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Colourful LEDs made from a material known as perovskite could lead to LED displays which are both cheaper and easier to manufacture in future.
A hybrid form of perovskite – the same type of material which has recently been found to make highly efficient solar cells that could one day replace silicon – has been used to make low-cost, easily manufactured LEDs, potentially opening up a wide range of commercial applications in future, such as flexible colour displays.
This particular class of semiconducting perovskites have generated excitement in the solar cell field over the past several years, after Professor Henry Snaith’s group at Oxford University found them to be remarkably efficient at converting light to electricity. In just two short years, perovskite-based solar cells have reached efficiencies of nearly 20%, a level which took conventional silicon-based solar cells 20 years to reach.
Now, researchers from the University of Cambridge, University of Oxford and the Ludwig-Maximilians-Universität in Munich have demonstrated a new application for perovskite materials, using them to make high-brightness LEDs. The results are published in the journal Nature Nanotechnology.
Perovskite is a general term used to describe a group of materials that have a distinctive crystal structure of cuboid and diamond shapes. They have long been of interest for their superconducting and ferroelectric properties. But in the past several years, their efficiency at converting light into electrical energy has opened up a wide range of potential applications.
The perovskites that were used to make the LEDs are known as organometal halide perovskites, and contain a mixture of lead, carbon-based ions and halogen ions known as halides. These materials dissolve well in common solvents, and assemble to form perovskite crystals when dried, making them cheap and simple to make.
“These organometal halide perovskites are remarkable semiconductors,” said Zhi-Kuang Tan, a PhD student at the University of Cambridge’s Cavendish Laboratory and the paper’s lead author. “We have designed the diode structure to confine electrical charges into a very thin layer of the perovskite, which sets up conditions for the electron-hole capture process to produce light emission.”
The perovskite LEDs are made using a simple and scalable process in which a perovskite solution is prepared and spin-coated onto the substrate. This process does not require high temperature heating steps or a high vacuum, and is therefore cheap to manufacture in a large scale. In contrast, conventional methods for manufacturing LEDs make the cost prohibitive for many large-area display applications.
“The big surprise to the semiconductor community is to find that such simple process methods still produce very clean semiconductor properties, without the need for the complex purification procedures required for traditional semiconductors such as silicon,” said Professor Sir Richard Friend of the Cavendish Laboratory, who has led this programme in Cambridge.
“It’s remarkable that this material can be easily tuned to emit light in a variety of colours, which makes it extremely useful for colour displays, lighting and optical communication applications,” said Tan. “This technology could provide a lot of value to the ever growing flat-panel display industry.”
The team is now looking to increase the efficiency of the LEDs and to use them for diode lasers, which are used in a range of scientific, medical and industrial applications, such as materials processing and medical equipment. The first commercially-available LED based on perovskite could be available within five years.
Explore further: Scientists develop pioneering new spray-on solar cells
More information: Nature Nanotechnology, www.nature.com/nnano/journal/v… /nnano.2014.149.html
Read more at: http://phys.org/news/2014-08-material-perovskite.html#jCp
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SUBCOMMITTE EXAMINES BREAKTHROUGH NANOTECHNOLOGY OPPORTUNITIES FOR AMERICA
WASHINGTON, DC – The Subcommittee on Commerce, Manufacturing, and Trade, chaired by Rep. Lee Terry (R-NE), today held a hearing on:
“Nanotechnology: Understanding How Small Solutions Drive Big Innovation.”
“Great Things from Small Things!” … We Couldn’t Agree More!
A house window that doubles as a solar panel could be on the horizon, thanks to recent quantum-dot work by researchers at Los Alamos National Laboratory in the US in collaboration with scientists from University of Milano-Bicocca (UNIMIB) in Italy.
Their work, published earlier this year in Nature Photonics, demonstrates that superior light-emitting properties of quantum dots can be applied in solar energy by helping more efficiently harvest sunlight.
“The key accomplishment is the demonstration of large-area luminescent solar concentrators that use a new generation of specially engineered quantum dots,” said lead researcher Victor Klimov of the Center for Advanced Solar Photophysics at Los Alamos. Quantum dots are ultra-small bits of semiconductor matter that can be synthesized with nearly atomic precision via modern methods of colloidal chemistry.
