As manufacturers strive for market share in the burgeoning LED lighting market each tries to outdo the other with ever-improving efficacy claims. But just how far can the LED chip makers go and how soon will they get there?
Equally important: LED cost is plummeting. Thanks to a phenomenon known as Haitz’s Law, LED cost is said to be falling by a factor of 10 every decade, while the light generated per package rises by a factor of 20.
Haitz’s law is an observation and forecast about the steady improvement, over many years, of light-emitting diodes (LED). It states that every decade, the cost per lumen (unit of useful light emitted) falls by a factor of 10, the amount of light generated per LED package increases by a factor of 20, for a given wavelength (color) of light. It is considered the LED counterpart to Moore’s law.
LED Efficacy Improvement Shows No Signs of Slowing article briefly explores the historical trend of improving efficacy of high-brightness LEDs, considers the theoretical efficiency limits, and takes a look at how contemporary devices stack up. Finally, the article takes a look at what manufacturers such as Cree and OSRAM are up to in their R&D labs to find out how tomorrow’s chips will perform. Rapid increases in LED efficacy show no sign of slowing just yet. And with a mainstream lighting market for LEDs potentially worth billions of dollars, manufacturers are not shy about pouring hundreds of millions into R&D.
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Tomi Engdahl says:
Osram in pilot production with GaN-on-silicon high-power LEDs
http://www.edn.com/blog/PowerSource/41561-Osram_in_pilot_production_with_GaN_on_silicon_high_power_LEDs.php
High-brightness LED prices have been dropping sharply even as their lumens/Watt has been increasing. Here’s a technology development that should serve to drive prices even lower, albeit we won’t see the results for at least two years: Osram has announced that it’s in the pilot stage of producing high-performance blue LEDs grown in gallium-nitride layers on 6-in. silicon wafers.
“Quality and performance data on the fabricated LED silicon chips match those of sapphire-based chips: …1 mm² chips driven at 350 mA. In combination with a conventional phosphor converter in a standard housing — in other words as white LEDs — these prototypes correspond to 140 lm at 350 mA with an efficiency of 127 lm/W at 4500K.”
Tomi Engdahl says:
Smaller, brighter LEDs can significantly cut LED bulb cost
http://www2.electronicproducts.com/Smaller_brighter_LEDs_can_significantly_cut_LED_bulb_cost-article-hlrc02_feb2012-html.aspx
Using silicon-carbide technology, XLamp XB-D series LEDs lay claim to having the smallest footprint (2.5 x 2.5 mm) for a lighting-class LED. Despite the small size, the LED provides high output; it produces up to 107 lm/W in warm white (3,000K) at 350 mA and a realistic operating junction temperature of 85°C.
The use of a silicon-carbide substrate (SiC) to grow gallium-nitride (GaN) LEDs provides a better lattice match between the two materials than when a silicon-on-saphire process is used, resulting in the production of more photons per unit area, or more light in less space, as well as higher efficacy.
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Tomi Engdahl says:
Cree ups lumens/Watt AND lumens/dollar with new LEDs
http://www.edn.com/blog/PowerSource/41609-Cree_ups_lumens_Watt_AND_lumens_dollar_with_new_LEDs.php
The XB-D series is optimized for price as well as performance, delivering twice the lumens per dollar of other LEDs. Today’s introduction, the XT-E LED, more than doubles the lumens per watt (LPW) of Cree’s existing XLamp XP-E LED family, providing up to 148 LPW at 85°C (or up to162 LPW at 25°C) in cool white (6000 K); or up to 114 lumens per watt in warm white (3000 K) at 85°C, both at 350 mA.
Tomi Engdahl says:
Cree claims R&D record for white LED: 254 lm/Watt
http://www.edn.com/blog/PowerSource/41719-Cree_claims_R_D_record_for_white_LED_254_lm_Watt.php?cid=EDNToday_20120412
Cree says that the R&D version of the white LED’s efficacy was measured at 254 lumens per watt, at a correlated color temperature of 4408 K at standard room temperature, 350 mA. In the past Cree has said it takes about a year for the R&D version of a device to go into generally available production quantities, so we can look for a commercial version in Q2 2013.
