Tag Archives: letter-dd-tech

Use of copper as a fluorescent material allows for the manufacture of inexpensive and environmentally compatible organic light-emitting diodes (OLEDs). Thermally activated delayed fuorescence (TADF) ensures high light yield. Scientists of Karlsruhe Institute of Technology (KIT), CYNORA, and the University of St Andrews have now measured the underlying quantum mechanics phenomenon of intersystem crossing in a copper complex. The results of this fundamental work are reported in the Science Advances journal and contribute to enhancing the energy efficiency of OLEDs.

Organic light-emitting diodes are deemed tomorrow’s source of light. They homogeneously emit light in all observation directions and produce brilliant colors and high contrasts. As it is also possible to manufacture transparent and flexible OLEDs, new application and design options result, such as flat light sources on window panes or displays that can be rolled up. OLEDs consist of ultra-thin layers of organic materials, which serve as emitter and are located between two electrodes. When voltage is applied, electrons from the cathode and holes (positive charges) from the anode are injected into the emitter, where they form electron-hole pairs. These so-called excitons are quasiparticles in the excited state. When they decay into their initial state again, they release energy.

Excitons may assume two different states: Singlet excitons decay immediately and emit light, whereas triplet excitons release their energy in the form of heat. Usually, 25 percent singlets and 75 percent triplets are encountered in OLEDs. To enhance energy efficiency of an OLED, also triplet excitons have to be used to generate light. In conventional light-emitting diodes heavy metals, such as iridium and platinum, are added for this purpose. But these materials are expensive, have a limited availability, and require complex OLED production methods.

It is cheaper and environmentally more compatible to use copper complexes as emitter materials. Thermally activated delayed fluorescence (TADF) ensures high light yields and, hence, high efficiency: Triplet excitons are transformed into singlet excitons which then emit photons. TADF is based on the quantum mechanics phenomenon of intersystem crossing (ISC), a transition from one electronic excitation state to another one of changed multiplicity, i.e. from singlet to triplet or vice versa. In organic molecules, this process is determined by spin-orbit coupling. This is the interaction of the orbital angular momentum of an electron in an atom with the spin of the electron. In this way, all excitons, triplets and singlets, can be used for the generation of light. With TADF, copper luminescent material reaches an efficiency of 100 percent.

Stefan Bräse and Larissa Bergmann of KIT’s Institute of Organic Chemistry (IOC), in cooperation with researchers of the OLED technology company CYNORA and the University of St Andrews, United Kingdom, for the first time measured the speed of intersystem crossing in a highly luminescent, thermally activated delayed fluorescence copper(I) complex in the solid state. The results are reported in the Science Advances journal. The scientists determined a time constant of intersystem crossing from singlet to triplet of 27 picoseconds (27 trillionths of a second). The reverse process – reverse intersystem crossing – from triplet to singlet is slower and leads to a TADF lasting for an average of 11.5 microseconds. These measurements improve the understanding of mechanisms leading to TADF and facilitate the specific development of TADF materials for energy-efficient OLEDs.

Whether showing off family photos on smartphones or watching TV shows on laptops, many people look at liquid crystal displays (LCDs) every day. LCDs are continually being improved, but almost all currently use color technology that fades over time. Now, a team reports in ACS Nano that using aluminum nanostructures could provide a vivid, low-cost alternative for producing digital color.

Conventional color technology used in displays is susceptible to photobleaching, or fading. So researchers have looked toward aluminum nanoparticles that can display colors in electronics, thanks to a property called ‘plasmon resonance.’ To create plasmonic color devices, researchers group nanostructures into arrays called pixels. Color is generated by scattering light onto the pixels, with different arrangements creating different colors. Aluminum plasmonic pixels are advantageous for use in electronic displays because they are inexpensive and can be made in an ultrasmall size, which can increase image resolution. But these pixels create muted and dull colors. In a recent publication, Stephan Link and colleagues developed a method that allows the red end of the color spectrum to be more vibrant. Now, the same team reports another approach that makes the blue end of the spectrum much more brilliant, too.

The researchers used a three-step design approach to create aluminum nanostructure pixels that exploit ‘Fano interference’ — an interaction between the plasmon resonance and the pixel’s array structure — to produce vibrant blue-end colors. Combining their previous research with this new development, the team was able to create pixels with extremely vivid colors across the entire visible spectrum. The researchers then incorporated a set of red, green and blue pixels into a liquid crystal display that could be electrically turned on and off, demonstrating this work’s potential use in commercial flat-panel displays.

