Recent progress in technology starts to make solid state lighting practical

Recent progress in technology starts to make solid state lighting practical

Paula Doe, SEMI Project Manager

Surprisingly big progress over the last couple of years in low energy semiconductor-based lighting is enabling some real commercial applications, potentially generating a $1.4B market within five years. Producers now look to semiconductor materials and equipment suppliers for the technologies to enable low cost volume manufacture.

Semiconductor-based lighting could cut the energy used by lighting in half, says the US Department of Energy. And since lighting accounts for about a fifth of all electricity used in the US, that could add up to some $98 billion in energy savings by 2020. DOE figures just replacing the country’s 60W bulbs with 10W LEDs would save enough electricity to power all of Las Vegas for a year – twice. Indeed the government is so keen on the idea it’s offering up to $20 million in prize money to developers of viable commercial fixtures meeting its standards.

That dream is now a lot closer than people thought only a couple of years ago, as solid state lighting technology made surprisingly big strides over the last year or so in getting more useable light out of the devices. That–and growing consumer and corporate interest in reducing carbon emissions—are starting to make the technology viable in an increasing number of market niches. The LED lighting market jumped 60% in 2007 to $330 million, according to Strategies Unlimited, which projects a $1.4 billion market by 2012.

“Quite recently LEDs have been coming into the general illumination market, where they’re replacing incandescents and halogen in retail displays, commercial premises, and outdoor lighting, though the cost is still generally too high for residential,” says Robert Steele, director, optoelectronics, for Strategies Unlimited. “Light per LED package has doubled in the past two years, while cost has gone down 10% or so, so we’re getting more than twice the lumens per dollar….It’s not a stretch to see 10x more light output within five years, for a 10x decrease in cost.” Government incentives will likely spur demand, as utilities in California plan a $2B dollar incentive program likely to start within a year, and as mandated performance standards effectively phase out incandescent bulbs within 5-10 years.

One supplier claiming real progress is Cree LED Lighting Solutions (Morrisville, NC), with its recessed downlight fixture that it says puts out the equivalent of a 65W incandescent bulb while using only 12W. CTO Gerry Negley says hotels, restaurants, hospitals and offices are opting for them for the high quality of the light, and the reduction in electricity and maintenance costs. Payback period for one Friendly’s restaurant in Waverley, MA, was within one year, reports Negley.

Bucking the conventional approach of choosing the blue LED and the yellow phosphor top coating to get the best white light, the company instead chooses the most efficient blue LED and the most efficient yellow phosphor coating, though that makes yellow –not white-- light, and then adds an efficient red LED to make white. Negley notes the company has demonstrated efficacy as high as 113 lm/W. “It was very expensive,” he says. “But in a couple of years it will be common.”

Caption:

Makers of solid state lighting have improved light output markedly over the last two years, particularly for cool white light.

Source: Strategies Unlimited

Luminus Devices (Billerica, MA) is also now pushing into solid state lighting market, says founder and CTO Alexei Erchak. His company has been mass producing its high brightness LEDs for projection televisions and projectors since 2006, and will start to supply them for LCD backlights later this year. It now aims at other applications that require lots of light from a single source. A single, large, higher power chip simplifies the optical design and may prove less costly than assembling the typical array of small LEDs. The company recently raised an additional $72 million in venture capital to expand into new general lighting markets.

While most light escapes from a typical small-chip LED from the sides and edges, Luminus tops its devices with a photonic lattice pattern to extract more light from the chip’s surface, so it can make a larger device, allowing it to run at higher power and with greater total light output. Erchak notes, however, that an equally important aspect of Luminus’ PhlatLight technology is the packaging, where Luminus uses new materials and processes to manage the heat effectively enough to maintain reliability despite putting up to 100W into a single device.

 

Source: Luminus Devices.

Caption: Photonic lattice gets more light out from the surface, allowing larger device.

Lighting makers count on semiconductor supply chain to bring down costs

Despite major recent strides, there’s still plenty of opportunity to bring down LED costs. Yields remain a problem, notes Strategies Unlimited’s Steele, as the chips vary by wavelength, light output, and voltage, and then they’re topped with a squirt of phosphor in epoxy that adds even more variability, leaving a lot of chips that don’t meet standards on one of the three measures.

“We haven’t found the right chip or package yet,” says Cree’s Negley. The LED community is just starting to understand what the lighting community needs.” He argues the key issues now are developing better drivers to convert down to the low 3V level needed for the LEDs, and better encapsulants that don’t optically degrade in light and heat. “With most materials, we know how they behave with temperature, but we don’t know how they behave with light,” he says, noting that the LED operating conditions are far more severe than those for photovoltaics. “It’s a question of finding the right polymer engineers and making them understand the problem.”

“We’re finding lots of companies to look at,” says Robert Walker, principal, Sierra Ventures (Menlo Park, CA). “We see the best opportunities around the infrastructure, for example the thermal and electrical parts of the system, like the current drivers.” He notes that driver burnout is often where LED systems fail, as both the heat of the real operating environments and the extreme lifetimes expected require new approaches from suppliers. “People aren’t used to making stuff to last 50,000 hours,” he notes.