Nanoparticle ink could print solar cells like newspaper

28 August 2009

Country: United States

Nanoparticle inks could be used to print solar cells like newspaper, or painted onto the side of buildings or rooftops to produce electricity.

Manufacturing solar cells using gas-phase deposition in a vacuum chamber requiring high temperatures is relatively expensive. However, according to Professor Brian Korgel, University of Texas, Austin, and co-founder of Innovalight, it may be possible to reduce these costs by an amazing 90% - making the price of solar energy more competitive with other technologies.

Chemical engineering Professor Brian Korgel tests one of his printed solar cells. Source: University of Texas.

His team has been working on a solution of nanomaterials using copper indium gallium selenide (CIGS) which is not only cheaper than silicon but you also use less of it when manufacturing solar cells. The light-absorbing nanomaterials are 10,000 times thinner than a strand of hair, because their microscopic size allows for new physical properties that can help enable higher-efficiency devices.

Researchers apply the nanoparticle "inks" as a spray on the solar cells. Source: University of Texas.

His team has only developed a solar cell prototype at 1% efficiency, but in order to make the product commercially viable, they need to achieve 10% efficiencies, which Korgel believes could be possible within the next 3-5 years.

Not only could the inks, which are semi-transparent be printed on a roll-to-roll printing process on a plastic substrate or stainless steel, they could also be used on windows that double up as solar cells. Korgel says the prospect of being able to paint the "inks" onto a rooftop or building is not far-fetched - "you would have to paint the light-absorbing material and a few other layers as well," he concludes.

They recently demonstrated proof-of-concept in a recent issue of "Journal of the American Chemical Society". The work has attracted the interest of industrial partners.

Innovalight recently installed a system to inkjet print silicon-ink, which they claim can halve the number of costly manufacturing processes required to produce highly efficient solar cells.

Whilst researchers at the UCLA Henry Samueli School of Engineering and Applied Science have developed a low-cost solution processing method for CIGS-based solar cells . They used hydrazine as the solvent to dissolve copper sulfide and indium selenide in order to form the constituents for the copper-indium-diselenide material. Their material, which is simply dissolved into a liquid, can be easily painted or coated evenly onto a surface and baked. The solar cells achieved over 9% efficiency in the lab.

Top image: At the core of Korgel's research are the nanoparticle "inks" (as shown here) which are the sunlight-absorbing materials of his solar cells. Source: University of Texas.

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Graphene-stabilized copper nanoparticles as an air-stable substitute for silver and gold in low-cost ink-jet printable electronics

CLICK pic to ENLARGE

Figure 4. Printed copper patterns. (a) Line patterns for electrical
conductivity measurements. The inset shows a homogeneous and
crack-free print surface. (b) Manually cracked pattern for
investigation of the film thickness after five overprints, revealing a
print thickness of 500 nm per print cycle. The magnification inset of
the fracture surface shows the inner structure of the composite film.
(c) Graph showing the decrease of resistance with larger line width
of the pattern (error bars obtained from five samples at each line
width). The mean electrical conductivity was 1.56 ± 0.48 S cm−1.
(d) Light-emitting diodes directly glued onto printed copper lines.
Norman A Luechinger 2008 Nanotechnology doi: 10.1088/0957-4484/19/44/445201

	PDF (611 KB) | References

Norman A Luechinger, Evagelos K Athanassiou and Wendelin J Stark¹
Institute for Chemical and Bioengineering, Department of Chemistry and Applied Biosciences, ETH Zurich, CH-8093 Zurich, Switzerland
¹ Author to whom any correspondence should be addressed
E-mail: wendelin.stark@chem.ethz.ch

Abstract. Metallic copper nanoparticles were synthesized by a bottom-up approach, and in situ coated with protective shells of graphene in order to get a metal nanopowder of high air stability and chemical inertness. Using an amphiphilic surfactant, a water-based copper nanocolloid could be prepared and successfully printed onto a polymer substrate by conventional ink-jet printing using household printers. The dried printed patterns exhibited strong metallic gloss and an electrical conductivity of >1 S cm^-1 without the need for a sintering or densification step. This conductivity currently limits use in electronics to low current application or shielding and decorative effects. The high stability of graphene-coated copper nanoparticles makes them economically a most attractive alternative to silver or gold nanocolloids, and will strongly facilitate the industrial use of metal nanocolloids in consumer goods.