A luminescent solar concentrator (LSC) is a photon-management device, representing a slab of transparent material that contains highly efficient emitters such as dye molecules or quantum dots. Sunlight absorbed in the slab is re-radiated at longer wavelengths and guided toward the slab edge equipped with a solar cell.
Sergio Brovelli, a faculty member at UNIMIB and a co-author of the paper, explained, “The LSC serves as a light-harvesting antenna which concentrates solar radiation collected from a large area onto a much smaller solar cell, and this increases its power output. LSCs are especially attractive because in addition to gains in efficiency, they can enable new interesting concepts such as photovoltaic windows that can transform house facades into large-area energy-generation units.”
Because of highly efficient, color-tunable emission and solution processability, quantum dots are attractive materials for use in inexpensive, large-area LSCs. To overcome a nagging problem of light reabsorption, the Los Alamos and UNIMIB researchers developed LSCs based on quantum dots with artificially induced large separation between emission and absorption bands, known as a large Stokes shift.
These “Stokes-shift-engineered” quantum dots represent cadmium selenide/cadmium sulfide (CdSe/CdS) structures in which light absorption is dominated by an ultra-thick outer shell of CdS, while emission occurs from the inner core of a narrower-gap CdSe.
Los Alamos researchers created a series of thick-shell (so-called “giant”) CdSe/CdS quantum dots, which were incorporated by their Italian partners into large slabs (sized in tens of centimeters across) of polymethylmethacrylate. While being large by quantum dot standards, the active particles are still tiny, only about hundred angstroms across.
Quantum dots are ultra-small bits of semiconductor matter that can be synthesized with nearly atomic precision via modern methods of colloidal chemistry.
Their emission color can be tuned by simply varying their dimensions. Color tunability is combined with high emission efficiencies approaching 100%.
These properties have recently become the basis of a new technology — quantum-dot displays — employed, for example, in the newest generation of the Kindle Fire e-reader.
In a new SPIE.TV video, Lawrence Berkeley National Lab director Paul Alivisatos demonstrates the Kindle Fire quantum-dot display.
SUBCOMMITTE EXAMINES BREAKTHROUGH NANOTECHNOLOGY OPPORTUNITIES FOR AMERICAWASHINGTON, DC – The Subcommittee on Commerce, Manufacturing, and Trade, chaired by Rep. Lee Terry (R-NE), today held a hearing on “Nanotechnology: Understanding How Small Solutions Drive Big Innovation.” Nanotechnology is science, engineering, and technology conducted at the nanoscale, which is approximately 1 to 100 nanometers (one nanometer is a billionth of a meter). This technology brings great opportunities to advance a broad range of industries, bolster our U.S. economy, and create new manufacturing jobs. Members heard from several nanotech industry leaders about the current state of nanotechnology and the direction that it is headed.
“Just as electricity, telecommunications, and the combustion engine fundamentally altered American economics in the ‘second industrial revolution,’ nanotechnology is poised to drive the next surge of economic growth across all sectors,” said Chairman Terry.
Dr. Christian Binek, Associate Professor at the University of Nebraska-Lincoln, explained the potential of nanotechnology to transform a range of industries, stating, “Virtually all of the national and global challenges can at least in part be addressed by advances in nanotechnology. Although the boundary between science and fiction is blurry, it appears reasonable to predict that the transformative power of nanotechnology can rival the industrial revolution. Nanotechnology is expected to make major contributions in fields such as; information technology, medical applications, energy, water supply with strong correlation to the energy problem, smart materials, and manufacturing. It is perhaps one of the major transformative powers of nanotechnology that many of these traditionally separated fields will merge.”
Dr. James M. Tour at the Smalley Institute for Nanoscale Science and Technology at Rice University encouraged steps to help the U.S better compete with markets abroad. “The situation has become untenable. Not only are our best and brightest international students returning to their home countries upon graduation, taking our advanced technology expertise with them, but our top professors also are moving abroad in order to keep their programs funded,” said Tour. “This is an issue for Congress to explore further, working with industry, tax experts, and universities to design an effective incentive structure that will increase industry support for research and development – especially as it relates to nanotechnology. This is a win-win for all parties.”
