Lighting is one of the most energy consuming technologies in use in our world. During 2012, about 12 percent of total U.S. electricity consumption was used for lighting; estimates of global energy use for lighting reach as high as 25 percent of global electricity consumption. Incandescent lighting, the first major form of electrical lighting, revolutionized the world by increasing the number of hours in which a person could be productive every day. Many decades later, fluorescents and halogen bulbs would produce some improvements in energy efficiency and service life.
Right now, though, we’re starting to reap the benefits of an incredible revolution in electrical lighting. Any improvement to lighting technologies pales in comparison to the possibilities of light-emitting diodes, or LEDs. Incandescents, halogens and fluorescents spend energy generating either heat or gaseous discharge in addition to light. Currently, incandescent bulbs produce about 16 lumens per watt and fluorescents product about 70 lumens per watt. LEDs can produce about 300 lumens per watt, and efficiency improvements are still being pursued. An LED can also achieve a service life of 100,000 hours, compared to 1,000 for incandescents and 10,000 for fluorescents.
Since LED technology has been able to mature, it has inspired an impressive breadth of innovation in various fields. The implications for street lighting and desk lighting are clear, but LEDs have been discussed for use in color-changing wall panels for building interior aesthetics or even contact lenses, enabling a user to check e-mail or access apps through their contacts. Electronic contacts are a technology we’ve actually seen before in our Companies We Follow coverage of Johnson & Johnson.
Earlier this month, a trio of scientists was honored with the 2014 Nobel Prize for Physics for inventing a crucial aspect of LED technology that has greatly increased the practical nature of LEDs. Isamu Akasaki, Hiroshi Amano and Shuji Nakamura, all of Japan, were awarded the science prize for inventing blue LED lights in the early 1990s. Their story is one of innovation meeting a major challenge in technology development that had stymied scientists for decades. What the inventors have left us with is a tool that could make our world much more colorful while also drastically reducing energy consumption around the globe at the same time.
The Challenge of Blue LED Lighting
Modern science has been aware of the ability of certain semiconductor diode materials to give off light when a charge is applied for more than 100 years. The first recorded instance of a semiconductor material giving off light when a current was applied occurred in 1907, when Marconi Company employee Henry J. Round noted that raw silicon carbide and “other materials” would give off lights in various hues which included yellow, orange, green and blue. However, the practical application of LED lights in technology products would not begin in earnest until the 1950s.
The light-emitting diode is a semiconductor with multiple layers. The LED includes an n-type layer which is comprised of a material with a surplus of negative electrons, and a p-type layer which an insufficient number of electrons. Between the n-type and p-type layers there rests an active layer. When an electric charge is applied to the LED, negative electrons from the n-type layer and positive holes from the p-type layer rush into the active layer. When those electrons and holes recombine, light is formed. The color of the light that is created is dependent largely on the semiconductor materials used in the LED.
Red and green LEDs were not difficult to achieve once researchers set about to developing the applications of this technology. Beginning in the middle of the 20th Century, LEDs were being used mainly as power indicators in various appliances, although other practical uses were found in calculators and digital watches. However, widespread implementation of LEDs as a mainstream lighting solution required them to be able to generate the white light that could be produced by incandescent bulbs. To create white light, blue light, which had a short wavelength created by highly energetic protons, was required.
The increased application of LEDs through the use of white lighting solutions drove a great deal of research and development into the field of creating blue LED lights, but a series of challenges proved to be too great for most laboratories. Many researchers had pinpointed the use of gallium nitride as a likely semiconductor material for creating blue light. However, for decades, the high quality gallium nitride crystals necessary for the diodes couldn’t be created in laboratory settings. Also, gallium nitride is a naturally n-type material, making it difficult to create the p-type layer necessary to create the light-emitting diode.