Print publication: Issue 44 (5 November 2008)
Received 11 July 2008, in final form 19 August 2008
Published 26 September 2008

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Nano-inks could advance printed electronics

R. Colin Johnson
EE Times
(07/28/2008 10:48 AM EDT)

PORTLAND, Ore. — Nano-inks for aerosol printing of electronics circuitry are being jointly developed by Applied Nanotech Inc. and Optomec for its M3D aerosol jet printer.

Optomec's jet printer transfers metallic, semiconducting and insulating inks onto any shaped substrate. Aerosol Jet printing like ink-jet printing can reproduce electronic circuits on inexpensive flexible polymer films.

Optomec's printer is designed for rapid prototyping of new devices and short production runs, but printable electronics is also poised to debut in consumer electronics devices later this year, according to IDTechEx Ltd. (Cambridge, Mass.) Printed electronics applications include patterning circuit boards, solar panels, on-battery testers, RFID tags, interconnection planes and other flexible electronics.

Most ink-jet printing is currently done with silver inks, which are expensive compared to copper nano-inks announced by Applied Nanotech (Austin, Texas) and Optomec (Albuquerque, N.M.). Current copper inks copper flakes over 250 nanometers in size, requiring 424-degree F annealing. Applied Nanotech said its copper nanoparticles 10 to 20 nanometers and can be deposited at annealing temperatures below 212 degrees F.

The Optomec printer's minimum feature size of 10 microns prompted it to partner with Applied Nanotech to optimize its ultra-small-particle nano-inks for the M3D, which uses a finer nozzle configuration than ink-jet printers. Optomec also employed an aerodynamic flow guidance deposition head which can be focused to a virtual nozzle size of 10 microns. Since the deposition head is over 5 millimeters away from the substrate, it allows 3-D surfaces to be "painted" with electronic circuitry.

Applied Nanotech said it is also developing other nano-inks based on other nanoparticles formulations, including carbon nanotubes.

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Printable Thin-Film Transistor for Flexible Electronics

United States Patent Application	20080173865
Kind Code	A1
Fink; Richard Lee ; et al.	July 24, 2008

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Abstract

Fabrication of thin-film transistor devices on polymer substrate films that is low-temperature and fully compatible with polymer substrate materials. The process produces micron-sized gate length structures that can be fabricated using inkjet and other standard printing techniques. The process is based on microcrack technology developed for surface conduction emitter configurations for field emission devices.

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Inventors:	Fink; Richard Lee; (Austin, TX) ; Yaniv; Zvi; (Austin, TX)
Assignee Name and Adress:	NANO-PROPRIETARY, INC. Austin TX Claims 1. A thin film transistor (TFT) comprising:a substrate;a source electrode on the substrate;a drain electrode on the substrate positioned a distance from the source electrode;a layer of metal oxide deposited on the substrate between the source and drain electrodes, wherein the layer of metal oxide is reduced to metal to form a microcrack in the layer between the source and drain electrodes, wherein the microcrack separates a first portion of the metal layer contacting the source electrode from a second portion of the metal layer contacting the drain electrode;an active semiconductor material deposited so that it bridges the microcrack, contacting both the first and second portions of the metal layer;a gate dielectric material deposited over the active semiconductor material; anda gate electrode deposited on the gate dielectric material and not contacting the metal layer or the active semiconductor material. 9. A method of manufacturing a TFT comprising:inkjet printing conductive ink on a substrate to form source and drain electrodes spaced apart from each other;inkjet printing a PdO layer on the substrate between the source and drain electrodes;reducing the PdO layer to Pd metal resulting in formation of a microcrack in the Pd metal layer;inkjet printing an active semiconductor on the reduced PdO layer across the microcrack;inkjet printing a gate dielectric over the active semiconductor; andinkjet printing a gate electrode over the gate dielectric.