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Professor Milan Mrksich of Northwestern University discussed the economic opportunities of nanotechnology, and obstacles to realizing these benefits. He explained, “Nanotechnology is a broad-based field that, unlike traditional disciplines, engages the entire scientific and engineering enterprise and that promises new technologies across these fields. … Current challenges to realizing the broader economic promise of the nanotechnology industry include the development of strategies to ensure the continued investment in fundamental research, to increase the fraction of these discoveries that are translated to technology companies, to have effective regulations on nanomaterials, to efficiently process and protect intellectual property to ensure that within the global landscape, the United States remains the leader in realizing the economic benefits of the nanotechnology industry.”
James Phillips, Chairman & CEO at NanoMech, Inc., added, “It’s time for America to lead. … We must capitalize immediately on our great University system, our National Labs, and tremendous agencies like the National Science Foundation, to be sure this unique and best in class innovation ecosystem, is organized in a way that promotes nanotechnology, tech transfer and commercialization in dramatic and laser focused ways so that we capture the best ideas into patents quickly, that are easily transferred into our capitalistic economy so that our nation’s best ideas and inventions are never left stranded, but instead accelerated to market at the speed of innovation so that we build good jobs and improve the quality of life and security for our citizens faster and better than any other country on our planet.”
Chairman Terry concluded, “Nanotech is a true science race between the nations, and we should be encouraging the transition from research breakthroughs to commercial development. I believe the U.S. should excel in this area.”
** From NanoMarkets LC The new generation of wearable and flexible gadgets such as smart watches, glasses, and fitness trackers, all require batteries that are flexible and small enough to fit into these devices. This could give a big boost to the prospects for thin film and printed batteries, but it’s not yet clear which companies will benefit most. Existing thin film (TF) battery suppliers may be able to leverage their expertise, but OEMs are pursuing wearable applications and developing their own batteries, posing a threat to the TF battery suppliers.
While multiple large and influential companies are pursuing TF battery technology, two in particular seem well-positioned and motivated to go after the wearable electronics sector: LG Chemical and Apple.
LG Chemical Expanding its Offerings
LG Chemical has its eye on new battery technologies and announced in October 2013 that it had succeeded in producing batteries with different shapes. Among these are stepped batteries, a design that stacks two or more batteries on top of each other in a stepped configuration to adapt to mobile devices of various shapes, and curved batteries, which are a natural fit for curved devices. Stepped batteries may be helpful for mobile phones but are not especially desirable for wearable devices. Curved batteries could be an option but may not be flexible enough.
While LG is already manufacturing stepped and curved batteries, it has another technology in the works that seems perfectly suited for use in watch bands. The company is planning to produce cable batteries, which are flexible, waterproof, and can even be tied into a knot. This versatility makes them compatible with wearable devices, and they were in fact designed with exactly this market in mind. NanoMarkets sees this as a compelling technology that may enable growth in the wearable devices market.
The company is definitely aiming at increasing its market share in various battery technologies, including those directed at the wearables market. Given its brand name recognition and production capabilities, it could well be in a position to take business away from existing thin film battery suppliers.
Apple Eyeing Shaped Batteries
Apple is almost certainly going to be a key influencer of the wearables market, presumably through a smart watch project. The rumor mill has produced various possible concepts for an iWatch, and it’s hard to know what form such a watch will eventually take. But it will need a battery, and Apple’s patent application published in July 2013 detailing the creation of a flexible battery shape suggests Apple’s interest in producing the battery itself.
Apple’s patent, which was filed in December 2011, covers a flexible battery pack that consists of several different cells connected through a laminate layer and is designed to be able to conform to meet the needs of flexible electronic devices. The patent also allows for a battery pack where certain cells are can be removed to incorporate cooling devices, flashes, or cameras, allowing the battery to fit more snugly into a small space.
While not all of Apple’s many patents lead to products, this does point the way toward the company entering the flexible battery market. It makes sense for Apple to have a vested interest in battery technology. Perhaps Apple could license the concept for its flexible battery pack to a subcontractor, opening the door for a smaller company to benefit from growth in batteries for wearable devices.
