces into power sources, Aiding firefighting, Saving lives and  applications straight out of science-fiction: Flat lenses made from gold covered with graphene can control and bend light – making it theoretically possibility to produce an “invisibility cloak.”

Graphene LED Bulb

The first on-chip, visible-light source that uses “wonder material” graphene as a filament has been created by an international team of researchers. The team found that small strips of freely suspended graphene, attached to metal electrodes, can reach temperatures of up to 2800 K, allowing it to emit visible light. The research, while preliminary, opens up intriguing scientific questions, and possible applications of atomically thin, transparent, flexible displays and optical interconnects with electronic circuits. Generating light on the surface of a chip is key to developing fully integrated photonic circuits that would, in theory, use light to carry information. In many ways, the new light source functions much like an incandescent light bulb, which glows as its wire filament is heated to a high temperature via an electrical current. Among its other remarkable properties, graphene is known for its very high thermal conductivity, but this makes it hard to heat it to extreme temperatures. Indeed, if it retained its really high thermal conductivity, it would not be possible to heat the graphene until it glowed in the visible spectrum, because the heat would flow away continuously.

Luckily, graphene’s thermal conductivity drops dramatically at high temperatures because of a process called “Umklapp scattering”, in which phonons scatter off one another. While graphene is normally mounted on a substrate acts as a heat sink to stop it from reaching such high temperatures.  Further, the researchers have been able to attach reliable electrical contacts to suspended graphene.  Adding graphene to an LED bulb helps to dissipate heat – this makes them much brighter, meaning a lower wattage bulb will have the same effect as a traditional LED bulb – effectively reducing energy use for the same result. It is being reported that Graphene LED Bulbs will be more efficient, use less energy, and subsequently cost less money to run than their traditional counterparts. With the addition of graphene, LED lights are said to be able to last 10% longer. As LED lights already have longer life spans than similar fluorescent or incandescent light bulbs, this means that Graphene LED Bulbs will have super-long life spans, reducing not only the amount of money on purchasing light bulbs but the effort and time wasted in replacing them. On an industrial or commercial scale, Graphene LED Lighting could be wonderfully advantageous.

Science of graphene LED

Lying at the interface of the graphene oxide (GO) and reduced graphene oxide (rGO) is a special type of partially reduced GO that has optical, physical, and chemical properties that lie somewhere in between those of GO and rGO. The most important "blended" property of the interfacial layer is that it has a series of discrete energy levels, which ultimately allows for the emission of light at many different energies, or colors. The occurrence of this property is especially interesting because, on their own, neither GO nor rGO (or any other known form of graphene, for that matter) can emit any light at all. This is because neither material has the right size "bandgap," which is the gap between two energy bands that electrons must jump across to conduct electricity or emit light. While GO has an extremely large bandgap, rGO has a zero bandgap. Instead of having a bandgap somewhere in between GO and rGO, the partially reduced interfacial GO actually has many different intermediate bandgaps as a result of how the blending occurs—not as a smooth transition, but in the form of rGO nanoclusters embedded within the GO layer. Because these rGO nanoclusters are reduced to varying degrees at the interface, they exhibit variations in their energy levels and, consequently, in the color of emitted light. These energy levels can be easily modulated by changing the applied voltage or by chemical doping, which selectively stimulates a single color of luminescence and enables tuning of the LED's color. The researchers designed, fabricated, and tested graphene-based LEDs. Overall, the devices demonstrated good brightness but low efficiency, which they plan to improve. Another drawback of the current prototype is a very short emission lifetime of less than a minute or so in ambient conditions and about 2 hours in vacuum. The researchers attribute the short lifetime to oxidation in the air and predict that protective coatings may improve this area. Despite the room for improvement, the researchers expect the graphene-based LEDs to have encouraging commercial prospects due to several advantages, including their precise color tunability, compact structure, and straightforward fabrication.  The efficiency of the graphene LED could be improved further. One way to achieve this would be by using n-type (semiconductor) materials combined with graphene. The short lifetime could also be improved by vacuum sealing. Commercialization may be expected in a few years with simple and low-cost methods.

Scope of applications

The fact that this is the first observation of luminescence in a graphene-based system paves the way toward using graphene as a light source in future graphene-based photonic devices. A color-tunable LED has also been highly desired for high-quality LED displays and light fixtures. Because the color changes in response to certain chemicals, the devices could also have sensing applications.  Graphene-based, color-tunable LEDs can enable the realization of flexible display technologies that can cover the entire visible spectrum. Conventional LEDs only emit a fixed wavelength of light and thus display technologies require a mixture of red, green, and blue LEDs. If a graphene-based, color-tunable LED is used, a full-color and flexible display can be realized in a simple way. A wide range of consumer and medical electronics can benefit from such a technology.