Luminescence of silicon carbide crystals in electric current flow
History of LED starts from the beginning of the twentieth century. In 1907, English explorer Henry Round proposed technology, which LED was based on. He found a glow around the working detector contact. In the British Marconi Lab for the first time in the world history the luminescence in silicon carbide was recorded. Later in 1923, the Russian scientist Oleg Vladimirovich Losev found the connection for this phenomenon. In Nizhny Novgorod laboratory he observed the glow of silicon carbide crystals during the study of the phenomenon of radiative recombination. Losev was the first to prove the semiconductor electroluminescence, i.e. the emission of light when an electric current flows. It was the first step towards the creation of LEDs, but for a few decades this discovery had no practical application.
Industrial development of semiconductor lamps began only in 1951. In the United States a center for the development of "semiconductor lamps" was established, they were operating on the basis of "Losev effect", the center was headed by physicist and inventor Kurt Legovets. In 1955 - Rubin Braunstein from the Radio Corporation of America, told about the presence of the infrared radiation of gallium arsenide (GaAs) in combination with other semiconductor alloys. Braunstein observed infrared emission generated by simple diode structure based on gallium antimonide (GaSb), gallium arsenide , indium phosphide (InP) , and silicon - germanium alloy (SiGe) at room temperature.
In the 60s of the twentieth century the first LEDs from GaP were created, emitting a red and yellow- green light. The wavelength emitted by these devices was within the upper limit of perception of the human eye (500-600 nm), so for the indication purposes this yellow- green fluorescence was quite enough. Luminous efficacy of LEDs was about 1-2 lumens / watt. 1962 - University of Illinois in the United States, led by Nick Holonyak, created the first LEDs of industrial scale based on GaAsP / GaP structures. Nick Holonyak is considered to be the "father" of modern LEDs.
1968 - the first LED light for indicator Monsanto was created. The same year in USA Hewlett-Packard Company produced and released the world first LED advertising screen. It was a display with a very weak light flux, information on which was displayed only in red. Until the early 70s, visible and infrared LEDs were very expensive - up to $200 for a piece, and therefore had little practical application. In 1968, Monsanto Corporation established first serial production of visible LEDs, using gallium arsenide phosphide to produce red LED suitable for indicators.
LED with plastic shell-casing
In 70s of the twentieth century the rapid development of this industry begins. LEDs are improved in two directions at the same time: expanding the range of radiation and increase of flux. In addition, under the leadership of the Russian scientist Jaures Ivanovich Alferov multipass double heterostructures were developed, due to which the active recombination region was limited, increasing the external quantum efficiency. Heterostructures were offered and practically created, firstly based on GaAs and solid solutions of AlGaAs type, and then based on other semiconductor compounds, with the red part of the spectrum increase to 15% (the luminous efficiency up to 10 lm/ W) and infrared up to 30% or more. However, the importance of this discovery was recognized only in 2000. Jaures Ivanovich Alferov won the Nobel Prize. Also in 70s in the laboratories of IBM in the United States, blue diodes were created based on epitaxial GaN. But the life cycle of these LEDs at the time was very short.
1976 - Hewlett Packard Company developed and released LEDs based on aluminum gallium phosphide indium, of red- orange, yellow and yellow-green colours. Their luminous efficiency reached up to 30 lm / W (which is more than of an incandescent bulbs), and external quantum efficiency of 55 %. A little later, in the early 80s, scientists from Lomonosov Moscow State University Michail Vasilievich Chukichev and Gennady Vasilievich Saparin found bright luminescence of GaN sample parts, doped with zinc when exposed to the electron beam. At that time scientists did not succeed in understanding the cause of that phenomenon.
Since 1985, the light flux emitted by the LEDs increased to 10 lm and they started to be used as independent light elements. The problem of devices emitting in the blue color range, for a long time did not find its solution. Only on March 28, 1991 - Japanese company Nichia Chemical produced LEDs with the blue glow. This day can be considered as "Birthday" of blue LEDs. The parent of this invention was Japanese scientist Dr. Nakamura (Shuji Nakamyra). He managed to solve this problem by using a heterostructure based on indium gallium nitride InGaN. Due to this invention "RGB- circle" was closed. And it also became possible to connect the blue, yellow and red crystals in a triple-LED. This invention made it possible to produce radiation of any color. In 1993, Nichia Chemical Industries started mass production of blue LEDs based on GaN.