CEA-Leti, an applied-research institute for microelectronics, will demonstrate at CES 2016 three disruptive innovations, ranging from ultra-high-brightness, augmented-reality glasses to extremely high-speed wireless data transmission between mobile devices, and the world’s first TV white-space modem limiting interference in adjacent spectrum bands.

The three demonstrations at Eureka Park in the Sands hotel mark Leti’s first formal participation at CES, and reflect the institute’s growing focus on applied technologies for consumer market solutions.

The demonstrators include:

  • DiamonDisplay,the world’s brightest augmented-reality display with the first demonstrator of a high-density micro-LED array that is scalable to a standard microelectronic large-scale fabrication process. This micro-LED display provides brightness that is 100 to 1,000 times higher than current micro displays, enables very high definition, very sharp contrast in daylight and is ideal for compact, lighter products that consume less power.
  • G-Link, a low-power, wireless connection that enables ultra-high-speed transfer of gigabits of data between two devices a few centimeters apart. For consumers it provides a wireless connection between two mobile devices to share, for example, HD videos, between a movie camera and a video display, or between a kiosk and a tablet to download HD videos, etc. G-Link uses a very compact and low-cost package, integrating the entire system, including antennas.  The second generation will be available in 2016 and will provide increased data rate (5Gbps) at lower power consumption (50mW).
  • TV White Space modem, the world’s first wide-area, wireless technology based on the IEEE 1900.7 standard, providinghigh-speed Internet service over long-distances from just one access point. Leti’s demonstration shows a new wireless-network solution that uses adjacent spectrum bands to provide broad coverage indoors and out: up to 64km range in open spaces. The technology can help reduce the digital divide by providing broadband access in underserved rural areas.

“Leti is well known in the industry as a strategic partner for companies that come to us to help them apply tomorrow’s microelectronic technologies in their products, ranging from consumer markets to biotech, security, transportation and the Internet of Things,” said Leti CEO Marie Semeria. “But we also encourage our teams to imagine how our expertise can enhance consumers’ quality of like. This focus on innovation is a pillar of Leti’s successful startup program, and these demonstrators provide a sample of the results.”

Three recent Leti startups also will demonstrate technologies at Eureka Park:

  • Aryballe Technologies will show the diversity of its biochemical sensors in a universal detector able to identify several thousand odors listed in olfactory-signature databases. Its first product is a portable odor-detection device, Neosmia, for people with smell disorders. Booth # 81234.
  • eLichens develops services and miniaturized sensors for consumers and professionals to detect, monitor and predict air quality. The sensors continuously measure the CO, CO2 or CH4 values in local ambient air. Booth # 81233.
  • The AirBoard is an Arduino-compatible, wireless, open-source computer for rapidly prototyping smart connected objects for the Internet of Things. Booth # 81232.

Leti has launched more than 50 startups over the years. These include Movea, the motion-sensing company that was acquired by InvenSense; iskn, a digitized sketching-tool provider, and BeSpoon, whose tracking chips use cell phones to locate within a few centimeters common items such as keys, even from hundreds of meters away.

BeSpoon and EnerBee, a Leti startup that specializes in motion-based energy harvesting, also will exhibit in Eureka Park.

Leti will be part of the French Tech delegation at CES and will be one of 34 participants in Minalogic’s first joint collective mission of the new region Auvergne Rhône-Alpes.

Leti’s team will be available to discuss the demonstrators and provide more information on the institute and its startup program at booth # 81333 in Eureka Park.

A new method for building “drawbridges” between metal nanoparticles may allow electronics makers to build full-color displays using light-scattering nanoparticles that are similar to the gold materials that medieval artisans used to create red stained-glass.

“Wouldn’t it be interesting if we could create stained-glass windows that changed colors at the flip of a switch?” said Christy Landes, associate professor of chemistry at Rice and the lead researcher on a new study about the drawbridge method that appears this week in the open-access journal Science Advances.

The research by Landes and other experts at Rice University’s Smalley-Curl Institute could allow engineers to use standard electrical switching techniques to construct color displays from pairs of nanoparticles that scatter different colors of light.

For centuries, stained-glass makers have tapped the light-scattering properties of tiny gold nanoparticles to produce glass with rich red tones. Similar types of materials could increasingly find use in modern electronics as manufacturers work to make smaller, faster and more energy-efficient components that operate at optical frequencies.