Prospects for Thin Film Battery Suppliers
Existing TF battery manufacturers have been struggling for a long time to develop products that the market will want to buy, but there is a window of opportunity with the growth of new product segments such as wearables. Small battery companies do, however, face a real threat from OEMs and a risk that the larger companies may run them out of business.
The story is not all gloomy, though, as there are multiple avenues the smaller firms can take. They may be able to forge partnerships with OEMs by convincing them that their years of expertise producing batteries are valuable. Such collaboration could take the form of a contract agreement, acquisition, or strategic investment from these influential firms.
If wearables eventually grab the interest of consumers the way cell phones have, the potential market is huge. This is likely to be some years off, but it is wise for battery manufacturers to plan ahead. Collaborating with OEMs can be a way for smaller firms to achieve the production volumes necessary to be considered a serious contender.
Regardless of whether TF battery manufacturers manage to succeed on their own or with the support of larger players, they will only be able to do so if they can provide batteries that are compatible with the needs of wearable devices. Flexibility alone is not sufficient, and suppliers that tried and failed to conquer the RFID space will need to develop new types of products that will work well in watches and other wearables. The companies who have been in the printed battery business the longest are not necessarily in a good position to succeed in getting their products into wearable devices.
Imprint Energy looks like the TF battery firm most likely to succeed in the wearable electronics market, because its printed zinc batteries can address the need to provide long-lasting, flexible batteries that can be recharged. The solid polymer electrolyte allows Imprint’s batteries to be rechargeable, something that has been a challenge for zinc batteries and is an enabling feature for wearable devices. Disposable printed batteries really aren’t suitable here.
Imprint’s Zincpoly™ technology is also less toxic compared to lithium ion batteries, a factor that is critical in medical implants but also provides an advantage in perception of safety for wearable devices marketed to consumers. This should help Imprint market its technology.
Although Imprint’s technology is compelling for the wearables market, it is a small company without the resources to scale up to high volume manufacturing. A likely scenario is for it to follow the path of collaboration, either developing a partnership with a company that has sufficient manufacturing facilities or licensing its technology.
The Future of Batteries in Wearable Devices
The market for batteries in wearable devices is currently relatively small, but NanoMarkets forecasts significant growth in this sector, with revenue more than tripling over the next two years and increasing more dramatically through the end of the decade. This means potential opportunities for companies that can provide flexible, rechargeable batteries that can conform to whatever form factors the OEMs dream up and have reasonable power and battery life. If small companies want to get in on the action, they will need to act quickly before the OEMs start producing their own batteries custom-made to work with their specific products.
See more at: http://nanomarkets.net/market_reports/report/thin_film_and_printed_batteries_markets_2014_2021
** From NanoMarkets LC July 21st, 2014
Flexible glass seemed like a natural fit for the display industry, combining the impermeability of glass with the flexibility of plastic. In 2012 it appeared as though flexible and ultrathin glass companies were going to benefit from the explosion of touch screens in displays of all sizes. Unfortunately, the market took a different turn. Now suppliers of ultrathin and flexible glass are looking for applications beyond displays to bring in revenue in the next few years, and one of the places they are looking is in semiconductor packaging.
For those who approach flexible glass from the point of view of a display, an application where the glass is hidden between layers of silicon and other materials may not seem to make a lot of sense. As far as NanoMarkets can tell, no one really thought about semiconductor packaging as a use for flexible glass until the display market failed to emerge as an opportunity.
Nonetheless, using ultrathin glass in semiconductor packaging may actually be a very good idea, even though its optical properties and flexibility are irrelevant in this application.
The Role of Glass in Interposers
For many years the semiconductor packaging industry has been developing packages that are smaller, thinner, and lighter than what has come before. Ultrathin glass, 30 to 100 μm, may be able to further progress toward this goal.
The target application is 2.5D or 3D multi-chip or chip scale packages (CSP), where semiconductor chips are placed in close proximity or stacked on top of each other to provide a space-saving configuration. Such packages traditionally use a layer of thinned silicon as an interposer to connect chips to each other and to the underlying organic substrate. Silicon has the advantage of being a familiar material with a well-established infrastructure in the semiconductor packaging industry, but it does have some drawbacks, the major one being cost.