In the early 90s, the light output of LEDs reached 30 lm. 1997 - Fred Schubert produced the world first LED emitting white light. And already in 1998 in Russia the Covert - Lights company launched production of new generation of LEDs. By the end of the twentieth century, the world leading companies specialized in LED production ("Toyoda Gosei", "Hewlett Packard", "Nichia Chemical", "Cree") produced the tens of millions of blue and green LEDs a month. LED light output reaches up to 60 lumens / watt. Since that time, the LEDs become adequate alternative to incandescent lamps. Total number of LEDs produced in Russia was equal to 100 million pieces a year, and in the world up to tens of billions pieces.
Since 2000, "Nichia Chemical" and "Osram" companies began mass production of LEDs. The same year, "The Big Three " companies - "LumiLeds / Phillips", "Osram / Cree" and "GELcore / Uniroyal / GE" invested more than $ 70 million in research related to the development and application possibilities and production of LEDs. With the advent of LEDs the world advertising business rapidly began to develop.
By the middle of 2006 in the United States the number of electronic advertising "billboard " was equal to 200 pieces, and a year later this number doubled. Due to such advertising, there was a significant leap in all areas of production and sales.
By the end of 2006, LEDs have become an integral part of modern market, and the range of their application has expanded significantly. LEDs have been actively used for the production of mobile devices, all kinds of boards, screens and monitors, automotive lighting.
2008 - Bilkent University in Turkey reported achieving brightness luminous efficacy of 300 lumens of light in the visible region of the LED built on single crystal.
2009 - researchers from Cambridge University reported the launch of the process to grow gallium nitriding (GaN) for creating silicon-based LEDs. Production costs could be reduced by 90 % when using six-inch silicon wafers instead of two-inch sapphire wafers.
2010 - Nichia Corporation announced the development of experimental LEDs that due to several improvements in design and materials have made great progress in improving the efficiency of the light sources. One of developed LEDs at a current of 5 mA showed a record efficiency - 265 lm / W - which was very close to the theoretical limit for white LEDs, estimated by Japanese scientists as 260-300 lumens per watt. For comparison: conventional incandescent lamps give 13-17 lm / W, and fluorescent lamps - 60-90. The Japanese claim that the experiments will continue as opportunities for increasing the efficiency still exists. And although the current record LEDs samples are too expensive for mass production, in future the prices should come down - researchers from Nichia promise.
In 2010, the application of LEDs as an alternative to general lighting did not exceed 5 %, which was about $ 200 million. However, by 2011 this number has risen to almost $1 billion, and analysts predict that this number will increase every year.
Great LED - projects of the 21st century.
The biggest LED display in Tokyo
Mitsubishi Electric Corporation has built the world's largest display identical to three tennis courts, composed together. In Giant Screen Aurora Vision technology is applied - its surface consists of several million of bright LEDs. And repeating pattern of dots in three basic colors is selected in such a witty way that it gives the maximum resolution in color with a given number of LEDs. This recent innovation installed at the racecourse in Tokyo, has a height of 11.2 meters and a length of 66.4 meters, so its area is about 744 square meters. The cost of the screen is 28 million dollars. The customer was the Japanese Association of races JRA. Now fans have the possibility to watch the details of the competition in all its glory, and at the same time the details shot with multiple cameras.
In China, there are a lot of LEDs on the streets, and one of the brightest objects in the night time are a giant LED media wall in Beijing and Guangzhou TV Tower. Fine examples of combination of alternative energy and LED media carrier.
Also in Beijing a full-coloured LED screen of a huge size was built. Its launch was timed to coincide with the Summer Olympics in 2008. The screen is built into the canopy over the pedestrian area and is located at a height of 24 meters at the entrance to the city Megamall. A combination of five LED screens forms a continuous surface with dimensions of 250 x 30 m and has an area of 7500 m2. Truly a giant LED screen.
