From Popular Mechanics:
Solid-state lighting holds the promise of huge energy savings and long-lasting light sources. But before it comes to market, the products, like LED lights, have to get better, cheaper and easier to make. Here's how the U.S. Department of Energy is investing in a future illuminated by light-emitting diodes (LEDs) and organic light-emitting diodes (OLEDs).
At least that's the future envisioned by the Department of Energy (DOE). The agency announced $37 million in grants earlier this month in its sixth round of funding for solid-state lighting. The cash will go toward basic research, product development and manufacturing of light-emitting diodes (LEDs) and carbon-containing organic light-emitting diodes (OLEDs).
Together, these light sources offer huge advantages over conventional lighting. "[LEDs and OLEDs] can be more efficient than any light source available," says Jim Brodrick, lighting program manager for the DOE's office of Energy Efficiency and Renewable Energy (EERE). Compared to incandescent bulbs, solid-state lighting can be 10 times as energy-efficient and last hundreds of times longer. And LEDs can already easily triple the 10,000 hours or so of lifetime for compact fluorescent light bulbs, which are in today's lighting vanguard. Meanwhile, extending the life of OLEDs is a hot area of study that the DOE's grants will intensify.
LEDs and OLEDs are also durable, unlike incandescent lights with their fragile, superhot tungsten filament surrounded by glass bulbs, or fluorescent lighting's glass tubes that contain small amounts of energized mercury vapor. Most LEDs and OLEDs are tiny wafers—"they look like a squashed pea," says Brodrick—made of semiconducting metallic compounds, usually surrounded by hard plastics. "Solid-state lighting gets away from the motif of lighting as breakable," Brodrick says.
Beyond toughness and cost savings, the environment stands to gain from mercury-free solid-state lighting as well. Widespread deployment by 2030 could cut U.S. electricity use for lighting by a third, according to the DOE, and thus make a big dent in energy-related carbon emissions.
Given these major benefits, LEDs are already the light of choice for traffic signals and flashlights. (They have actually been used as red indicator lights on remote controls for decades.) But LEDs and OLEDs have so far failed to make serious inroads into residential and commercial lighting primarily because of cost and color.
Solid-state lighting available on the market today costs roughly three times as much as other lighting options, Brodrick says. This is largely due to the materials involved and the limited economies of scale compared to the long-established techniques for manufacturing incandescents and fluorescents by the hundreds of millions every year.
LEDs also have problems with light color—their whites appear too bluish and thereby render other colors poorly compared to traditional bulbs.
To address these issues, the 17 solid-state lighting grants issued by the DOE were awarded based on three categories. Core Technology grants totaling $4 million intend to fill in key technology gaps and expand the knowledge base. The DOE will sink $10.3 million into product development to refine products to be more functional, market-friendly and commercially viable. And for the first time, the DOE solid-state lighting grants will include a manufacturing category with $23.5 million to dole out.
Collectively, these grants seek to drive down costs while improving quality and developing new product-making techniques. The chosen companies will also chip in large sums of cash on their projects, bringing the whole solid-state research program to upwards of $66 million.
Here's a breakdown of how some of these 17 projects will bring about the next generation in lighting.
Core Technology ///
Grant Recipient Project Description DOE $ Total Project Value
Cambrios Sunnyvale, CA
Solution-Processable Transparent Conductive Hole Injection Electrode for Organic Light-Emitting Diode (OLED) SSL. This project seeks to develop a cost-effective replacement for indium tin oxide for use as an electrode in OLED lighting devices. Indium is both rare and very expensive.
University of Rochester Rochester, NY Development and Utilization of Host Materials for White Phosphorescent OLEDs. This project seeks to produce white OLEDs with > 100 lm/W efficiency after light extraction enhancement and > 10,000 hour operating time, by making a new class of emissive materials. $1,239,071 $1,376,746 WhiteOptics, LLC Newark, DE Low-Cost, Highly Lambertian Reflector Composite for Improved LED Fixture Efficiency and Lifetime. This project seeks to demonstrate a highly reflective, highly diffuse, low-cost composite material that is able to withstand at least 50,000 hours of luminaire operation. $1,556,316 $1,967,373
Cheaper ElectrodesThe Cambrios company, out of Sunnyvale, Calif., is hoping to develop a new electrode for energizing OLEDs that's cheaper and better than the indium tin oxide used now. The trick will be finding "a new substance that's transparent and also conducts electricity," Brodrick says.
Evenly Dispersed ElectronsAnother technical challenge will be spreading electrons that are introduced at the corner of an OLED square evenly across the whole sheet of material. The University of Rochester will tackle this problem with an emphasis on improving light extraction from OLEDs with new materials. Just like regular LEDs, these thin lighting sources absorb some of the photons (particles of light) they produce, so different coatings and structural add-ons—such as "photonic lattices" which are full of holes that channel light out—continue to be investigated.
Higher OutputTo boost output from the rest of a light-emitting fixture, the Delaware-based company WhiteOptics makes a special plastic that reflects 97 percent of light in a diffuse, eye-friendly manner. This could be significant for LEDs because they are typically point-sources of light, cranking out a lot of lumens from a bright, hot area that is mere millimeters square, says Eric Teather, founder and president of WhiteOptics. Lighting designers often place multiple LEDs in clusters to produce the equivalent of other lighting sources, but this can give the light a piercing, pixelated appearance. "People are not used to seeing dots; they want to see uniform, well-distributed light," Teather says. Lenses are sometimes placed over the top of the LEDs to direct and disperse the light, but these can cut into output, Teather says.
The DOE grant to WhiteOptics will go toward improving the reflectivity of the company's proprietary material, which can further reduce the number of individual LED chips needed in a fixture. Teather says he has concept materials that reflect 99 percent of incident light. WhiteOptics has previously demonstrated that its reflective plastics can improve lighting efficiency by 15 to 20 percent. These efficiency gains cut almost dollar-for-dollar into overall costs, Teather says, because the most expensive part of an LED fixture is the LEDs themselves, with the reflective plastic coating just a fraction of the overall price. In addition, the reflective plastic will be geared for long life—50,000 hours, or pushing six years—and will be low-cost. Teather expects to deliver on this technology in about three years....MUCH MORE