Though metal nanoparticles scatter bright light, researchers have found it difficult to coax them to produce dramatically different colors, Landes said.

Rice’s new drawbridge method for color switching incorporates metal nanoparticles that absorb light energy and convert it into plasmons, waves of electrons that flow like a fluid across a particle’s surface. Each plasmon scatters and absorbs a characteristic frequency of light, and even minor changes in the wave-like sloshing of a plasmon shift that frequency. The greater the change in plasmonic frequency, the greater the difference between the colors observed.

“Engineers hoping to make a display from optically active nanoparticles need to be able to switch the color,” Landes said. “That type of switching has proven very difficult to achieve with nanoparticles. People have achieved moderate success using various plasmon-coupling schemes in particle assemblies. What we’ve shown though is variation of the coupling mechanism itself, which can be used to produce huge color changes both rapidly and reversibly.”

To demonstrate the method, Landes and study lead author Chad Byers, a graduate student in her lab, anchored pairs of gold nanoparticles to a glass surface covered with indium tin oxide (ITO), the same conductor that’s used in many smartphone screens. By sealing the particles in a chamber filled with a saltwater electrolyte and a silver electrode, Byers and Landes were able form a device with a complete circuit. They then showed they could apply a small voltage to the ITO to electroplate silver onto the surface of the gold particles. In that process, the particles were first coated with a thin layer of silver chloride. By later applying a negative voltage, the researchers caused a conductive silver “drawbridge” to form. Reversing the voltage caused the bridge to withdraw.

“The great thing about these chemical bridges is that we can create and eliminate them simply by applying or reversing a voltage,” Landes said. “This is the first method yet demonstrated to produce dramatic, reversible color changes for devices built from light-activated nanoparticles.”

Byers said his research into the plasmonic behavior of gold dimers began about two years ago.

“We were pursuing the idea that we could make significant changes in optical properties of individual particles simply by altering charge density,” he said. “Theory predicts that colors can be changed just by adding or removing electrons, and we wanted to see if we could do that reversibly, simply by turning a voltage on or off.”

The experiments worked. The color shift was observed and reversible, but the change in the color was minute.

“It wasn’t going to get anybody excited about any sort of switchable display applications,” Landes said.

But she and Byers also noticed that their results differed from the theoretical predictions.

Landes said that was because the predictions were based upon using an inert electrode made of a metal like palladium that isn’t subject to oxidation. But silver is not inert. It reacts easily with oxygen in air or water to form a coat of unsightly silver oxide. This oxidizing layer can also form from silver chloride, and Landes said that is what was occurring when the silver counter electrode was used in Byers’ first experiments.

“It was an imperfection that was throwing off our results, but rather than run away from it, we decided to use it to our advantage,” Landes said.

Rice plasmonics pioneer and study co-author Naomi Halas, director of the Smalley-Curl Institute, said the new research shows how plasmonic components could be used to produce electronically switchable color-displays.

“Gold nanoparticles are particularly attractive for display purposes,” said Halas, Rice’s Stanley C. Moore Professor of Electrical and Computer Engineering and professor of chemistry, bioengineering, physics and astronomy, and materials science and nanoengineering. “Depending upon their shape, they can produce a variety of specific colors. They are also extremely stable, and even though gold is expensive, very little is needed to produce an extremely bright color.”

In designing, testing and analyzing the follow-up experiments on dimers, Landes and Byers engaged with a brain trust of Rice plasmonics experts that included Halas, physicist and engineer Peter Nordlander, chemist Stephan Link, materials scientist Emilie Ringe and their students, as well as Paul Mulvaney of the University of Melbourne in Australia.

Together, the team confirmed the composition and spacing of the dimers and showed how metal drawbridges could be used to induce large color shifts based on voltage inputs.

Nordlander and Hui Zhang, the two theorists in the group, examined the device’s “plasmonic coupling,” the interacting dance that plasmons engage in when they are in close contact. For instance, plasmonic dimers are known to act as light-activated capacitors, and prior research has shown that connecting dimers with nanowire bridges brings about a new state of resonance known as a “charge-transfer plasmon,” which has its own distinct optical signature.

“The electrochemical bridging of the interparticle gap enables a fully reversible transition between two plasmonic coupling regimes, one capacitive and the other conductive,” Nordlander said. “The shift between these regimes is evident from the dynamic evolution of the charge transfer plasmon.”

Halas said the method provides plasmonic researchers with a valuable tool for precisely controlling the gaps between dimers and other multiparticle plasmonic configurations.

