Recent years have been moved to the display technology. We move from plasma to LCD, now the boom is for LED screens, while still gaining market began development of its replacement: the OLED.
By Beatriz Pineda *
As its acronym in English defines it, OLED (Organic Light Emitting Diode) is an organic light emitting diode that contains films of organic components (chemical components, in gaseous, liquid or solid form whose molecules contain carbon) that when stimulated electrically emits light by itself.
Such films, depending on the type of construction, may be formed of small molecules or polymers. The first are composed of at least two atoms while polymers or macromolecules are composed of structural units repeat.
One of the great advantages of OLEDs is that they can create sharper and brighter images, consuming less energy than conventional light-emitting diodes LED or liquid crystal displays.
A little history
Until a few years ago only to organic materials were considered as insulators, but in the years 50 laboratory tests showed that certain organic components could carry current.
In the same decade, the first observations of electroluminescence in organic materials were produced by A. Bernanose et al., At the Nancy University in France.
In 1977 Heeger, Mac Diarmid and Shirakawa discovered a high conductivity in iodine-doped polyacetylene, who later in the year 2000 were awarded the Nobel Prize in Chemistry for "the discovery and development of conductive polymers in organic".
The first diode device was reported in 1987 by Tang et al., Eastman Kodak Company who developed based on molecular devices bilayer films deposited vapor, consisting of a layer of hole transporting and emissive layer generating electroluminescence.
Finally in 1990 Burroughes JH et al., In the Cavendish Laboratory in Cambridge, they reported a high efficiency green light emitting polymers using sheets 100 nanometers thick.
The basic structure OLED is composed of several extremely thin layers of various materials. The 6 basic layers are described below:
This layer may be transparent glass or plastic and is responsible for supporting the device.
The anode extracts electrons (holes inserted) when a current flows through the device.
Void transport layer (HTL)
This layer is responsible for transport of gaps (or holes) from the anode.
Emission layer (EML)
When electrons and holes recombine, energy transfer molecules who emission layer emitting light excited the characteristic color of its component.
Electron transport layer (ETL)
Its function is very similar to that of the HTL layer and is responsible for transporting the electrons from the cathode.
The cathode may be transparent or not depending on the type of OLED, this injects electrons when a current flows through the device.
Passive matrix OLED (PMOLED)
In this type of OLED cathode and anode they are formed by perpendicular strips. Since the organic layer is between said stripes, the light is emitted at intersections (pixels), by applying voltage in the horizontal and vertical matrix points.
This type of OLED is easy to manufacture but consumes more energy than the alternative system, for this reason they are ideal for small screens (1 "to 3") and alphanumeric.
Active Matrix OLED (AMOLED)
Complete anode and cathode layers are used, the matrix TFT (Thin Film Transistor) is on the anode. In this arrangement the TFTs are responsible for determining which pixels should be turned on or off.
One of its great advantages is that it consumes less energy than PMOLEDs and have higher rates of cooling, for this reason it is used in the manufacture of large screens (TVs, PC monitors, electronic signs, billboards).
Transparent OLED (TOLED)
In this type of devices all the layers are composed of transparent or semi-transparent materials, allowing the emission of bidirectional light through the cathode and the anode
Foldable or flexible OLED (PLED)
Thanks to the properties of OLED components in their manufacture can be used plastic substrates or flexible sheets and ultra-thin, which make them lighter, more durable.
Sony has been working in this area to develop screens that can be used in a number of applications such as televisions, cellular manufacturing, etc.
It is formed by stacking stations OLED layers to achieve the desired color light. This type of OLED allow us to replace conventional lighting systems such as fluorescent lamps may be generated as brighter lights in a more efficient and uniform manner, greatly reducing energy consumption.
OLED types of structures
Lower emission OLED
The light generated by the emitter layer travels inversely in the direction of the TFT circuitry, which partially blocks the light output. Its manufacture is relatively simple and consequently more economical, for this reason conventional OLED designs use the lower emission.
Higher emission OLED
Unlike the previous case in this structure the cathode is formed of a transparent material and the anode can be opaque and / or refractive allowing the light to travel frontally drastically extending the luminous area. The design of Sony uses this type of structure since it maximizes both the brightness of the image and the energy efficiency.
In addition to adopting superior emission, Sony developed its own Super Top Emission ™ OLED technology that incorporates a set of technologies such as micro cavities and color filters in the OLED structure.
Currently there are several products on the market that incorporate OLED screens, some of them: the TV (XEL-1) and in the professional monitoring area the PVN 740. In addition to the new Broadcast monitors of 25 and 17 inches (BVM-E250 and BVM-E170) manufactured by Sony.
There are many advantages of OLED technology, thanks to the characteristics of its components each pixel can be completely turned off allowing the reproduction of extremely deep blacks, in addition the contrast ratio of an OLED is excellent.
The switching time of the OLED is so fast that are no longer necessary frequencies Hz refresh 120 or 240 Hz to suppress blur in motion. For these and many other reasons is the future OLED technology display screens.
OLED technology will undoubtedly become the next generation of flat screens and is the key to the development of a wide variety of applications with ultra-thin and flexible displays, such as the development of smart clothing, lighting systems, cars with windshields that allow the visualization of the speed controls, GPS, telephone, etc., this and much more will be possible thanks to the great qualities of OLED technology.
Sony Broadcast & Professional Latin America (BPLA)