Advantages of this approach are:

[0041]1. Low cost: All-printing technologies are used to form feedlines and TFT components. Inkjet printing and other printing approaches may he used. Printing is an additive approach and not subtractive, thus in general, the materials cost will be less. In addition, the capital investment for printing equipment is much lower than CVD or vapor deposition equipment needed for a-Si TFT technology or high-performance pentacene transistors.

[0042]2. Low temperature; The fabrication processes are below 200.degree. C.

[0043]3. Compatible with flexible substrates: The fabrication processes are completely compatible with PEN substrates.

[0044]4. Scalable to large area: Ink-jet printers are used now to print billboard signage. 100'' diagonal will be no problem. The fact that Canon, is using this microcrack approach for their SED 36'' diagonal (and larger) displays also demonstrates that arrays of submicron channel TFTs can be fabricated over large areas reliably.

[0045]5. Performance specifications for emissive technologies: The driving currents from this TFT structure are sufficient to drive OLEDs.

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Nanosolar Printing Video

Nanosolar's proprietary nanoparticle ink.

Here comes the sun

Posted: June 23, 2008, 9:15 PM by Chris Boutet

Nanosolar’s breakthrough technology is 10 times more powerful than a nuclear reactor and cheaper, too

By Lawrence Solomon

Go to YouTube and you can see a corporate video of a printing press running at 100 feet per minute, applying a nanoparticle ink to foil and producing solar cells. This machine is owned by Nanosolar Inc., which in turn is partly owned by Sergey Brin and Larry Page, the founders of Google. This one printing machine, Nanosolar claims, can produce solar cells with a capacity of 1,000 MW per year, the equivalent of a nuclear reactat Indian Point outside Manhattan or two nuclear reactors at Pickering outside Toronto.

Unlike nuclear reactors, which take a decade to build and billions of dollars in capital costs before delivering a single kilowatt-hour to a home or business, Nanosolar’s breakthrough technology can help meet society’s power needs soon after its ink has dried, and the press’s capital costs amount to a mere $1.65-million. Put another way, we can wait 10 years to get nuclear power up and running. Or, by relying on a single Nanosolar press, we can have the solar equivalent of a major nuclear plant in one year, and the equivalent of 10 major plants in a decade. Soon, says Nanosolar, its printing presses will be operating much faster — perhaps 20 times faster. Should this prove feasible, a single Nanosolar press would pump out in a single decade the equivalent of 200 nuclear plants — far more than now exist in all of North America.

To add to the slam-dunk superiority of Nanosolar-type technology over nuclear, solar cells produce power when we especially need it — when people are awake and industries are humming. During the low-value off-peak hours when power is in great surplus, the solar cells sleep, too. Nuclear reactors, by contrast, can’t ratchet down or turn off when their output isn’t needed. Off-peak nuclear power, in fact, is sometimes produced at a loss because its operating costs exceeds the pittance earned at, say, 3 a.m.

To get bang for the buck, and obtain the power that a growing economy needs, nuclear and solar are as different as night and day. Nuclear power, a half-century after the launch of the first generation of nuclear reactors, remains an immature technology, each successive generation proving to be not only unreliable but also subject to ever-higher costs. Solar technology, in contrast, becomes ever more reliable and ever less costly, and is only immature in the same way that computer technology is immature — there is no end in sight yet to how far and fast it can go.

Nanosolar, founded in 2002 by two Stanford PhD candidates applying Silicon Valley smarts, is a case in point. By the end of 2003, it had obtained 60 patents, By 2004, it had developed its printing method. By 2006, it had published its results in a peer-reviewed journal and, within months, raised $100-million. By the end of 2007 it had made its first commercial shipment. Now Nanosolar can’t keep up with the demand — its factory’s output for the next 12-months is pre-sold.

Nanosolar’s solar panels could go on rooftops but the company recommends against this — at least until building codes become flexible enough to accommodate panels without the need to battle municipal bureaucracies. Besides, it says, it is developing a residential product sure to wow the homeowner.

