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Quantum Leap for LED Lighting: New technology makes great strides in color rendering

By Chuck Ross | Apr 14, 2023
EC2304_Quantum-Feat_spread_QLED
There’s no question that the move to LED lighting has substantially decreased the amount of energy we use to illuminate our buildings over the last decade. But manufacturers seeking to drive down energy use further have historically run into a challenge: light quality—how well lighting renders colors—can diminish as fixtures and lamps become more efficient.

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There’s no question that the move to LED lighting has substantially decreased the amount of energy we use to illuminate our buildings over the last decade. But manufacturers seeking to drive down energy use further have historically run into a challenge: light quality—how well lighting renders colors—can diminish as fixtures and lamps become more efficient. A rapidly evolving technology could help developers address this conundrum by using new phosphors that enable LEDs to emit specific colors more accurately and target only colors within the visible spectrum.

These quantum dot phosphors have been used in LED displays for several years, but using them in lighting applications has been difficult until recently. Now, manufacturers are beginning to introduce LEDs that enable more efficient and higher-quality lighting. Quantum dot products are also impacting the burgeoning field of human-centric illumination by helping to reinforce our natural activity levels throughout the course of the day.

Hitting limits

In just a few short years, LED products have moved lighting from one of a building’s highest energy loads to one of its lowest. In late 2022, the U.S. Energy Information Administration (EIA) released the results of its 2018 Commercial Buildings Energy Consumption Survey, which showed that overall commercial building energy intensity had decreased 12% between 2012 and 2018, with electricity intensity declining 14% and natural gas intensity down 11%. 

During the same period, LED lighting went from being present in 9% of surveyed buildings in 2012 to 44% in 2018. While the drop in energy intensity might not be entirely due to LEDs, their higher lighting efficiency and cooler operations surely played a role in this shift.

To further boost LED efficiency, manufacturers are having to consider new approaches to maintaining light quality, which is measured along a scale called the color-rendering index (CRI). This metric ranks light sources according to how well they reveal objects’ colors compared to a natural light source like the sun, with a CRI of 100 representing light that’s indistinguishable from natural daylight. While some manufacturers are advertising lamps with CRIs as high as 99, most commercial products now fall into the 80–90 range.

To achieve higher CRIs, manufacturers must focus on the red end of the visible spectrum, which is the most difficult for LEDs to accurately render. They’ve had to incorporate LEDs with wide-spectrum red phosphors to improve this performance. However, in addition to producing reds that improve color rendering, these phosphors also produce reds that are outside what the human eye can see—so that energy is essentially wasted.

Quantum dots address this shortcoming by enabling very precise, narrow-band color rendering. The dots themselves are incredibly small, with diameters ranging from 1–10 nanometers (or 10–50 atoms). That’s approximately 10,000 times smaller than the diameter of a single human hair. The color emitted by these semiconductor nanocrystals is based on size, with the smallest-diameter dots producing bluer light and the largest dots emitting redder light. Manufacturers are focused on the larger, red quantum dots because they see them as a way to maximize efficiency and CRI by narrowing the bandwidth of red those LEDs produce. That way, energy isn’t lost creating red wavelengths the human eye can’t see.

“Red is the low-hanging fruit.Quantum dots take those photons into the specific red region you’re targeting, instead of losing them to the infrared.”
—Peter Palomaki, Palomaki Consulting

“Red is the low-hanging fruit,” said Peter Palomaki, owner and chief scientist at Palomaki Consulting, Billerica, Mass., which specializes in quantum dot development for display and lighting applications. “Historically, for high-CRI products, manufacturers would use a red phosphor that was broad, so you’d also get a lot of light into the infrared spectrum. Quantum dots take those photons into the specific red region you’re targeting, instead of losing them to the infrared.”

Quantum dot displays and TVs, such as Samsung’s QLED models, started showing up on the market in 2013, but lighting has been a more challenging application, Palomaki said. In displays, the dots are dispersed in a polymer film that’s separated from the illuminating LEDs. In lighting, though, they’re applied directly onto the LED, where heat and light intensity can take a toll. “It’s taken longer to become commercial because of the physical requirements to survive on an LED for 50,000 hours—historically, quantum dots couldn’t withstand those conditions.”

Circadian lighting applications

The Austrian manufacturer ams Osram introduced the first lighting LED with quantum dots in 2019 following its acquisition of Pacific Light Technology (PLT), a California-based pioneer in the technology. PLT developed a methodology for applying the dots to LED chips so they can be a drop-in replacement for traditional phosphors during the fabrication process. These ams Osram LEDs are starting to show up in new lighting products designed with quantum dots in mind.

