By IAN AUSTEN

Solid-state lighting technology has long performed many electrical tasks, but Thomas Edison’s bulb still largely rules. Solid-state, which uses light-emitting diodes, is usually relegated to niches like automobile taillights, Christmas decorations and the humble flashlight.
That may be changing. Attracted by the low power demands of solid-state lights, which use semiconductor materials, the Department of Energy is financing projects to overcome technical and marketing problems that have prevented the technology from successfully challenging more conventional incandescent and fluorescent lighting. “It will involve multiple paths of attack, said Alexander Karsner, the assistant secretary in the department’s office of energy efficiency and renewable energy.
But the technology issues may not be the sort that immediately come to mind, like compatibility with light fixtures. The industry’s experience in persuading consumers to swap traditional bulbs for more efficient compact fluorescents has provided lessons for advocates of solid-state lighting. Compared with traditional bulbs, some compact fluorescents emitted a cold, bluish light that was not very cozy.
Solid-state lights, however, should allow manufacturers to fine-tune the tint of their output to better suit consumers’ tastes.
“Because they’re fundamentally silicon, computer-driven devices, the capability to manipulate them and do things with them is almost unlimited, Mr. Karsner said.
There are two technologies for solidstate lighting: light-emitting diodes, or L.E.D.’s, and organic light-emitting diodes, commonly called OLEDs.
L.E.D.’s are the most familiar. While tiny L.E.D.’s used as indicator lights are inexpensive and well developed, highpowered L.E.D.’s suitable for lighting face two major obstacles. The brightest models can be very expensive, and can produce even more heat than conventional bulbs.
Increased production is helping with costs, and L.E.D.’s have given off more light and less heat with each new generation. But most conventional fluorescent and incandescent bulbs flood rooms with a broad, diffuse light. L.E.D.’s, by contrast, are what the industry calls point sources. They provide only directed light.
As a result, Mark McClear, the director for business development at Cree, a major L.E.D. maker, expects that the lights will first find a place as a substitute for halogen bulbs, which have a similar directed quality.
OLEDs do not resemble computer chips, as do L.E.D.’s. They are generally much larger and often made on flexible plastic bases. The organic part of an OLED comes from the carbon-based compounds that are layered between two transparent electrodes. When a current is applied, the organic material glows.
Janice K. Mahon, vice president for technology commercialization at Universal Display, said that there were still technical hurdles to overcome before OLEDs replace fluorescent panels or appear as more imaginative lighting fixtures. But, she added, “the second challenge is getting the entire industry to adapt to this new technology.