Let There Be (Blue) Light
The obstacles on the path towards blue LED light technologies began to fall apart in 1986, when scientists Akasaki and Amano, both working at Nagoya University, were able to create the high-quality gallium nitride required to create semiconductor materials for producing blue light. The duo achieved this through a method of layering aluminum nitride over a sapphire substrate as a surface on top of which the gallium nitride would grow. By accident a few years later, the researchers noted that the gallium nitride material glowed with a more intense light when viewed through a scanning electron microscope. They weren’t aware at the time, but they had just overcome the issue in creating p-type layers from gallium nitride.
Working separately at Nichia Chemicals, located in the Japanese town of Tokushima on the island of Shikoku, Nakamura perfected some aspects of the gallium nitride production process involving the creation of gallium nitride by growing layers of the substance at varying temperatures. Nakamura was also able to explain why the scanning electron microscope improved light emission: the electron beam of the microscope removed hydrogen atoms from the p-type layer, making it more effective. To achieve this effect without the use of a scanning electron microscope, Nakamura was able to perfect a heating process for gallium nitride that was able to create an effective p-type layer by 1992.
The group was able to collaborate on other innovations within the field of blue LED technology. Using blue LEDs, the team also created a blue laser which has a very short wavelength and can be packed much tighter. As a result, blue light can transmit up to four times the data of an infrared beam. This technology has been incorporated into the Blu-ray data storage format, supporting the creation of digital optical disks which can playback super high-definition video.
The history of blue LED light also encompasses some intriguing stories in intellectual property rights. Shuji Nakamura, the third member of the group of laureates and the one working mostly solo at Nichia Chemicals, has spoken out for greater compensation for inventors at corporations as well as for stronger intellectual property rights. In August 2001, Nakamura filed suit against Nichia arguing for reasonable compensation for one patent protecting a chemical vapor deposition process used to produce blue LEDs and lasers; Nichia’s original compensation to Nakamura for a patent protecting a $400 million-per-year business was only $170. In 2004, Tokyo District Court found that Nakamura was entitled to $180 million in compensation from Nichia Chemicals for his invention. In January 2014, blue LED technologies patented by Boston University professor Theodore Moustakas were at the center of 25 lawsuits filed by the institution, most of which were settled through the licensing of patent rights through the university.
The Incredible Uses of LEDs in Our World
With the advent of blue LED lighting, it is now possible to create white light devices by combining blue light with red and green. As the Nobel Foundation points out in their background report on the 2014 physics laureates, “Incandescent light bulbs had lit the 20th century; the 21st century will be lit by LED lamps. The fact that LEDs could supplant all incandescents and fluorescents in lighting applications alone has major implications for energy efficiency in our world. In an LED bulb, about half of the electricity charging the diode is converted into light, whereas incandescent bulbs only convert about four percent of their charge into light.
Not only can LEDs greatly reduce the amount of electricity used in the developed world, they may also have a tremendous impact in bringing lighting to 1.5 billion people in underdeveloped areas without electrical grids; LEDs can be powered by solar energy collected in these areas. The ability to control the color of LED lighting by adjusting the levels of blue, green or red would also support the creation of light with a more natural appearance so as to follow our internal biological clocks. Computer control of LEDs can help them change color over time and closely follow natural light cycles to which we are accustomed.
These facts alone make blue LEDs a revolutionary technology, but there are many other applications than interior or street lighting which are being pursued. Along with the wallpaper and contact lenses we discussed in the intro to this article, LEDs have been successfully used to grow plants in greenhouse settings using artificial light. Without LEDs, we wouldn’t have much of the screen display technologies necessary for liquid crystal display (LCD) screens used in televisions, computers and smartphones. LEDs constructed to produce ultraviolet light could even be used to sterilize water by breaking down the DNA of bacteria, viruses and other microorganisms.
Innovation in the face of great odds always makes for a great story. The challenges overcome by the team of Nobel Prize laureates were massive but the trio was able to unlock the secrets to what may be one of the last great innovations of the 20th Century. As we head further into the 21st, look for LEDs to start replacing many of the lighting technologies you’ve been using, and don’t be surprised to learn that your food might be grown or your water might be sterilized thanks to this handy little diode.