2024 Author: Howard Calhoun | [email protected]. Last modified: 2023-12-17 10:16
With the advent of the world community to the concept of sustainable development, which implies the greening of the entire industry and the increase in the environmental awareness of the consumer, products that bear the label "organic" are attracting great interest and increasing demand. And organic LEDs are no exception. New technological solutions and new products invariably attract the attention of "advanced" consumers who keep pace with the times. What is it - organic light-emitting diodes, what are the principles of their work and prospects for use? This is the topic of this article.
Just a bit of history
The electroluminescent properties of organic materials were discovered in 1950 by the French physicist Andre Bernanoz. But it wasn't until 1987 that this discovery became a technological solution in the first OLED device manufactured by Kodak. And in 2000, three chemists at once - A. McDiarmid, H. Shirakawa and A. Heeger - were awarded the Nobel Prize for discoveries in the fieldthin-conducting polymers of organic origin. Only in 2008, the first OSRAM OLED lamp went on sale, of which only 25 copies were made at a price of 25,000 euros. Today, such lamps are offered by several companies at a price of 500 euros, and there are already several directions in OLED technologies: PHOLED, TOLED, FOLED and others that are understandable only to specialists.
Where is organic?
Oddly enough, but the use of the word "organic" in this context has nothing to do with products of animal or plant origin. Organic light emitting diodes, or OLED (from the English Organic Light Emitting Diode), is a semiconductor made of carbon material that generates radiation when an electric current passes through it. In their manufacture, organic chemistry products (carbon compounds) are used, which allows us to call them organic LEDs.
Design and composition
The device itself consists of four parts: base, anode, cathode, conductive and radiating layers. The base or substrate can be made of glass, plastic or metallized plates. The anode is indium oxide doped with tin. The conductive and radiating layers are layers of polymers and low molecular weight organic compounds. The cathode is made of aluminum, calcium or other metal.
Technology is not for physicists
Organic LEDs are based on the sandwich principle. Several thin layers of semiconductorsof organic origin are sandwiched between differently charged electrodes (positive and negative). And all this is located on the basis of a transparent material - glass or plastic (for example, flexible polyamide). When current passes through the electrodes, they form charged particles (quasiparticles and electrons). In the middle organic layer, these particles are concentrated and create high-energy excitation, which causes the emission of light of different colors by the organic layer. Thus, the active matrix on organic light-emitting diodes is precisely luminescent or phosphorescent organic layers.
Types of OLED arrays
OLED displays are divided into active-matrix and passive-matrix by the type of matrix. Active-matrix devices are controlled by thin-film field-effect transistors, which are located under the anode film. In passive-matrix, the image is formed at the intersection point of perpendicularly located anode and cathode strips, while the control is carried out from an external circuit. Based on this, there are three schemes for color OLED displays:
- With separate color emitters - three organic matrices emit three primary colors (blue, green and red) from which the image is formed.
- With three white emitters and special color filters.
- Blue emitters convert short wavelengths into long wavelengths of red and green.
Modern application
Today, OLED technologies are mainly used inhighly specialized developments. Holography and night vision devices, organic displays of car radios and digital cameras, phone screens and light sources, TVs and monitors - all this is the reality of OLED technologies.
OLED lifespan
All modern devices created using this technology sooner or later exhibit color burn-in. Even at the opening, the fragility of the radiation of organic light-emitting diodes was discovered. The service life of a device today is considered almost exhausted if the display brightness has decreased by 50%. Operation is stopped at this indicator of about 70%. But corporations' investments in these technologies are paying off - more often than not, consumers change outdated devices before they are close to the end of their service life.
The most the most
The largest OLED panel to date is the product of a joint project between OSRAM, Philips, Novaled, Fraunhoter IPMS. The panel size is 33 by 33 cm, the area of the active part is 828 sq. cm, and aperture - 76%. With a brightness of 1 thousand candelas per square meter, the flux of light particles is 25 lumens per watt. The largest Lumiotec panel on sale today is 15 by 15 centimeters and has a luminous flux of up to 60 lumens per watt, which is equal to one fluorescent light bulb. And Panasonic plans to launch a 128 lumens per watt OLED display by 2020. An American corporation competes with itDoE, which promises panels with up to 170 lumens per watt.
Prospects for OLED panels
Most existing designs today are prototypes. They are expensive, made in limited quantities, do not bend and are not yet effective enough. Large corporations have focused their activities on reducing the cost of the project, increasing the size and increasing productivity. Experts predict the mass appearance of this product with affordable prices on the world market by 2020.
OLED lighting
Organic LEDs in lighting are still in their infancy on the market. Mass production of this product has not yet been launched by any corporation. The price of such lamps is still quite high for the average consumer, and their brightness and life leave much to be desired. The $75 billion global market share of OLED lighting is a pretty small amount. The consumers of these products are not individuals, but other corporations that are engaged in the design of furniture and premises, as well as corporations in the automotive industry.
Pros and cons
Organic LEDs have both advantages and disadvantages. Among the first, their low power consumption and uniform distribution of light over the entire panel, high efficiency, environmental friendliness and soft light are indisputable. But the main advantage is the ability to give them flexibility and subtlety. And the shortcomings can be considered the short life of the diodes, the high cost and technological problems (organiccomponent oxidizes upon contact with water, which requires additional sealing). But corporations continue to invest in the development of these technologies, seeing them as the future of electronics.
How sustainable is this
OLED materials do not contain heavy metals and toxic elements such as mercury. They are easily recycled and do not require special collection and additional technological capacities for disposal. The iridium of OLED phosphorescent lamps is non-toxic and the amount is extremely small. Transportation of thin and light OLED panels requires fewer resources, which reduces costs and reduces the burden on the environment. For example, a 55-inch OLED TV is 4mm thick and weighs about 4-5 kilograms.
Fiction will become reality
Despite the skepticism of some experts, most are confident that OLED technology will be a major breakthrough in the 21st century. Fantastic projects will become real, namely:
- It is these technologies that will make it possible to create not an illusory, but quite realistic three-dimensional picture.
- Lighting everywhere will be replaced by OLED lamps.
- Transparent solar panels will appear.
- Flexible gadget monitors will fit in your pocket.
- Incredibly lightweight monitors with high color quality and a wide viewing angle will have an instant response, the smallest size and dimensions.
- The use of technology in the military industry is generally amazing.
- Hereglowing clothes have already appeared in designer collections.
But do not stop there - the motto of theoretical scientists and practitioners. Modern science has long been at a bifurcation point, when any discovery can turn the development of civilization into a completely unpredictable course. There are plenty of examples of such discoveries: this is the fullness of the vacuum, and Krasnikov's pipes, and even the discovery of organic compounds in deep space. Today the avant-garde of electronic gadgets is organic light-emitting diodes, but what tomorrow - who knows?
