Cost has been a major barrier in keeping people from buying energy-efficient LED lightbulbs.

Now one of the world's largest LED makers, Osram Opto Semiconductors, says it has perfected a technique that could significantly cut the production cost of LEDs.

White LEDs are typically made by coating blue gallium-nitride LEDs with yellow phosphors. Manufacturers normally grow the gallium-nitride in thin layers on top of costly sapphire substrates. Osram is making the devices on silicon substrates instead. Silicon substrates cost a third as much as sapphire and could get even cheaper, since they're made in larger pieces.

The company says its silicon-based white LEDs produce 127 lumens for each watt of power, with a power efficiency of 58 percent, comparable to state-of-the-art commercial LEDs grown on sapphire. Peter Stauss, a project manager at Osram, says researchers are now testing and optimizing the devices, and expect to start selling them in the next two to three years.