Update in LED Technologies
In technical terms, LED’s are semiconductors that release photons when the applied voltage pushes electrons to jump to another state. For general terms, LED’s are simply tiny bulbs that emit light when people plug in the power.
Perhaps LED’s physical dominance makes for a better context and understanding: LED’s are found in virtually every household today, lighting up digital clocks displays to calculators, remote controls to keypad phones and even modern television screens.
Historians attempting to trace back to the first days of light-emitting diodes are often brought to the first days of semiconductor developments instead. In the 1960′s, scientists made semiconductor prototypes by doping pure materials with impurities and changing their polarity to either P-type or N-type. Then, through a combination of these materials, p/n junctions are formed with varying band gaps, which are the ancestors of today’s semiconductors.
What is the relationship between p/n junction and LED?
To be brief, N-type materials are those with more electrons (e-) and P-type materials are those with more holes (e+). When layered together, they form empty direct or indirect junctions. Scientists found that applying an electrical voltage across the junction will allow electrons to jump across the band gap to fill holes. Devices behaving in such a way were named “diodes.”
Where does “light emission” part come into play? The jumping of electrons from one state to another caused a fascinating effect, at least to the earliest semiconductor researchers; as electrons move across the p/n junction, they release energy in the form of photons. When a photon’s frequency reaches ~420 terahertz, it then becomes visible to the human eye as light. However, when the photo’s frequency goes beyond ~ 750 terahertz, it is hard to be detected or invisible to the human eye.http://arclightscope.com/wp-content/uploads/2012/08/LED-980034545.jpg
Who are these pioneering scientists?
The first people to marvel at this phenomenon was the scientist who first observed electroluminescence from silicon carbide light-emitting diodes back in 1907, Henry Joseph Round of Marconi Lab. In 1961, James R. Biard and Gary Pittman first found infrared emission from gallium arsenide and invented GaAs based LEDs. Isamu Akasaki is one of the pioneers in GaN based LED demonstration. In 1992, Akasaki reported the first GaN p-n junction LED. Shuji Nakamura and Hiroshi Amano had significant contribution to the development of GaN based LEDs. Akasaki, Nakamura and Amano shared Noble Prize in Physics in 2014 for their invention of efficient blue LEDs.
LED remains a futuristic lighting technology as it holds key advantages over traditional lighting:1. Lifetime LED’s last longer. An average compact fluorescent bulb has a lifetime of 8,000 hours; traditional incandescent bulb 1,000 hours. The LED tips this scale completely with 50,000 hours of lifetime (Actually, it was reported of up to ~ 100,000 hours in some reports), which calculates to 11 years of continuous operation.
2. Efficiency LED’s function better. Conventional incandescent bulbs are inefficient as an enormous amount of energy is lost through heat dissipation; they waste roughly 80% of the electrical energy. LED’s, on the other hand, don’t lose nearly as much heat and can thus convert 80% of the energy directly to light, improving efficiency multi-fold.
3. Durability LED’s withstand more. Unlike traditional glass bulbs that shatter easily, LED’s are enclosed with sturdy components highly resistant to shock, weather, and vandalism. For their extremely durable properties, many emergency lighting systems adopt LED standards in their design to operate under the roughest conditions.
4. Intoxicity LED’s are pro-environment. While conventional bulbs contain toxic materials like mercury which are harmful for the environment, LED’s are 100% toxic-free and recyclable. Switching to LED fixtures is an easy and effective way to go green daily.
5. Flexibility LED’s are advancing. LED’s are not tied to the inflexible design of conventional bulbs. Recent developments of LED’s are shifting them to a three-dimensional design with the ability to use organic, bendable material.
When it comes to moving LED forward in design and efficiency, scientists have been exploring new frontiers from semiconductors scaling to material science experiments. Two relevant developments in the field include nanowire LED and organic LED (OLED).
Nanowire LED is the one-dimensional approach to traditional LED’s. As suggested by name, one nanowire LED is made up of countless tightly-knit semiconductor nanowires fabricated across a single platform, with each acting like an individual LED. Growing these DNA-sized nanowires across a wafer can provide a seamless color spectrum to the naked eye, allowing researchers to produce any color desired, paving the way for enhanced LED screens, color-defining structures, and more.
Does rolling up an iPad sound too futuristic? It can be done with fully realized OLED technology. In a nutshell, organic LED (OLED) is fabricated by coating organic semicunductor films with conductive yet flexible organic materials such as soft plastic substrates. The result is a light-emitting diode with incredible thinness and flexibility, highly marketable for the consumer electronics industry.
Brighter LED’s with seamless spectrum; robust, diode-lit cellphone applications; nanowires in medical and environmental sensing; electronic books that look resemble traditional paperbacks in touch and feel; rubbery television sets, phones, and tablets; and so much more – these are only brushing the surface of unpredictable LED potential. However, one thing is certain: this superior next-generation illuminating technology will be much more than just a traditional lighting replacement; with expected success, LED technology will be applied to practically everything digital and thus completely transform people’s perception of the world.
Light-emitting diodes – 2 edition, by E. Fred Schubert, Cambridge University Press, 2010