“In an applied sense, gap control is important for the development of active plasmonic devices like switches and modulators, but it is also an important tool for basic scientists who are conducting curiosity-driven research in the emerging field of quantum plasmonics.”

Scientists and engineers are engaged in a global race to make new materials that are as thin, light and strong as possible. These properties can be achieved by designing materials at the atomic level, but they are only useful if they can leave the carefully controlled conditions of a lab.

Researchers at the University of Pennsylvania have now created the thinnest plates that can be picked up and manipulated by hand.

Even though they are less than 100 nanometers thick, the researchers’ plates are strong enough to be picked up by hand and retain their shape after being bent and squeezed. Credit: University of Pennsylvania

Despite being thousands of times thinner than a sheet of paper and hundreds of times thinner than household cling wrap or aluminum foil, their corrugated plates of aluminum oxide spring back to their original shape after being bent and twisted.

Like cling wrap, comparably thin materials immediately curl up on themselves and get stuck in deformed shapes if they are not stretched on a frame or backed by another material.

Being able to stay in shape without additional support would allow this material, and others designed on its principles, to be used in aviation and other structural applications where low weight is at a premium.

The study was led by Igor Bargatin, the Class of 1965 Term Assistant Professor of Mechanical Engineering and Applied Mechanics in Penn’s School of Engineering and Applied Science, along with lab member Keivan Davami, a postdoctoral scholar, and Prashant Purohit, an associate professor of mechanical engineering. Bargatin lab members John Cortes and Chen Lin, both graduate students; Lin Zhao, a former student in Engineering’s nanotechnology master’s program; and Eric Lu and Drew Lilley, undergraduate students in the Vagelos Integrated Program in Energy Research, also contributed to the research.

They published their findings in the journal Nature Communications.

“Materials on the nanoscale are often much stronger than you’d expect, but they can be hard to use on the macroscale” Bargatin said. “We’ve essentially created a freestanding plate that has nanoscale thickness but is big enough to be handled by hand. That hasn’t been done before.”

Graphene, which can be as thin as a single atom of carbon, has been the poster-child for ultra-thin materials since it’s discovery won the Nobel Prize in Physics in 2010. Graphene is prized for its electrical properties, but its mechanical strength is also very appealing, especially if it could stand on its own. However, graphene and other atomically thin films typically need to be stretched like a canvas in a frame, or even mounted on a backing, to prevent them from curling or clumping up on their own.

“The problem is that frames are heavy, making it impossible to use the intrinsically low weight of these ultra-thin films,” Bargatin said. “Our idea was to use corrugation instead of a frame. That means the structures we make are no longer completely planar, instead, they have a three-dimensional shape that looks like a honeycomb, but they are flat and contiguous and completely freestanding.”

“It’s like an egg carton, but on the nanoscale,” said Purohit.

The researchers’ plates are between 25 and 100 nanometers thick and are made of aluminum oxide, which is deposited one atomic layer at a time to achieve precise control of thickness and their distinctive honeycomb shape.

“Aluminum oxide is actually a ceramic, so something that is ordinarily pretty brittle,” Bargatin said. “You would expect it, from daily experience, to crack very easily. But the plates bend, twist, deform and recover their shape in such a way that you would think they are made out of plastic. The first time we saw it, I could hardly believe it.”

Once finished, the plates’ corrugation provides enhanced stiffness. When held from one end, similarly thin films would readily bend or sag, while the honeycomb plates remain rigid. This guards against the common flaw in un-patterned thin films, where they curl up on themselves.

This ease of deformation is tied to another behavior that makes ultra-thin films hard to use outside controlled conditions: they have the tendency to conform to the shape of any surface and stick to it due to Van der Waals forces. Once stuck, they are hard to remove without damaging them.

Totally flat films are also particularly susceptible to tears or cracks, which can quickly propagate across the entire material.

“If a crack appears in our plates, however, it doesn’t go all the way through the structure,” Davami said. “It usually stops when it gets to one of the vertical walls of the corrugation.”

The corrugated pattern of the plates is an example of a relatively new field of research: mechanical metamaterials. Like their electromagnetic counterparts, mechanical metamaterials achieve otherwise impossible properties from the careful arrangement of nanoscale features. In mechanical metamaterials’ case, these properties are things like stiffness and strength, rather than their ability to manipulate electromagnetic waves.