Cree’s previous record was 231 lm/Watt.
The device is built on a silicon carbide-based wafer technology that features advancements in LED chip architecture and phosphor
Tomi Engdahl says:
Silica Lighting – LED Street Lighting Demo
LED Street Lighting Demo based on TI’s Piccolo Processor and MOSFET Driver with Seoul Semiconductor Z5P.
http://www.silica.com/designers-community/video/video/silica_lighting_led_street_lighting_demo.html?page=0&hd=0&cHash=773cd8da131e16f837feda7920e341a0
Tomi Engdahl says:
Next week’s LightFair (aka LEDFair) promises newest in solid-state lighting
http://www.edn.com/blog/PowerSource/41754-Next_week_s_LightFair_aka_LEDFair_promises_newest_in_solid_state_lighting.php
Next week is the lighting industry’s pre-eminent trade show, LightFair, which to be as accurate as possible should change its name to LEDFair. The show fills up the massive Las Vegas Convention Center, and virtually every booth there is showing off LED-based lights. Which is a little strange because as it stands today, LEDs have very little penetration into the general lighting market.
Lighting isn’t like consumer electronics, susceptible to the whims of consumers who generally have very similar needs.
Building owners expect lighting systems to last for 10-20 years, so unless it’s a new construction, it’s not a slam dunk that a building owner is going to embrace a new LED-based light system. True, often (if all goes well) the payback in energy savings can make LED lights attractive, but unlike residential lighting, most commercial lighting already uses relatively efficient fluorescent lighting, so the payback may not be fast enough to pry a building owner’s wallet open.
Tomi Engdahl says:
Structural Defects Undermine LED Luminosity
http://www.digikey.com/us/en/techzone/lighting/resources/articles/structural-defects-undermine-led-luminosity.html
Gradual fading, which is the cause of failure for most LEDs, is primarily due to microcracks in the semiconductor die. These defects are introduced during the complex wafer manufacturing process.
Called threading dislocations, these microcracks multiply over time — more quickly when the LED is exposed to high temperatures — increasing the number of sites where the chip’s charge carriers can recombine without producing light.
However, the increase in this so-called “non-radiative recombination” is not the only mechanism that causes LEDs to fail. Threading dislocations also create paths for leakage currents, robbing the LED of yet more valuable charge carriers. The situation gets worse over time as defects multiply, leading to an increased risk of failure from power supply spikes or electrostatic discharge (ESD) events.
This article describes why leakage currents occur and suggests what can be done to slow the process of deterioration during the LED’s operational life, such that the chip delivers on the longevity these solid-state light sources promise.
Modern LEDs are impressive devices, but they have an Achilles Heel. Unavoidable tiny structural defects created during manufacture provide paths for charge carriers to escape without contributing to light output. These defects multiply over time, further reducing luminosity and, in the worst cases, causing premature failure.
LED manufacturers are experimenting with alternative manufacturing techniques and materials, and some have released products with fewer threading dislocations when new, but engineers are advised to incorporate adequate precautions into their designs to limit the inevitable effects of defects.
First, it is a good idea for the engineer to buy from a reputable distributor who stocks parts from the leading manufacturers. Second, the LED should be operated at the forward voltage recommended by the supplier using a good quality LED driver power supply from manufacturers such as Fairchild Semiconductor and Diodes, Inc. Third, the engineer should protect the chip from mechanical stress and exposure to ESD events. And fourth, it should come as no surprise for the engineer to learn that the LED should be adequately cooled.
