Light Emitting Diodes (LEDs) are very energy-efficient, but trap light very effectively. Although 70 per cent of energy from the LED is converted to light, a high refractive index at the LED-air interface means much of the light is reflected straight back inside, allowing just 20 per cent of light escapes.

Dr Faiz Rahman, a nanotechnology researcher at the University of Glasgow, believes LEDs have the potential to be as bright as ordinary bulbs, and has found a way to release the trapped light from the devices.

To extract more light from the LED bulb, Dr Rahman is puts millions of holes into its surface. These holes measure 200nm is diameter, are 400 times narrower than a human hair, and penetrate just 100nm into the LED’s surface.  Spaced 300nm apart, 160 holes fit across a hair’s width. Although a single LED chip may be around 0.3 x 0.3mm, that’s enough space for hundreds of holes.

Creating a lattice of these small holes over the surface of the LED semiconductor material changes the refractive index. It also reduces the internal reflections from the material’s surface which would otherwise trap emitted light inside.

Rahman explains: “In photonic-lattice patterned LED around 80 per cent of the generated light can be extracted. More, probably, would be possible by future design improvements.”

At first Rahman created the holes using an electron beam, but this proved costly and time-consuming. Now, using nanoprint lithography, Rahman is able to imprint the holes into LEDs at a far greater speed, and at a much reduced cost.

Rahman’s first LED devices are intended to replace cold cathode tubes in TVs, making the devices even thinner. He hopes to produce commercially available LED lightbulbs for the home within two to three years.

Read more at The Guardian