Faiz Rahman, a nanoelectronics researcher at the University of Glasgow, predicts that LED light bulbs for the home will start appearing on store shelves in the next 2-3 years to compete with incandescent and fluorescent bulbs.
If so, the LED bulbs would provide a much greater efficiency (up to 70%) compared with incandescent (5%) and fluorescent (25%) bulbs.
Rahman is working with researchers from a number of different European universities to make LED light bulbs ready for consumers. The main challenge is in preventing the LED's light from getting reflected back inside the device, and instead getting the light to come out and shine. Although 70% of an LED's energy is converted to light rather than heat, only about 20% of that light escapes.
To improve this extraction level, the researchers' solution is to make hundreds of small holes in the LEDs. At just 200 nm in diameter, 160 of these holes placed 300 nm apart could fit across the width of a human hair. But when each LED is punctured with thousands of these holes, its refractive index can be changed to allow more light to escape the bulb. With this strategy, Rahman has created LEDs where 80% of the generated light can escape, and predicts that this could be improved further.
Currently, the greatest roadblock to manufacturing these LEDs is due to their expensive, time-consuming fabrication. One possible solution is nanoimprint lithography, where an intricately patterned stamp could be used to imprint holes in several LEDs at a time.
Besides efficient light bulbs, Rahman adds that the LEDs could also be used as backlights in LCD TVs. By replacing cold cathode tubes, they could make the TVs even thinner.