Tomi Engdahl says:
GaN-on-GaN breakthrough LED boosts MR16 performance
http://www.edn.com/blog/PowerSource/41817-GaN_on_GaN_breakthrough_LED_boosts_MR16_performance.php
Despite the ever-improving light output from white LEDs, there are still some fundamental limitations in the current technology, which in general is based on either silicon carbide substrates (Cree) or sapphire substrates (just about everyone else). The active or light-emitting region in a white LED is formed by growing gallium nitride (GaN) on the substrate.
The problem with this approach is that the crystal lattice mismatch caused by the two different materials results in imperfections, and these imperfections in the LED reduce the amount of the light the device can produce.
A Fremont, CA start-up, Soraa, has developed the technology to grow GaN crystals on their native GaN substrate so that the active-GaN-region crystals grow with fewer imperfections and can accommodate higher power densities which, the company claims, allows the LED to emit 5-10 times more light from the same crystal area.
Soraa has an impeccable pedigree: One of its founders is Shuji Nakamura, who is credited with the discovery of p-type doping in GaN and thus the development of blue, green, and white LEDs.
Interestingly, the company’s first product is not an LED but rather a complete LED MR16 lamp.
This is where Soraa’s GaN-on-GaN-enabled 12V AC product family shines: Depending on the version, the product family
’s performance approaches that of generic 50W halogen lamps, including crisp shadows and similar CRI. The lamps include integral drivers that operate with several combinations of transformers and dimmers. The standard version is offered at either 2700K or 3000K and 80 CRI, and a high-CRI version is available at 95 CRI. To reach high color-rendering with deep red (R9>90) this version uses a violet-pumped triphosphor for a closer match to the blackbody than can be achieved with conventional blue-pumped two-phosphor technology.
Wilton Dupaty says:
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Tomi Engdahl says:
Solid-state lighting owes much to lone-wolf engineer
http://www.edn.com/electronics-blogs/powersource/4375587/Solid-state-lighting-owes-much-to-lone-wolf-engineer?cid=EDNToday
White LEDs are already illuminating handheld devices’ display backlighting and camera flashes. Within 5 years, the majority of lights within the US and much of the rest of the world will have shifted over from incandescent and fluorescent technology to solid-state: LEDs simply do a much better job of converting electrons to photons than incandescent lights and are longer-lasting than fluorescents.
Over the next twenty years, the DoE estimates (PDF) cumulative energy savings to total $250 billion at today’s energy prices and reduce greenhouse gas emissions by 1,800 million metric tons of carbon. This historic shift would not be possible without the development of a manufacturable intense blue LED light source.
LEDs have been around for a long time, dating back to the ‘70s when the first red LED watches and displays were sold. These low-power LEDs, initially red but soon including yellow, were indicator or display lights: they imparted information rather than illumination.
Shuji Nakamura, a young engineer with a master’s degree in engineering at Nichia, a relatively small Japanese company that made phosphors for fluorescent lights and CRT displays, was becoming increasingly frustrated with his lack of ability to create new products that his company could sell. He obediently developed the new products his salespeople told him the market needed, only to be blamed when they failed to sell.
Very well, he decided, if need be he would quit, but in the meantime he would work on projects that he personally believed to be important. And clearly being a proponent of finding a Big, Hairy, Audacious Goal, Nakamura decided to set as his goal the invention of the blue LED which had so far bedeviled researchers at companies and universities alike.
He got no support from his immediate boss
Deciding that he would have to go straight to the head of his company to get support, he walked into the founder of Nichia’s office one morning and said, “I want to develop a blue LED.”* To his surprise, he received permission to go ahead.
His lone quest to make a manufacturable gallium-nitride-based blue LED was ultimately successful. With the addition of a phosphor coating, Nakamura’s blue LED achieved the Holy Grail of solid state lighting – an intense solid-state white light source.