These include offerings from startup Nano-Lit, Vancouver, British Columbia, which is incorporating ams Osram’s quantum dot LEDs into fixtures that support our circadian rhythms (the ways our bodies respond to shifting tones of natural daylight and darkness throughout the day). When we’re in tune with those rhythms, we’re more likely to enjoy healthy sleep patterns and wake feeling rested in the morning.

 ams Osram’s Quantum Dot is versatile and offers a multitude of design solutions for interior lighting applications such as office, retail, hospitality, residential and hospital lighting.

osram / jeedlove / kanyanat

“We’re the first company in the world to manufacture quantum dot lighting successfully,” said Sarah Morgan, Nano-Lit founder and CEO, who says her company’s proprietary technology developed through efforts toward an even more ambitious goal is still in the works. “Our long-term mission is programmable paint.”

Circadian lighting is a rapidly growing field of study—you might already be setting your smartphone screen to follow a backlighting schedule that has it dim down as the clock moves toward bedtime. LEDs’ controllability provides strong support for the approach. Manufacturers can incorporate chips that each illuminate at a different color temperature, from the warm, yellow-y 1,800 degrees Kelvin (K) of candlelight up to the cooler 6,000K or higher of natural daylight at midday. Control algorithms shift power to these chips to create mixes of color temperatures and lighting intensities to help guide our bodies to healthier sleeping, waking and working schedules.

Real-world applications

“You’re driving different chips differently” so more or less power goes to specific chips, Palomaki said, explaining how this kind of “tunable” white lighting works. “You’re just creating a different ratio of power between the chips.”

Nano-Lit’s Artemis is an indoor lamp designed to mimic the natural light-dark cycle and sync circadian rhythms.
nano-lit

Nano-Lit initially targeted commercial settings, such as offices, senior living facilities and schools for its tunable systems. These spaces are where occupants could especially benefit from lighting that supports productivity and health. In nursing homes, for example, brighter, bluer daytime lighting can help residents stay awake and engaged. Shifting that light to warmer tones as afternoon starts moving to evening is thought to help minimize the emotional stress—often called “sundowning”—that dementia patients can suffer in early evening. It also is thought to help set the stage for a better night’s rest by triggering the sleep hormone melatonin, which we have less of as we age.

“Senior care is the fastest growing market for us,” Morgan said. “The level of knowledge within their employees is pretty impressive. They understand the impact of light on behavior throughout the day.”

Nano-Lit worked with several circadian lighting experts to develop “prescriptions” to address the 24-hour lighting needs for specific applications. The company’s quantum dot technology is especially helpful in this regard because of its improved wavelength control, especially in the red region of the visual spectrum, and its ability to minimize blue light more than standard LED phosphors. The International Well Building Institute, developer and administrator of the WELL Certification program for healthier buildings, recently installed Nano-Lit-powered troffers and linear fixtures in its headquarters. The organization’s WELL V.2 standard incorporates circadian principles into its updated lighting section, and Nano-Lit’s technology was used to set the standard.

Now, Nano-Lit has released a table lamp that features quantum dot LEDs to create similar circadian support. The Artemis fixture debuted after a Kickstarter campaign and features a slimlined design and its own programmed lighting prescription to promote healthy sleep-wake cycles.

Moving forward, Palomaki sees demand for quantum dot lighting growing slowly over the next three to five years, due to the premium the technology adds to standard LED pricing. 

“I think it will probably still be in niche markets—in the large-volume consumer market, it almost always comes down to price,” he said, noting that, even as a lighting expert, he is as cost-conscious as most other shoppers. “I buy LED products and look at the price first, and then at the metrics.”

Morgan, though, is focusing her business on those markets where her products’ circadian functionality has particular appeal. And she’s looking at building ongoing relationships with those customers in ways that would allow further refinement of installed fixtures as research on lighting’s health affects advances.

Lighting as a service

“We’re doubling and tripling down on lighting as a service (LaaS),” Morgan said, describing an approach in which lighting purchases are treated more like a monthly subscription instead of an upfront capital expense. The company’s software enables Nano-Lit to download new prescriptions to customer-­sited equipment. During the pandemic, Morgan said the company used that capability in its work with research labs studying circadian rhythms trialing Nano-Lit equipment. They needed the ability to make small adjustments to Nano-Lit equipment in real time as they worked to refine their understanding of the specific color temperatures, intensities and timing needed to maximize lighting’s potential health benefits.

“That told us that not even the experts are fully aligned on what is the right schedule for, say, healing—we need to get more and more precise,” she said, explaining how an LaaS model could allow customers’ systems to be regularly updated as research progresses. “We deliver the hardware, which is highly flexible, and we can update it remotely or on the spot.”

feature image: shutterstock / Titima Ongkantong / Milky_way.nn

About The Author

ROSS has covered building and energy technologies and electric-utility business issues for more than 25 years. Contact him at [email protected].

 

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