LED media wall in Beijing
Casinos in Macao (Special Administrative Region (SAR), China , known for dazzling lights and extravagant facilities, able to compete with Las Vegas. Grand Lisboa Hotel installed the intelligent lighting system, using programmed technology from Daktronics, which combines outdoor lighting effects,able to create and display the specified text messages, graphics, animation and video. The design of Grand Lisboa Hotel building was inspired by the yellow lotus flower, which is the official emblem of the Macao SAR. In the future, when the building is completed, it will be a high tower, which will rise from oval podium base. The oval podium itself, which is measured by 56 meters (184 feet) high and 189 meters (620 ft) wide, with a total area of approximately 10,609 square meters, fully lit by more than 59,000 ProPixel-LED lamps from Daktronics.
New York, famous Times Square. Screen of well-known "ABC" studio. Full-featured LED display, with an area of several square meters. This screen was mounted from 16 million LED elements.
One of the biggest screens that Chinese manufacturers produced for export, is considered to be LED - screen set up in the city of New Giza in Egypt. Its area is 1208 m2, 32 mm pitch screen. The screen is adapted to the hot climate and sandy wind. Its installation on the place took 1 month.
LED screen at the stadium of Atlanta Braves team
LED screen at the stadium of Atlanta Braves team became the world's largest outdoor screen with high resolution. Prior to its launch the leader in class HD of LED screens was the video screen of «Daktronics» company for Dolphins Stadium in Miami. It consists of two large display "ProStarV®» 1280 x 720 pixels each. This video monitor has an area of 636 m2.
LED screen "Viva Vision" in Las Vegas
In Las Vegas on Frimond street there is the world's largest LED screen "Viva Vision" valued at $17 million. For more than a year the workers were replacing nearly 2 million of conventional light bulbs by 12.5 million of LEDs. New LEDs are arranged at a height of 30 meters from the ground to improve the image quality by 900% compared to their predecessors, and as the result giving the picture quality comparable to HD TV image of the latest generation. The LG company – the creator of a unique LED screen, agreed to pay $ 2.25 million as sponsorship of the project, with the right to display advertising of its products in front of 16 million viewers each year. The length of the giant LED screen is 1500 feet (about 500 meters) and a width is 90 feet (30 meters). In order to realize how impressive are the dimensions of this display, you can compare it with an area of five football fields!
Where else, if not in UAE, can exist the skyscraper, one wall of which is a giant LED - screen? The project was named Podium, and the place for the construction was given in the large entertainment complex Dubailand. The LED wall with the height of 33 floors will have a slightly curved shape. To see the image will be possible at a distance of one mile.
Robots show "Dancing Cranes", Singapore
Singapore resort complex Resorts World Sentosa presented a grand show of robots "Dancing Cranes " with giant LED - screens, which can be seen from almost anywhere in the city.
The performance used two 30 -foot cranes, comparable to the height of a ten-floor house. It is the tallest in the world animatronic show, which involved "an animated electronics". Cranes are practically fully made of steel and weigh about 80 tons each. However, this does not deprive tap dancing from elegance and grace with which robots reproduce courtship dances of cranes.
Besides cranes, for creation of "Dancing Cranes " there were used LED screens, lighting, pyrotechnics and sound effects, as well as original music. The work on the preparation of the show took three years. Its author is the quadruple winner of «Emmy» Jeremy Railton, who created the stage design for concerts of world stars : Michael Jackson, Cher, Barbra Streisand and Diana Ross.
LED lighting in the 21st century is one of the most promising directions in small energy sector. The application of LED lights and lamps at industrial enterprises, warehouses, shopping centers, office centers, urban street lighting networks, motorways and in every house improves energy efficiency greatly. Today, LED lighting, of course, requires a serious investment of funds, but it is safe to say that the savings on electricity, which amounts to 90%, will quickly pay all the costs.
LED lighting is no longer a luxury, but an energy-efficient way to improve comfort and quality of life!