Tomi Engdahl says:
White LEDs Printed on Paper—A Doctoral Thesis—Part I
http://www.edn.com/design/led/4391796/White-LEDs-Printed-on-Paper-A-Doctoral-Thesis-Part-I?cid=Newsletter+-+EDN+Today
One-dimensional (1-D), zinc oxide (ZnO) and copper (II) oxide (CuO), nanostructures have great potential for applications in the fields of optoelectronic and sensor devices. Research on nanostructures is a fascinating field that has evolved during the last few years especially after the utilization of the hydrothermal growth method. Using this method variety of nanostructures can be grown from solutions, it is a cheap, easy, and environment friendly approach. These nanostructures can be synthesized on various conventional and nonconventional substrates such as silicon, plastic, fabrics and paper etc.
The primary purpose of the work presented in this thesis is to realize controllable growth of ZnO, CuO and nanohybrid ZnO/CuO nanostructures and to process and develop white light emitting diodes and sensor devices from the corresponding nanostructures.
Tomi says:
Re-packaged LEDs offer improved performances
Researchers take unconventional approach to improving technology
http://www2.electronicproducts.com/Re_packaged_LEDs_offer_improved_performances-article-fajb_better_performing_LEDs_sep2012-html.aspx
While many researchers have taken the approach of trying to improve upon the technology behind a light emitting diode, a group of researchers from Taiwan have taken the rather unorthodox approach of tackling the technology’s packaging instead, to see if a solution might be found there instead.
The group’s study focuses on a design called a “flip glass substrate” which demonstrates improvements in terms of a wider viewing angle and better color uniformity. What’s more, it also offers developers the chance to identify at an earlier stage any flaws within the LED itself, as compared to other LED packaging methods.
You see, the standard LED nowadays is packaged in plastic leaded chip carriers, printed circuit boards, ceramic holders, or other somewhat different, though relatively similar materials. A good majority of these packages are partly non-transparent, which means that the LED light cannot penetrate the side wall.
Tomi Engdahl says:
How Lasers Inspired the Inventor of the LED
http://www.wired.com/design/2012/10/holonyak-laser-led-inventor/
In 1962, 50 years ago today, Nick Holonyak Jr. and his team at GE invented the Light Emitting Diode. While LED lights are almost everywhere today — from bridges to headlights to keychain flashlights that are brighter than the sun — their initial development was ripe with uncertainty and competitive research. A direct result of another groundbreaking technology of its day, the laser, LEDs have continued to evolve and now illuminate our homes and transmit our data.
Wired Design caught up with Holonyak, now a professor at the University of Illinois, to ask him about the history, and future, of LEDs.
Tomi Engdahl says:
Fish skin points to better LEDs
Scaly secret to camouflage, and that’s no red herring
http://www.theregister.co.uk/2012/10/21/fish_skin_photonics/
A trick of the light evolved by silvery fish to avoid predators could help improve optical devices like LEDs, according to a study in Nature Photonics.
The research took a look at how fish such as sardines and herring reflect light without polarising it.
these fish avoid reflecting polarised light by having two types of reflective crystals in their skins.
In photonics, this property could be used to make more efficient low-loss devices and brighter LED lamps, the researchers say.
Tomi Engdahl says:
Cree Introduces 200 Lumen/Watt Production Power LEDs
http://news.slashdot.org/story/12/12/30/0338234/cree-introduces-200-lumenwatt-production-power-leds
“Cree just announced production power LEDs reaching 200 lumen/watt. Approximately doubling the previous peak LED light efficiency, the new LEDs will require less cooling. This should enable the MK-R series to finally provide direct no-hassle replacements to popular form-factors such as MR-16 spots and incandescent lighting in general.”
Tomi Engdahl says:
Cree Reaches LED Industry Milestone with 200 Lumen-Per-Watt LED
http://www.cree.com/news-and-events/cree-news/press-releases/2012/december/mkr-intro
The new MK-R LEDs make the next generation of 100+ lumens-per-watt system possible for high-lumen applications, including outdoor and indoor directional applications, such as halogen replacement lamps. MK-R LEDs are available in EasyWhite® color temperatures, providing the LED industry’s best color consistency for designs that use only one LED. For systems that use multiple LEDs, MK-R enables manufacturers to use fewer LEDs while still maintaining light output and quality, which translates to lower system cost.
