LEDs have been used in electronics since the 1970s, but only recently have they entered—and transformed—the lighting and architectural design markets. Now LEDs are firmly established as energy-efficient replacements for incandescent and fluorescent lamps, as can be seen by the dearth of the latter products at industry trade shows.
Advances in solid-state lighting (SSL) technologies have made individual diodes smaller, brighter, more cost effective, and more versatile. The U.S. Department of Energy projects that switching indoor and outdoor products from conventional light sources to LEDs will result in a 75% reduction in energy use—a savings of nearly $630 billion—from 2015 to 2035.
In the past, advancements in SSL by scientists and manufacturers often arose through trial and error, but research in this product category has become more methodical and purposeful. This article outlines recent achievements in the evolution of SSL technology.
Manufacturing Progress
LED fixtures have come a long way, from improvements in performance, articulation in size, shape, form, and physical interfaces. The efficacy of LEDs—how efficiently the diodes themselves perform, measured in lumens per watt—has significantly increased while their cost has decreased, but room for improvement in the efficiency of the overall fixture still exists.
According to the 2017 U.S. Department of Energy report “LED Efficacy: What America Stands to Gain,” the highest performing LED devices (at the time of the report’s publication) could emit 160 to 170 lumens per watt. The DOE projected that the use of phosphor-converted (pc-LED) architectures could increase efficacy to 255 lumens per watt.
Fixtures are also becoming more compact. Chip-scale package (CSP) LEDs eliminate the need for a package, or the casing that encapsulates an LED chip and phosphor. Furthermore, replacing ceramics—widely used in packages for their thermal management properties—with enhanced polymer materials can make the price point more competitive without detriment to the quality and performance of LEDs. Because manufacturers are able to use fewer LEDs to create the same effect, they can achieve more compact designs, increase visual comfort, and lower fixtures costs.
Quantum dots has the potential to produce more effective and affordable systems. “White illumination in LED fixtures is primarily based on phosphor conversion,” says Marc Dyble, a Detroit-based product marketing manager for German lighting manufacturer Osram, “and despite advancements over the last decade, the efficacy gap has remained stable. Developments in the technology behind quantum dots—tiny semiconductor particles that can emit light and can be as small as 10 atoms in diameter (about 10,000 times smaller than the diameter of a single hair)—will significantly reduce the production cost of LED lighting systems.”
Smart LEDs, which combine the LED driver and control interface into a single package, can do more than emit or detect light. So-called intelligent red, green, and blue controls in the form of Smart RGBi can further eliminate the need for additional components. These LED fixtures can be adjusted in multiple ways, from the beam angle to the direction and illumination of an LED source, without the need for complex optics.
Advancements in manufacturing translate into better product applications and ultimately improve the user experience. Tasks such as navigating through a hospital to find a patient room, Dyble says, “can be made easier with customizable messaging projected onto wall or floor surfaces from luminaires simply based on your location. Further developments in the color-over-angle performance of LED sources reduce yellow and blue color striations, resulting in a uniform color appearance from the lighting fixtures illuminating the walls of the hospital hallway.”
Humans at the Forefront
Beyond efficacy and efficiency, the industry is embracing a more holistic approach to lighting. “LED suppliers are seeing the benefit to manufacturers of joining together multiple systems like color tuning, dim to warm, and circadian rhythm,” says Michael Giardina, a Los Angeles–based product manager at Acclaim Lighting.
These innovations have helped spark interest in human-centric lighting (HCL), commonly called circadian lighting, which aims to support human well-being and productivity through dynamic lighting sources. Advancements in LED technology have fostered the creation of tunable white light systems, which mimic daylight by adjusting correlated color temperature and brightness levels throughout the day. “We have moved past the point of static lighting—such as the fluorescent lights in an office space or incandescent lights in a home—to tailoring the light spectra to the time of day, essentially mimicking daylight indoors,” Dyble says. “Improvements to the quality of light—or color fidelity—of LED sources have also been a major focus using novel phosphors, all the while maintaining high efficacy.”
“The research and technology behind tunable white systems are now reasonably mature, though more advanced control systems and higher output options are coming to market all the time,” Giardina says. “The value in tunable white systems now lies in the education and adoption of the technology by a broader swath of the general public.”
Quantum dot technology can also enhance human-centric lighting because of their ability to be precisely controlled and programmed. The output is rich, saturated colors that mimic real sunlight. The resulting dynamic lighting might even improve circadian rhythm, according to some studies.
Before and After Life
Quality assurance and environmental impact are two additional areas that have seen improvements. The process of evaluating and certifying LED performance has benefited from advancements in technology, helping to assuage end user questions about the reliability, performance, and environmental impact of individual diodes. This year, the National Institute of Standards and Technology, now a part of the U.S. Department of Commerce, began offering a faster, more accurate calibration service for assessing the brightness of LED lamps and other solid-state lighting products for lamp manufacturers. Lamps were previously calibrated with photometers, tools that measures brightness at all wavelengths while also considering the human eye's natural sensitivities to a range of colors. The NIST lab had been able to measure lamp brightness with reasonably low uncertainties—previously between 0.5% and 1.0%. Thanks to its revamps in equipment and processes—specifically upgrading to two automated equipment tables, one for the light sources and the other for the detectors—NIST has reduced the uncertainties to 0.2% or less.
The March 2019 article “Environmental and Energy Improvements of LED Lamps over Time: A Comparative Life Cycle Assessment” by researchers at the University of Portland, in Oregon, notes that newer LED lamps have a smaller environmental impact than past SSL technologies—and even more so when compared to conventional lighting technologies. Newer LED lamps are manufactured with less metals and thus produce less hazardous waste, all without compromising their efficacy. “Innovation in LEDs has continued to shape a new frontier in lighting, one that is moving faster than ever,” says co-author Heather Dillon, an associate professor of mechanical engineering. “New applications for consumers, like LEDs that connect to smart phones, are my favorite innovation. The challenge with the new and innovative products is the complexity of the devices, making end of life a concern for consumers. This is an opportunity for the LED developers to take a leadership role in how consumer electronics of the future are designed for recycle and reuse.”
Emerging LED Markets and Services
The accessibility to and on-demand capabilities of 3D printing have extended to SSL industry. Lighting designers and architects can now conceive luminaire assemblies with custom form factors specific to a project, and even manufacture them onsite, minimizing lead times. Additive manufacturing has also enabled the integration of heat sinks, critical for absorbing and dispersing excess heat away from the LED diode, directly in the design of the fixture envelope rather than appending them as an auxiliary component. These production capabilities can ultimately reduce the overall size and cost of a fixture while increasing its aesthetic appeal and enabling greater access to bespoke products.
While manufacturers have increased their focus on customization, architects, designers, and building owners continue to be drawn to LEDs’ ability to reduce energy consumption. But reliability and technological obsolescence continue to be concerns, particularly for end users. As a result, Dillon notes, several lighting manufacturers have begun offering “lighting as a service” contracts that guarantee specific lighting levels or features, and then take care of the confusion around the replacement process of lighting. “Researchers have been urging the designers and manufacturers to think about disassembly for repair and reuse for several years,” she says. This development “creates an opportunity for LEDs to maintain leadership in environmental stewardship.”
