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Light emitting polymer is one of the so-called conjugated polymers. Electrical conductivity of these polymers is very different. In 1977, Alan J. Heeger and Alan G. MacDiarmid got noble prize for this invention. Their invention had a great impact on further innovations. The material was first used inside devices in 1989 and is being used in various circuit connections. Polymers have always been associated with revolutionary innovations in science and industry. Polymers have efficiently replaced insulators from a very long time. Polymers are chains of smaller molecular components called monomers.
Microelectronics and radio engineering successfully employed polymers due to their diversity and possibility of contraction from materials with various properties related to chemistry. Researchers are trying to develop compounds with non-linear characteristics under field effect. If successful, such researches may change the technology of key electronic components. The polymers enabled to produce from plastic and diverse electronic components such as transistors, sensors, high temperature wires and cables, panels, etc. light emitting diodes were the first electronic devices made of polymers. Structurally the design should ensure the most transparent electrodes. The electron transport layer and negative electrodes should provide for the maximum interference reflection and mirror reflection radiation.
We can now see that available researches and developments allowed producing their light emitting diodes on the commercial bases. Scientists work on the special type of conductive plastics. Conductive and light emitting plastics will change the nature of electricity altogether. For instance, the systems based on recently developed inductive polymers are entire in the market. Let us take a successful example of how polymers are used in laser engineering.
A laser based on organic materials is already available. It can easily be produced on commercial bases. Organic based lasers are much cheaper than semiconductors lasers. Moreover, a wide range of material covers a substantial spactrical range. We can say for sure that the nearest future will see a wide application of such lasers in optical devices and laser printers.
The possibility of printing electronic equipments like wallpapers might come into visibility in the time to come. Screens and displays will get benefit by these light emitting polymers. Lighting panels based on white light emitting diodes, electronic paper and many other things.
Light emitting polymers also known as LEPs is a rapidly emerging technology for next generation flat panel displays. LEPs promise thin, lightweight emissive displays that will consume fewer amounts of energy and power as well as fast switching times. On interesting application of these displays is electronic paper that can be rolled up like newspaper. Light emitting polymers are special plastic materials that concert electrical power into visible light. Polymer need to show floure sense and to conduct electricity to be a LEP. PPV stand for poly-pheneylene vinylene (PPV). The thin plastic film of polymer material sandwiched between two metallic electrodes. Electronic charges are injected into the polymer from the electrodes. The electrons and holes ‘capture each other’ through electrostatic interaction. Radioactive recombination of electron and brings out the light. An electric field is applied between two electrodes. The electrons are injected from cathode and holes from anode. The injected charges are then recombined and decay radioactively.
The construction of the light emitting polymer can be explained easily. The base is of a glass substrate. An indium tin oxide substrate layer also known as ITO has a layer above the glass. A conducting polymer layer eg PANI-CSA is above the layer of indium tin oxide substrate. Then there comes an emissive layer like a layer of MEH-PPV. Metal electrode is the top most layer of the light emitting polymer. There is a voltage source in the extreme right border.
The working of Light emitting polymers is a bit difficult. The basic LEP consists of a stack of this organic polymer layers sandwiched between a transport anode and a metallic cathode. The indium-tin-oxide (ITO) coated glass is coated with a polymer. Above it, there is a metal electrode having a layer of aluminum, Lithium, magnesium and Ag. These moving holes and electrons combine together to form hole-electron pairs known as “excitones”. When this energy drop occurs light comes out from the device. This phenomenon is called an electroluminescence. The greater the difference in energy between the hole and electron, the higher is the frequency to the emitted light.
There are many advantages of Light emitting polymers. They have relatively better display as compared to the other devices. LEPs are light in weight. There is absolutely no limitation in size. You can customize the size according to your personal preferences. LEPs have lower power consumption. They show a high quality imaging and a wide view angle. You can get any shade, color or any shape. It also shows a certain level of flexibility shape
Along with the advantages, Light emitting polymers also have some disadvantages. Some of the disadvantages shown by LEP are that they get damaged very easily by contamination of substrate surface. There is a constant fear of voltage drop. They are mechanically fragile. The real and true potential of Light emitting polymers has not been yet realized. They have a small lifetime.
There are various applications of Light emitting polymers. For example:
LEPs are promising, low cost solutions for today’s flat panel displays. Although Light emitting polymers have not yet commercialized yet still they do replace large, bulky and heavy CRT and LCD displays in the near future. However, LEPs have some gaps that need to be filled to get full advantages of this relatively new technology. For this, research is still in the process to improve the efficiency and lifetime of polymer displays.
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