Other existing examples of mechanical metamaterials include “nanotrusses,” which are exceptionally lightweight and robust three-dimensional scaffolds made out of nanoscale tubes. The Penn researchers’ plates take the concept of mechanical metamaterials a step further, using corrugation to achieve similar robustness in a plate form and without the holes found in lattice structures.

That combination of traits could be used to make wings for insect-inspired flying robots, or in other applications where the combination of ultra-low thickness and mechanical robustness is critical.

“The wings of insects are a few microns thick, and can’t thinner because they’re made of cells,” Bargatin said. “The thinnest man-made wing material I know of is made by depositing a Mylar film on a frame, and it’s about half a micron thick. Our plates can be ten or more times thinner than that, and don’t need a frame at all. As a result, they weigh as little as than a tenth of a gram per square meter.”

Engineers at Oregon State University have made a fundamental breakthrough in understanding the physics of photonic “sintering,” which could lead to many new advances in solar cells, flexible electronics, various types of sensors and other high-tech products printed onto something as simple as a sheet of paper or plastic.

Sintering is the fusing of nanoparticles to form a solid, functional thin-film that can be used for many purposes, and the process could have considerable value for new technologies.

Photonic sintering has the possible advantage of higher speed and lower cost, compared to other technologies for nanoparticle sintering.

In the new research, OSU experts discovered that previous approaches to understand and control photonic sintering had been based on a flawed view of the basic physics involved, which had led to a gross overestimation of product quality and process efficiency.

Based on the new perspective of this process, which has been outlined in Nature Scientific Reports, researchers now believe they can create high quality products at much lower temperatures, at least twice as fast and with 10 times more energy efficiency.

Removing constraints on production temperatures, speed and cost, the researchers say, should allow the creation of many new high-tech products printed onto substrates as cheap as paper or plastic wrap.

“Photonic sintering is one way to deposit nanoparticles in a controlled way and then join them together, and it’s been of significant interest,” said Rajiv Malhotra, an assistant professor of mechanical engineering in the OSU College of Engineering. “Until now, however, we didn’t really understand the underlying physics of what was going on. It was thought, for instance, that temperature change and the degree of fusion weren’t related – but in fact that matters a lot.”

With the concepts outlined in the new study, the door is open to precise control of temperature with smaller nanoparticle sizes. This allows increased speed of the process and high quality production at temperatures at least two times lower than before. An inherent “self-damping” effect was identified that has a major impact on obtaining the desired quality of the finished film.

“Lower temperature is a real key,” Malhotra said. “To lower costs, we want to print these nanotech products on things like paper and plastic, which would burn or melt at higher temperatures. We now know that is possible, and how to do it. We should be able to create production processes that are both fast and cheap, without a loss of quality.”

Products that could evolve from the research, Malhotra said, include solar cells, gas sensors, radiofrequency identification tags, and a wide range of flexible electronics. Wearable biomedical sensors could emerge, along with new sensing devices for environmental applications.

In this technology, light from a xenon lamp can be broadcast over comparatively large areas to fuse nanoparticles into functional thin films, much faster than with conventional thermal methods. It should be possible to scale up the process to large manufacturing levels for industrial use.

This advance was made possible by a four-year, $1.5 million National Science Foundation Scalable Nanomanufacturing Grant, which focuses on transcending the scientific barriers to industry-level production of nanomaterials. Collaborators at OSU include Chih-hung Chang, Alan Wang and Greg Herman.

OSU researchers will work with two manufacturers in private industry to create a proof-of-concept facility in the laboratory, as the next step in bringing this technology toward commercial production.

By Sue Davis, Director of Business Development & Senior Analyst, Techcet

IDTechEx Printed Electronics USA 2015, held in Santa Clara, CA Nov 18-19, is one mega conference with 8 co-located tracks ranging from sensor technology & wearables to IoT, energy harvesting & storage to electric vehicles, 3D printing and graphene. IDTechEx completely occupied the Santa Clara Convention Center; throughout the day attendees and exhibitors commented attendance was up over prior years. To the dismay of some late arrivals, parking spaces were at a premium.

A venue with >200 exhibitors showcasing new technologies and applications connected conference attendees with equipment and materials suppliers, OEMs, end users, research institutes and academia.

Raghu Das, CEO of IDTechEx, kicked off the conference by sharing a key trends including:

  • Structural electronics are here now!
  • The Fashion industry is converging with technology (and evidenced by a number of exhibitors from this sector)
  • Stretchable electronics R&D has ramped significantly in the last 12 months
  • Printed and flexible electronics manufacturing is becoming center stage

Dr. Mounir Zok, a keynote speaker and biomedical engineering specialist for the US Olympic committee started his talk with a quote “The blink of an eye dictates gold vs no medal.” He emphasized that technology is a key enabler to continually improve sports performance.

