Lighting residential and commercial buildings accounts for about 1/4 of all electricity used in the U.S. according to the Department of Energy, and since most of that light is produced very inefficiently (incandescent and halogen light bulbs could be called "heat bulbs"), there is potential for huge savings.
Compact fluorescents (CFLs) are a step in the right direction, even though they have downsides such as mercury (even more mercury comes from coal plants), but light emitting diodes (LEDs) remain the most promising next step: more efficient, longer lasting.
Researchers at Bilkent University in Ankara, Turkey, have made a discovery that brings LEDs closer to widespread adoption. They discovered that by coating blue LEDs with a layer of nanocrystals specially engineered to turn the blue light into warm white, they could produce light at efficiency of over 300 lumens of visible light per watt. "Typical white LEDs are less well matched to human eyes and provide only about 30 to 60 lumens of visible light per watt," so these would be 5 to 10x better! That's also better than CFLs which are closer to 80 lumens/watt.
The crystals absorb some of the LED's blue output and emit their own red and green light. That combines with the remaining blue light to produce a soft white glow.
Existing commercial white LEDs are also based on blue LEDs. But they use a phosphor coating that converts some blue light into a broad spectrum of yellow light. When mixed with remaining blue light the result is a harsh blue-hued white.
There's still a way to go before crossing the finishing line, bu we can hope that figuring out how to make this nanocrystal coating inexpensively won't take too long now that we know it's possible.