Tomi Engdahl says:
Infrared chip yields 72% efficiency
http://www.edn.com/electronics-products/other/4403643/Infrared-chip-yields-72–efficiency?cid=Newsletter+-+EDN+Weekly
A record-setting 1mm2 infrared chip prototype from Osram Opto Semiconductor broke through a barrier by achieving an efficiency of up to 72% at 100 milliamps using thin-film technology. Under laboratory conditions at 930 milliwatts from an operating current of 1 amp, its light output is 25% higher than currently available solutions.
The 850-nanometer wavelength is ideal for infrared illumination such as for surveillance tasks and CCTV camera applications.
The chip is expected to be in production in mid-2013
Tomi Engdahl says:
Fireflies bring us brighter LEDs
http://www.gizmag.com/fireflies-led-lights/25702/
Fireflies … they’ve allowed us to image the bloodstream and they’ve inspired the creation of a light that could run on waste. Now, they’ve helped an international team of scientists get over 50 percent more light out of existing LED bulbs. The secret lies in the insects’ scales.
More specifically, the secret lies in the scales of the Photuris firefly.
In all types of fireflies, their bioluminescence is emitted through the cuticle of their exoskeleton.
It was discovered that in the Photuris genus, however, scales in the cuticle possessed optical qualities that boosted the amount of light that could get through. These qualities were concentrated along the jagged edges of the roof-shingle-like scales.
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Tomi Engdahl says:
Today’s LEDs—What’s responsible for the improvements?
http://www.edn.com/design/led/4414325/Today-s-LEDs-What-s-responsible-for-the-improvements-
Traditionally LEDs were viewed as an excellent lighting alternative offering significant energy savings, albeit with inferior visual performance compared to some lighting options.
Over the past few years, the energy savings LEDs provide have continued to grow at an impressive pace. In fact today´s LEDs are more than twice as efficient as LEDs from just five years ago, offering 25-30% energy savings compared to CCFLs and up to 80% savings compared to incandescent bulbs. These eye-catching energy savings have been accompanied by significant space savings and enhanced visual performance.
Key developments in LED manufacturing, specifically enhanced equipment, improved processes and superior materials, have allowed the latest generation of LEDs to provide a powerful combination of excellent light output, visual performance and space savings. Let’s look at each development closer.
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Tomi Engdahl says:
Efficiency Greater Than 100%? Yes, Sort Of
http://www.eetimes.com/author.asp?section_id=36&doc_id=1325379&
Contrary to our normal expectations, LEDs can exhibit optical efficiencies well above 100%–but only if you re-define “input power” in a unique way.
I am a firm believer in the laws of thermodynamics and their plain-spoken corollary, “When it comes to energy, there is no free lunch.” That’s why I automatically dismiss any article or ad promising efficiency of 100% or better
That’s why I was shocked when I saw the headline “8000% efficient LED enables ultralow-power data transmission” in a recent article in Laser Focus World.
It turns out, though, that the headline was correct. The improved efficiency has to do with how and where you measure input and output powers, plus the subtleties of LEDs and quantum mechanics. To quote the start of the article:
Certain LEDs, when heated and then run at a very low power, exhibit wall-plug efficiencies [electrical-to-optical power-conversion efficiency] of more than 100%; this effect is explained by the existence of thermoelectric pumping of the LED… The setup transmitted 3 kbit/sec at a bit-error rate of 3 x 10-3 and an energy expenditure per bit of only 40 fJ.
Roughly speaking, the LED is pumped with thermal energy in advance, then the energy is parceled out via optical data bits, while the LED itself does not need to consume additional corresponding power. (This effect goes by several names: electro-luminescent or EL cooling, electroluminescent refrigeration, thermophotonic cooling, and optothermionic refrigeration.)