Highlights from exhibitors and speakers follow.

Keith McMillen, founder and CEO of BeBop Sensors and avid musician, shared his journey of developing smart fabric cylindrical sensors to analyze a violinist’s bow movement led to utilizing this technology for the Internet of Things and the founding of BeBop Sensors.

BeBop Sensor Examples

BeBop Sensor Examples

Dream car in every facet; aesthetics, functionality and environmental impact understates the design of the Blade Car. Keith Czinger, CEO and Founder of Divergent discussed the foundation for Blade’s development was deeply rooted in reducing environmental impact while ensuring high performance. Divergent reports that manual chassis assembly can be completed within 30 minutes utilizing its’ node network. Nodes are manufactured of a metal alloy and produced using 3D printers. The light and strong chassis is comprised of these nodes and with carbon fiber tubes.

Divergent Blade utilizing 3D printing for node-tube chassis

Divergent Blade utilizing 3D printing for node-tube chassis

Printed Circuit Boards (PCBs) manufactured via additive 3D printing technology, vs. conventional processing labor, material and time intensive processes was demonstrated at NanoDimension’s booth. Simon Fried, CMO and Co-Founder of NanoDimension discussed the benefit of 3D printed circuit boards (prototyping in hours vs weeks, design flexibility, process repeatability, …). In addition to development the DragonFly 3D printer, NanoDimension has developed a line of specialty conductive inks.

NanoDimension DragonFly 200 3D Printer

NanoDimension DragonFly 200 3D Printer

Sensoria Fitness has developed a line of wear fitness clothing and integrated running system that communicates with iOS and Android apps. A key use case is the gait analysis capability to assist with performance running and to assist clinicians with treatment plans for dysfunctional gait patterns.

Sensoria Fitness Socks (Innovation Awards at CES 2015 & IDTechEx 2015 USA)

Sensoria Fitness Socks (Innovation Awards at CES 2015 & IDTechEx 2015 USA)

View Technologies, a joint venture between Stanley Black & Decker, Inc. and RF Controls, has developed the inView Platform that enables 3rd party applications to run more efficiently and accurately. This platform is comprised of Echo antenna(s) and three tiers of service that allow you Locate, Track and Act depending on business needs. Location service provide as real-time stream of 3D position data for Passive UHF RFID tags.

View Technologies - Manufacturing Application

View Technologies – Manufacturing Application

Valencell develops high-performance biometric sensor technology and licenses its technology to a variety of consumer electronics manufacturers, mobile device and accessory makers, sports and fitness brands, gaming companies, and first-responder/military suppliers for integration into their products.

Products utilizing Valencell’s Biometric Sensor Technolgy

Products utilizing Valencell’s Biometric Sensor Technolgy

Another show highlight was Demonstration Street, a dedicated area on the show floor for product demonstrations in various stages of development – prototype to commercialization- featured printed flexible displays including posters, e-readers, audio paper, interactive games, OLED displays, electronics in fabrics, interactive printed controls and menus, printed RFID and more.

IDTechEx 2015 USA offered a myriad of opportunities to interact with technologists and exhibitors attend hundreds of insightful presentations. Master classes covering an array of topics and company tours bookended the two-day conference and exhibition. The main challenge was to create a “show plan” in hopes that one would be able to attend desired presentations and exhibits.

Baltimore, MD — November 11, 2015 — Pixelligent, a leader in high-index advanced materials, today launched a new family of PixClear® materials for display and optical components and films. The PixClear product line is now available in a new solvent system — a low boiling ethyl acetate (ETA) — that delivers the same high performance while easing integration with customer manufacturing processes. Now leading manufacturing companies will have the choice of a standard, high boiling propylene glycol methyl ether acetate (PGMEA) or the low boiling ETA for their testing. These materials are available in both 20 percent and 50 percent loadings for PixClear PG and PixClear PB.

“The launch of our new PixClear ETA materials is a response to customer demand. These low boiling ETA dispersions will result in brighter, clearer devices produced at a lower cost, which directly supports reducing time to innovation for our customers in the display and adhesives space,” said Craig Bandes, President and CEO of Pixelligent. “At Pixelligent, we continue to expand our matrix of high quality, high-index nanomaterials in order to support the growth of our customers.” Matt Healy, Vice President of Product Management adds, “In August, we launched a full OLED materials family, which includes four products for testing internal light extraction structures for OLED lighting. All totaled, we have introduced 12 new products for customer testing in the past three months.”

