Purdue LED Breakthrough

by Michael Graham Richard

Five Times As Efficient, Way Cheaper

Better, Cheaper LEDs
The incandescent lightbulb that wastes 90% of the electricity as heat is dying, we all know that. But a new breakthrough in solid state lighting might also kill compact fluorescent lightbulbs (CFLs) faster than some expected. Scientists at Purdue University have figured out how to manufacture LED solid-state lights on regular metal-coated silicon wafers (more details below). What this means is: much lower costs.

10% Reduction in Total Electricity Use
And since about 1/3 of U.S. electricity is used to produce light, this is major. "If you replaced existing lighting with solid-state lighting, following some reasonable estimates for the penetration of that technology based on economics and other factors, it could reduce the amount of energy we consume for lighting by about one-third. That represents a 10 percent reduction of electricity consumption and a comparable reduction of related carbon emissions," said Timothy D. Sands, professor of Materials Engineering and Electrical and Computer Engineering states at Purdue.

Old LEDs vs. New LEDs
What makes traditional LEDs so expensive is that the light-emitting layer of an LED light is a gallium nitride crystal and it needs to be treated in various ways with expensive materials.

Dailytech:

In sapphire based LEDs, used for green or blue lighting, mirror-like reflectors are need to reflect and resend emitted light, increasing the efficiency. Typically, this layer is extremely expensive to produce, part of the reason the current generation of LED lighting costs so much, costing at least 20 times more than conventional incandescent and fluorescent bulbs. Also, the LEDs are built on sapphire crystals, which provide the color, but are extremely expensive.
But the new LEDs can be made using standard silicon wafers and already existing, less expensive, processes. This would make them competitive with incandescent and CFLs.

The new techniques yield a crystalline structure aligned to the crystalline silicon. This means that the LEDs are less prone to defects and will perform more efficiently [...] silicon dissipates heat more effectively than sapphires. This will reduce damage during operation and lead to longer lifetimes and more reliability..
We might soon have to get used to changing lightbulbs every other decade.

LEDs that are currently available convert electricity to light with an efficiency of 47 to 64%. It is predicted that LED produced with Purdue's process would have an efficiency in the high-end of that range, compared to about 10% for incandescent.