A new light on energy efficiency
A quarter of the total energy used in Europe is for lighting purposes. Current research efforts are focusing on new technology with the potential to halve European lighting costs.
Dresden's City Museum is saving energy by controlling their more than a thousand fluorescent tubes and halogen spots through a computer network. This set-up allows the intensity of each light to be individually changed, depending on the natural light conditions, and allows for the programming of various lighting modes. The museum is just one example of the "smart lighting" systems that are becoming common practise around the world. However a much larger potential to improve energy efficiency exists in updating the light sources themselves.
A European project is aiming to develop technology based on organic light-emitting diodes (OLEDs) to create a new, revolutionary kind of light source. The standard light bulb is very cheap to manufacture, but most of the energy it uses is converted into heat rather than light, which is why light bulbs can become incredibly hot. Organic LEDs are about twice as efficient as compact fluorescent lighting and 8 times more efficient than traditional incandescent lighting. Many researchers and industrial developers are becoming increasingly interested in organic LEDs. Although they use much less power, they can produce light as bright as any standard light bulb.
Inorganic LEDs have been used for many years as spot lighting. But organic LEDs do not just produce tiny spots of light, they can produce large glowing surfaces. The origins of this technology dates back to the 1950s with the discovery of electroluminescence, whereby some materials emit light when an electric current passes through them. The current OLED technology is still at an experimental phase. Only very small OLEDs are being produced in small numbers. Even the manufacturing of these small OLEDs is too expensive for any large-scale production.
The chemical components used in the production of OLEDs are cheap and abundant, but the manufacturing processes are rather complicated. Since the materials are organic they cannot come in contact with air, otherwise they oxidise. Glass substrates are kept in a vacuum chamber, while they are covered with organic material, adjusting the amounts for different colours. The result is a thin film (about a thousand times thinner than a human hair) of organic semiconductors between two electrodes in an airtight enclosure. The organic film then illuminates when a current flows through it.
The existing prototypes show how the OLEDs reach their full intensity instantly after they are turned on and how the brightness can be easily adjusted. Another valuable characteristic of the OLEDs is that they can become transparent when they are not emitting light. OLEDs could therefore be integrated into windows, furniture, walls, ceilings, mirrors or any other smooth surfaces. A further possibility for the future will be flexible OLED lamps that can be wrapped around other objects. This could be done by using transparent plastics instead of glass substrates.
At the moment a lot of researching effort is going into making the technology feasible for mass production. A major problem is that even a simple dust particle can render an OLED useless before its production is completed, which makes the production of larger OLED panels incredibly complicated. Another problem is that the OLEDs lose brightness over longer periods of time.
Six European countries are taking part in the project, which is being coordinated from Aachen in Germany. The aim for its completion in mid-2011 is an OLED that is up to one square metre large, has twice the energy efficiency of a fluorescent tube, has a long live and is cheap to produce. To achieve this goal researchers from various fields including chemistry, physics and engineering are working together.
The possibility of having flexible lamps covering large areas leads to a wide range of applications for these highly efficient OLEDs with exceptional colour rendering. With the arrival of organic LEDs the light bulbs of today will seem like the oil lamps or candles of the past.