What is organic light-emitting diodes?

With the arrival of the world community in the concept of sustainable development, which implies the ecologization of the whole industry and the increase in the environmental awareness of the consumer, the products on which there is the designation "organic" cause great interest and increased demand. And organic light-emitting diodes did not become an 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 operation and the prospects for using it? This is the topic of this article.

Quite a bit of history

Electroluminescent properties of organic materials were discovered in 1950 by the French physicist Andre Bernanoz. But only in 1987 this discovery acquired a technological solution in the first OLED device manufactured by Kodak. And in 2000, just three chemists - A. McDiarmid, H. Sirakawa and A. Heger - were awarded the Nobel Prize for discoveries in the field of fine-conducting polymers of organic origin. Only in 2008, the first OLED-lamp from OSRAM company was on sale, only 25 of them were produced at a price of 25 thousand 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, which are clear only to specialists.

Where is the organic?

Strangely enough, the use of the word "organic" in this context has nothing to do with products of animal or vegetable origin. Organic light-emitting diodes, or OLED (from English Organic Light Emitting Diode), is a semiconductor made of carbon material that generates radiation when an electric current passes through it. When they are made, products of organic chemistry (carbon compounds) are used, which allows us to call them organic light-emitting diodes.

Structure and composition

The device itself consists of four parts: the base, the anode, the cathode, the conducting and radiating layers. The substrate or substrate can be made of glass, plastic or metallized plates. The anode is indium oxide doped with tin. Conducting and radiating layer are layers of polymers and low-molecular organic compounds. The cathode is made of aluminum, calcium or other metal.

The technology of work is not for physicists

Organic light-emitting diodes are arranged on the principle of a sandwich. Several thin layers of semiconductors of organic origin are sandwiched between differently charged electrodes (positive and negative). And all this is based on a transparent material - glass or plastic (for example, flexible polyamide). When the current passes through the electrodes, they form charged particles (quasiparticles and electrons). In the average organic layer these particles concentrate and create a high-energy excitation, which causes the emission of light of different colors by an organic layer. The active matrix on organic light-emitting diodes, thus, are luminescent or phosphorescent organic layers.

Types of organic light-emitting diodes

OLED-displays by type of matrix are divided into active-matrix and passive-matrix. Active-matrix devices are controlled by thin-film field-effect transistors, which are located under the anode film. In the passive-matrix image is formed at the point of intersection of perpendicularly located anode and cathode strips, while control is carried out from an external circuit. Based on this, there are three schemes of color OLED-displays:

• With separate color emitters - three organic matrices emit three base colors (blue, green and red), from which an image is formed.
• With three white emitters and special color filters.
• Blue emitters convert short waves into long waves of red and green colors.

Modern application

In our time, OLED-technologies are used mainly in highly specialized developments. Holography and night vision devices, organic displays of car radios and digital cameras, phone screens and light sources, TVs and monitors are all already realities of OLED technologies.

Service life of OLED devices

All modern devices created by this technology, sooner or later show a burning out of the brightness of the color. Even at the discovery, the fragility of the radiation of organic light-emitting diodes was found. The resource of operation of the device today is considered almost exhausted, if the brightness of the display has decreased by 50%. Operation at this indicator is stopped at about 70%. But corporate investments in the development of these technologies give their results - more often the consumer changes the out-of-date device even before it approaches the near end of the service life.

The best

The largest panel with organic LEDs for today is a product of a joint project of OSRAM, Philips, Novaled, Fraunhoter IPMS corporations. The size of the panel is 33 by 33 cm, the area of the active part is 828 square meters. Cm, and aperture - 76%. At a brightness of 1 thousand candelas per square meter, the flux of light particles is 25 lumens per watt. The largest panel of Lumiotec, sold today, has a size of 15 by 15 centimeters and a luminous flux of up to 60 lumens per watt, which is equal to one fluorescent light bulb. And by 2020 Panasonic Corporation plans to launch on the market a display on organic light-emitting diodes with a light flux of 128 lumens per watt. It competes with the American corporation DoE, which promises panels with a flow of up to 170 lumens per watt.

Outlook OLED panels

Most of the existing samples today are prototypes. They are expensive, manufactured in limited batches, do not bend and are not yet effective enough. Large corporations focused their activities on reducing the cost of the project, increasing size and increasing productivity. Experts predict the mass appearance of this product with affordable prices on the world market by 2020.

OLED lighting

Organic light-emitting diodes in lighting are still on the market in embryo. Mass production of this product has not yet been launched by any corporation. The price of such luminaires is still quite high for the average consumer, and the brightness and service life leave much to be desired. The $ 75 billion turnover in the global market, which accounts for the share of OLED lighting, is a fairly small amount. Consumers of this product are not individuals, but other corporations that are engaged in the design of furniture and premises, as well as the corporation of the automobile industry.

Advantages and disadvantages

Organic light-emitting diodes have advantages and disadvantages. Among the first, their low energy consumption and uniform distribution of light throughout the panel are undeniable, high efficiency, environmental friendliness and soft light. But the main advantage is the ability to give them flexibility and subtlety. And shortcomings can be considered the fragility of the service of diodes, high costs and technological problems (the organic component is oxidized by contact with water, which requires additional sealing). But corporations continue to invest in the development of these technologies, seeing in them the future of electronics.

Is it environmentally friendly?

OLED-materials do not contain heavy metals and toxic elements such as mercury. They are easily processed and do not require special collection and additional processing capacities for disposal. Iridium phosphorescent lamps on organic light-emitting diodes are non-toxic, and its quantity is extremely small. Transportation of thin and light OLED-panels requires less resources, which reduces costs and reduces the burden on the environment. For example, a TV with an OLED monitor with a diagonal of 55 inches has a thickness of 4 mm, and weighs about 4-5 kilograms.

Sci-Fi becomes a reality

Despite the skepticism of some experts, most believe that OLED technologies 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 a real three-dimensional picture.
• Lighting everywhere will replace OLED-lamps.
• Transparent solar panels will appear.
• Flexible monitors gadgets can be accommodated in your pocket.
• Incredibly light monitors with high color quality and a wide viewing angle will have instant response, minimum size and dimensions.
• The use of technology in the military industry in general is amazing.
• But the luminous clothing has already appeared in designer collections.

But do not dwell on what has been achieved - the motto of theoretical scientists and practitioners. Modern science has long been at the point of bifurcation, when any discovery can turn the development of civilization into a completely unpredictable channel. Examples of such discoveries abound: this is the fullness of the vacuum, and Krasnikov pipes, and even the discovery of organic compounds in deep space. Today, the avant-garde of electronic gadgets are organic LEDs, and tomorrow - who knows?