In the meantime, it touts small municipal solar power plants that can be up and running in one year on the outskirts of cities and towns, where land is readily available. Each would be between 2 MW and 10 MW in size — enough to power 1,000 to 5,000 homes. Put one of these in several hundred cities and a nuclear plant’s worth of power would be delivered, locally and in a decentralized manner, and without the expensive and unsightly transmission towers that accompany large nuclear plants.

As impressive as Nanosolar is, here’s something more impressive still: This company is but one of several with solar breakthroughs that stand to revolutionize the energy world. Some of the competing solar technologies are designed for large-scale applications, some small. In this dynamic new energy marketplace, some will prosper and, doubtless, some will fail, just as many of the computer pioneers in the 1970s and 1980s failed for one reason or another. But large or small, well capitalized or not, the solar technologies are working more impressively than anyone could have dreamed a decade ago and seem certain to overtake nuclear as a provider of additional power to our electricity systems. If the projections from Nanosolar and others prove accurate, in fact, they will become the most economic power source of all, besting even coal.

Clean, limitless power is now within grasp, courtesy of those who have reached for the sun.

Financial Post
LawrenceSolomon@nextcity.com

Lawrence Solomon is executive director of Energy Probe and author of The Deniers. This is the first in a series on renewable energy.

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Nano-Proprietary, Inc. and NanoReady Ltd. Announce Strategic Alliance to Commercialize Metallic Nanoparticles

Marketwire
May 15, 2008: 09:05 AM EST

Nano-Proprietary, Inc. (OTCBB: NNPP), through its subsidiary, Applied Nanotech, Inc. (ANI), and NanoReady Ltd. of Israel announced a strategic alliance for the manufacturing in volume metallic nanoparticles using NanoReady's wet chemistry process.

The initial focus of the strategic alliance will be volume production of copper nanoparticles to be utilized on a worldwide exclusive basis by ANI and its partner in Japan (a leading industrial chemical products company, see the press release of October 1, 2007) for producing inkjettable copper inks for the flexible electronics, solar cell, digital printed circuit board (PCB) and many other industries.

The current agreement with NanoReady is highly important due to ANI's fast progress in developing inkjettable copper inks. Based on this progress ANI and its partner in Japan decided that it would be important to secure volume production of copper nanoparticles and, in the future, other metallic nanoparticles for their metallic ink products.

"We are very pleased to cooperate with NanoReady and develop our products based on their proprietary wet chemistry process that is inducible to high volume production of copper nanoparticles required for our ink products," said Dr. Zvi Yaniv, president and CEO of ANI.

Ronen Frish, NanoReady's CEO, adds: "The cooperation of our two companies opens a broad range of new opportunities within the ink industry and will lead to opportunities in additional industries."

ABOUT NANO-PROPRIETARY, INC.

Nano-Proprietary, Inc. is a holding company consisting of two wholly owned operating subsidiaries. Applied Nanotech, Inc. is a premier research and commercialization organization dedicated to developing applications for nanotechnology with an extremely strong position in the fields of electron emission applications from carbon film/nanotubes, sensors, functionalized nanomaterials, and nanoelectronics. Electronic Billboard Technology, Inc. (EBT) possesses technology related to electronic digitized sign technology. The Companies have over 250 patents or patents pending. Nano-Proprietary's business model is to license its technology to partners that will manufacture and distribute products using the technology. Nano-Proprietary's website is www.nano-proprietary.com.

COMPANY CONTACT
Doug Baker
Chief Financial Officer
Nano-Proprietary, Inc.
248.391.0612
Email Contact
MEDIA CONTACT
William J. Spina
781.378.2000
Email Contact

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NanoReady Collaborative, Fast-track Improvement of Products

NanoReady is dedicated to enhancing specific characteristics of a selected element while maintaining its physical dimensions, thus enabling manufacturers to improve products and save process time and costs.