PixClear zirconia dispersions are now available for order in two solvents, and at two different loadings, to complement the processes used for the production of displays and optical components.

WEST LAFAYETTE, Ind. — Silver nanowires hold promise for applications such as flexible displays and solar cells, but their susceptibility to damage from highly energetic UV radiation and harsh environmental conditions has limited their commercialization.

New research suggests wrapping the nanowires with an ultrathin layer of carbon called graphene protects the structures from damage and could represent a key to realizing their commercial potential.

“We show that even if you have only a one-atom-thickness material, it can protect from an enormous amount of UV radiation damage,” said Gary Cheng, an associate professor of industrial engineering at Purdue University.

The lower images depict how graphene sheathing protects nanowires even while being subjected to 2.5 megawatts of energy intensity per square centimeter from a high-energy laser, an intensity that vaporizes the unwrapped wires. The upper images depict how the unwrapped wires are damaged with an energy intensity as little as .8 megawatts per square centimeter. (Purdue University image)

The lower images depict how graphene sheathing protects nanowires even while being subjected to 2.5 megawatts of energy intensity per square centimeter from a high-energy laser, an intensity that vaporizes the unwrapped wires. The upper images depict how the unwrapped wires are damaged with an energy intensity as little as .8 megawatts per square centimeter. (Purdue University image)

Devices made from silver nanowires and graphene could find uses in solar cells, flexible displays for computers and consumer electronics, and future “optoelectronic” circuits for sensors and information processing. The material is flexible and transparent, yet electrically conductive, and is a potential replacement for indium tin oxide, or ITO. Industry is seeking alternatives to ITO because of drawbacks: It is relatively expensive due to limited abundance of indium, and it is inflexible and degrades over time, becoming brittle and hindering performance, said Suprem Das, a former Purdue doctoral student and now a postdoctoral researcher at Iowa State University and The Ames Laboratory.

However, a major factor limiting commercial applications for silver nanowires is their susceptibility to harsh environments and electromagnetic waves.

“Radiation damage is widespread,” said Das, who led the work with Purdue doctoral student Qiong Nian (pronounced Chung Nee-an). “The damage occurs in medical imaging, in space applications and just from long-term exposure to sunlight, but we are now seeing that if you wrap silver nanowires with graphene you can overcome this problem.”

Findings appeared in October in the journal ACS Nano, published by the American Chemical Society. The paper was authored by Das; Nian; graduate students Mojib Saei, Shengyu Jin and Doosan Back; previous postdoctoral research associate Prashant Kumar; David B. Janes, a professor of electrical and computer engineering; Muhammad A. Alam, the Jai N. Gupta Professor of Electrical and Computer Engineering; and Cheng.

Raman spectroscopy was performed by the Purdue Department of Physics and Astronomy. Findings showed the graphene sheathing protected the nanowires even while being subjected to 2.5 megawatts of energy intensity per square centimeter from a high-energy laser, which vaporizes the unwrapped wires. The unwrapped wires were damaged with an energy intensity as little as .8 megawatts per square centimeter. (The paper is available at http://pubs.acs.org/doi/abs/10.1021/acsnano.5b04628.)

“It appears the graphene coating extracts and spreads thermal energy away from the nanowires,” Das said. The graphene also helps to prevent moisture damage.

The research is a continuation of previous findings published in 2013 and detailed in this paper: http://onlinelibrary.wiley.com/doi/10.1002/adfm.201300124/full. The work is ongoing and is supported by the National Science Foundation and a National Research Council Senior Research Associateship.

by Dr. Guillaume Chansin, Senior Technology Analyst, IDTechEx

Quantum dots have been developed since the early 80’s but it is only recently that they made an appearance in consumer products such as TVs and tablet computers. IDTechEx Research has published a new market report on quantum dots titled “Quantum Dots 2016-2026: Applications, Markets, Manufacturers”, and as part of this study we have looked at their impact on the display industry. Is this the technology that will enable LCD to rival OLED?

Expanding color gamut

The key selling point for quantum dots is that they enable a much wider color gamut with minimal re-engineering of the LCD panels. They do this by modifying the backlight (and to some extent the color filters) inside the LCD stack.

A conventional LCD backlight uses ‘white LEDs’ which are really blue LEDs with a yellow phosphor. As a result, the white light that is produced has a strong blue peak and much weaker red and green components.