Glass may be preferable to silicon as an interposer because it is a less expensive material, it can be provided in thin sheets (silicon has to be ground and polished to the proper thickness) and it is thermally insulating. Silicon is a semiconductor, not an electrical insulator, which can cause problems with crosstalk between chips.
Silicon conducts heat better than glass, making the semiconductor industry a bit suspicious of the ability of glass to conduct heat sufficiently to avoid hot spots in sensitive ICs. The answer is in the through-glass vias (TGV), channels drilled through the interposer that are filled with metal (usually copper) and form electrical connections between the chip and the organic substrate. Solid filled vias act like heat pipes to provide a path for heat conduction.
The potential cost advantages of glass can best be achieved using large sheets of glass, thus allowing facilities to process more units in parallel than is possible with silicon wafers. The largest possible cost savings of using flexible glass is realized if it can be integrated into a roll-to-roll production process. Several suppliers are producing flexible glass on rolls, but the semiconductor industry is not necessarily prepared to process it.
Re-evaluating the Supply Chain
While glass may be a compelling interposer material from the point of view of glass makers, lack of infrastructure in this application is a real problem. In order for glass to be useful as an interposer, someone needs to drill vias through the glass and metallize them, and it is not yet clear who that would be. Several industries could participate in the supply chain, but there are barriers in all cases:
Semiconductor packaging houses: This industry is not used to working with glass and is not inclined to do so. It is very resistant to change and may be especially averse to implementing R2R processing. Convincing semiconductor packaging facilities to process glass will clearly be an uphill battle.
Flat-panel display manufacturers: These companies have experience with glass but have not historically had anything to do with semiconductor packaging. It may be possible to build awareness in this sector, but the flat panel display industry prefers to sell large pieces of glass.
Printed circuit board manufacturers: The PCB industry currently makes organic interposers, geared toward applications where fine pitch is not required. Glass suppliers might be able to work with the PCB industry, which is used to large panels, if they want to supply sheets of glass. It still may be difficult, however, to implement very thin glass using this approach. It also will probably be difficult to integrate TGV production into a PCB-like process flow.
Organizations that are promoting ultrathin glass interposers are attempting to address the infrastructure challenge:
Georgia Tech: The Packaging Resource Center (PRC) at Georgia Tech has been working with industry partners on glass interposers since 2010 and has moved from initial trials with 180-μm thick glass down to the thinnest products that today’s glass suppliers are producing. The PRC is working with major glass suppliers such as Corning and Schott, who are interested in flexible glass interposers.
The PRC has been working on transferring the technology from prototype to low volume, and perhaps eventually high volume, commercial production. It has made some real progress in developing the technology and moving prototyping from labs into industry, but admits that the greatest challenge in moving forward is lack of infrastructure to support the transition.
Triton: Triton Micro Technologies, a subsidiary of nMode solutions that is partially funded by Asahi Glass Company, is providing some missing segments in the supply chain. Triton has developed a production process to create through glass vias (TGVs) that is sufficient for today’s 2.5D applications and it is making interposers for MEMS, RF, and optics at its manufacturing facility in Carlsbad, CA. According to Triton, the major advantage it provides over silicon is the ability to produce solid filled, hermetic TGVs.
Existing commercial products use glass interposers from Triton, but this is much thicker glass, typically 0.3 mm or greater. The glass is cut into wafers, matching the form factor of silicon but not requiring backgrinding. This provides the convenience of a process that fits easily into existing manufacturing lines but doesn’t take advantage of glass’ potential to provide thinner interposers at much lower cost than silicon. Triton can make large panels of 0.1-mm glass with TGVs, but customers do not know how to handle it and may not be inclined to learn.
NanoMarkets understands the potential advantage thin glass would have as an interposer, but is not especially optimistic about its future, especially in the near term. It seems very unlikely that flexible glass will be able to generate large revenues in this space, even if penetration rates get large. Each product uses a very small amount of glass compared to what would be needed for even a smart phone display.
The semiconductor packaging industry may be an even more difficult environment for introducing new processes than the display industry, and we know flexible glass has had challenges there. Still, we feel this sector is worth keeping an eye on to see if glass has an opportunity to succeed where silicon has not.
See More: http://nanomarkets.net/market_reports/report/flexible-glass-markets-2014-and-beyond
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