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Introduction to Lighting Technology: Led and Oled

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Introduction to Lighting Technology: Led and Oled INTRODUCTION TO LIGHTING TECHNOLOGY: LED AND OLED М.І. Карпенко студент , Факультет елетроенерготехніки та автоматики Національний технічний університет України “ КПІ ” The light-emitting diode, or LED, is the basis for future lighting technology. This two-lead semiconductor produces light when being activated, and it is a very important device, because it finds wide application in the everyday life. Numerous indicators in our household appliances, for example, in remote controls, games- consoles, lamps, computers, etc. help us do work, communicate, and entertain ourselves. Many modern cars are equipped with LED indicators and brake lights. Also, we should not forget about traffic lights, signs, street lighting and so on. These diodes reveal the interconnection between electronics and photonics. In fact, the LED is a vital link to understanding these fields of science. The main reason why LED are so domination in these branches is that they are commonly used in broadband communication. Nowadays most people think that LED-technology has been recently discovered by US scientists. However, the light-emitting diode was actually invented by Henry Round, and Oleg Losev, one of the Russian scientists that are now forgotten, almost 100 years ago. 30 There are two main types of the light-emitting diodes – LEDs and OLEDs. There are also EL lamps (Electroluminescent Lamps), but there is a difference in the construction. The LED has special reflectors and other parts to make the light brighter and to focus it on one point. The OLED is different, because it’s a compound. The abbreviation OLED stands for “organic LED” and its layer consists of a mix of substances, just like in EL lamps, but it uses carbon molecules. A lot of people do not know that the LED is quite an old technology and as a matter of fact it was created over 50 year ago. We should thank such people as Robert Hall, Nick Holonyak from Syracuse, Marshall Nathan from IBM and Robert Rediker from MIT for being able now to apply it in practice. This technology has some advantages and disadvantages. The pros: 1. It requires only 30-60 volts for proper work. That makes the LED one of the most efficient sources of light for areas with small space. 2. Extended life time duration in contrast to glass bulb lamps. 3. It can help to reduce stray light pollution of streetlights. The cons: 1. Sensitive semiconductor may be damaged by the heat. As a result, the complete lighting system may go out because of problems with one LED. That makes us provide heat sinks to protect the lamps. In its turn, this reduces efficiency of using LEDs, and costs more money. 2. The LEDs include some rare components. Their price can be monopolized by some countries. 3. It sometimes reduces lumen output. 4. The LEDs may get cracked because of the specific strict construction with thin cooper connections. 5. There is a great gap between summer and winter temperatures, so it may cause whole sections of streetlights o go out, but this problem will be solved in a few years because a lot of work has already done in this research area. 31 The organic LED’s layer is made of molecules, including carbon, providing electroluminescent effect. Nowadays, we use them for small and large displays, and lamps. The OLED can make a revolution in our world, and may become an important part of subjects in which we have never used the lighting technology before. If we compare an organic LED to its previous generation, we will find out that the first one is more efficient on the market of displays, it produces more light, it responses quicker and it is thinner. Unfortunately, the price of lighting devices of a new generation is higher than that of LEDs, but this problem is common for all new technologies that are at the stage of development. Another goal for today’s scientists is to make OLEDs’ time life duration longer, because at present organic materials may crack just in a few years. The most perspective way for OLEDs’ development is in display production. Now we all have some kinds of monitors in our houses and workplaces, for example, computer, television and phone screens. The OLED is the best device to replace LCD in these products. The OLED display is made of a few different layers along with transistor that sends the signal to each pixel to turn on or off. This display may be thinner and more efficient than LCD. It also has better contrast and displaying blacks. With flexible shell, this monitor will make a revolution in appearance of our gadgets. We will be able to roll up it like a newspaper. Despite the fact that OLED monitors are not so bright as LCD or EL, they work better in less lit areas and have bigger watching angle. In the future OLEDs will become the basis of full colour, flexible and thin displays. REFERENCES 1. Zheludev N. The life and times of the LED – a 100-year history // Nature photonics. – Vol. 1. – April ,2007. – P. 189-192. 2. LEDs and OLEDs. Edison Tech Center [Електронний ресурс ]. – Режим доступу : http://www.edisontechcenter.org/LED.html#work. – Назва з екрану . 32 3. Monroe, D. Synopsis: A Single-Molecule Light-Emitting Diode [Електронний ресурс ]. – Режим доступу : http://physics.aps.org/synopsis- for/10.1103/PhysRevLett.112.047403. – Назва з екрану . 4. OLED with Carbon Nanotube as Hole Injection Layer [Електронний ресурс ]. – Режим доступу : http://www.ee.surrey.ac.uk/NEC/OLED.html. – Назва з екрану . 33 .
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