Quantum dots can be used as “downconverters”, the same way that phosphors convert blue wavelength to longer wavelengths. They key difference is that quantum dots have very narrow emission spectra and the wavelength can be tuned by changing the size of the dots. In other words, with quantum dots it is possible to have strong emission peaks in all three primaries: red, blue, and green.

The ideal solution would be to deposit the quantum dots directly on the LED (“on-chip”). But the current generation of materials degrade quickly at high temperature so they need to be physically separated from the chip (future generation materials may enable ‘on-chip’ thanks to high heat and moisture resistance).

Two workarounds are currently available. The first one is to place a tube filled with quantum dots between the LEDs and the light guide plate. QD Vision is the company commercializing this solution. While the tube can be fitted in large displays, it is not the best solution when it comes to mobile displays. The picture below shows an iMac retrofitted with a tube by QD Vision.

Source: IDTechEx Research.

Source: IDTechEx Research.

Back in 2013, QD Vision partnered with Sony to launch the first quantum dot LCD TV. QD Vision has now found more partners, including TCL launching a range of TVs and Philips commercializing the first quantum dot monitor this year.

The other integration option is to add the quantum dots as a film, an approach designed by Nanosys. The company has partnered with 3M to offer a diffuser sheet loaded with quantum dots. Because the diffuser sheet is part of a conventional backlight anyway, the display manufacturers do not need to change anything in the design of the backlight: the 3M solution is a direct drop-in replacement. Amazon was the first customer when it launched tablets with premium displays (the Kindle HDX).

The cadmium question

Quantum dots appear to offer a simple way to dramatically improve the performance of LCD panels. But there are some challenges to get the technology adopted.

First, the cost. A quantum dot film can add a significant cost to the display panel. Using tubes from QD Vision is probably more cost effective which is probably why several Chinese TV manufacturers are adopting this solution.

Second, consumers will have to be convinced that it will be worth paying a premium. Supporters of quantum dots say that it is currently the only way to obtain TV displays that are compliant with the Rec. 2020 standard. But while the specifications are impressive, it is worth noting that most consumers are not aware of the limitations of their existing LCD devices (whether TV, laptop, or tablet).

Third, the best quantum dots are made with Cadmium, an element which is usually banned in the European Union under the RoHS regulations. QD Vision and 3M have requested an exception to introduce cadmium in TVs because of the benefits in terms of lower energy consumption (thereby reducing carbon emissions). But some organizations, including Nanoco, are calling for the exception to not be extended. Nanoco supplies indium based quantum dots so would benefit from a complete ban on cadmium. Some are quick to retort that Indium is a potential carcinogen and might also be banned in the future.

While this debate is much needed to fully assess the risks, there is no denying it has also been damaging to the whole industry. Giving quantum dots a bad reputation is not the best way to get the technology widely accepted.

Nanoco has licensed their cadmium-free quantum dots to Dow Chemicals. But the optical performance of these quantum dots is not on par with the ones made with cadmium. The company believes that eventually they will be able to offer a similar level of performance. Meanwhile, Nanosys has also started to produce cadmium-free quantum dots and has licensed their technology to Samsung.

QLED as the next generation OLED?

While the main focus is currently on enhancing backlights for LCD panels, some are already looking beyond. Quantum dots can also be used to make emissive displays. So-called quantum dot LED (QLED) are similar to OLED with an active layer made with quantum dots.

Market forecast for quantum dot devices and components (Source: IDTechEx report “Quantum Dots 2016-2026: Applications, Markets, Manufacturers”)

Market forecast for quantum dot devices and components (Source: IDTechEx report “Quantum Dots 2016-2026: Applications, Markets, Manufacturers”)

This technology is still in very early stage but promises to offer the same benefits in terms of color gamut to OLED technology. QLED will in theory provide better colors and efficiency than OLED because of the narrower emission peaks. QLED can be considered as the next generation OLED.

Whether it is for downconversion or ultimately QLED, quantum dots have the potential to significantly disrupt the display industry. IDTechEx Research forecasts that quantum dots will enables a market of devices and components worth over $11bn by 2026, with a large chunk of the revenues in display applications. Quantum dots have already made serious inroads in the industry; don’t be surprised to find them in your next TV. For more information, read the full global analysis of the technology and application landscape in the report “Quantum Dots 2016-2026: Applications, Markets, Manufacturers” at www.IDTechEx.com/qd.