NanoReady Service is designed for manufacturers and product developers who have not yet explored the capabilities of Nanotechnology and wish to improve their products, as well as those who have nanotechnology know-how, and wish to further improve the characteristics of their products. A Nanotechnology project with NanoReady scientist will commonly be completed in the time range of 2-6 months.

Business Model

We have established a proven, effective working process for implementing a nanotechnology project with NanoReady’s scientists and industrial production experts:

1. NanoReady works with you to discuss which critical elements of your product may be improved with nanoparticle additives.
2. Together the expected material or product improvement will be defined and technical specifications for the given element/materials agreed.
3. NanoReady defines the detailed project roadmap.
4. NanoReady produces the enhanced element/materials prototype
5. Joint performance testing at your production site (stress or other tests, as appropriate)
6. If all tests are successfully performed, NanoReady works with you to set logistics for the implementation process.
   

Typically, the above process can be completed in 2- 6 months, enabling a fast time to market.

NanoReady Service can be implemented several times, including the exploration of further improvements to products that have already gone through the NanoReady Service process, enabling the improvement of additional parameters or changes to the physical dimensions without compromising performance.

Contact us to learn more about how NanoReady Service can improve your products.

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Innovalight's Silicon Ink

May 14, 2008

by Joe Kwiatkowski, Physicist, Imperial College London

London, UK [RenewableEnergyWorld.com]

The last quarter of 2007 was an exciting time for the Silicon Valley start-up Innovalight: first a successful finance round that drew US $28 million of new capital, then the accolade of being amongst Red Herring's top one hundred innovators. Why the interest in Innovalight? Because of its remarkable claim to be able to print thin-film silicon solar cells.

Printing is generally a low-cost and high throughput process, in stark contrast to conventional methods used to produce amorphous and crystalline silicon solar cells. As such, Innovalight claims it will be able to substantially reduce the cost of photovoltaics. In a recent interview, CEO Conrad Burke predicted cells may eventually be sold for US $1 per watt — a figure perhaps determined less by technological considerations and more by similar claims made by his neighbors like Nanosolar.

Although details remain tightly guarded secrets, the essential element of Innovalight's process is an ink made of silicon nanocrystals. These nanoparticles can be made in a variety of ways, for example by assembling a group of molecules that contain silicon and then burning off everything except the silicon.

A patent filed in 2005 suggests that Innovalight is using a "radiofrequency plasma" to make its nanoparticles. By blasting silicon rich molecules with an electromagnetic field (at a radio frequency) it is possible to generate a gas in which some of the molecules have lost an electrical charge. Whilst charged, the molecules are extremely reactive and, with a bit of careful chemistry, can be coerced into forming nanoparticles.

By suspending these nanoparticles in a solvent to make an ink, Innovalight can then print silicon films. However, as printed, the nanoparticles are not interconnected and so the film has a high electrical resistance. To lower the resistance, the nanoparticles have to be joined by heating them until their edges are melted, at which point neighboring particles can fuse. The melting point of bulk silicon is over 1400º C and the cost of heating is a substantial cost in the production of crystalline silicon solar cells. However, a fortunate advantage of using smaller particles is that they have lower melting temperatures. Purposefully vague in their descriptions, Innovalight says only that it uses temperatures between 300 and 900º C, (possibly at high pressure and for times that could be anywhere between 5 minutes and 10 hours). Whatever the exact details, the company evidently hopes that a low-temperature printing process could offer substantial savings over conventional silicon solar cells.

It is still unclear what efficiencies Innovalight will achieve. Presumably, because it is working with thin-film solar cells, its silicon is substantially amorphous and would therefore have stabilized efficiencies of about 10%. Whatever the efficiency, and despite the difficulties that are inevitable in developing a new technology, an advantage of Innovalight's manufacturing process is that there is a wonderful number of variables that can be adjusted to get the most out of the cells. For example, nanoparticles can be grown in a variety of shapes and sizes or different nanoparticles can be mixed to determine the exact properties of the printed cell. Or, by adding germanium and tin nanoparticles to the ink, the light absorption properties can be tuned; by printing successive layers with different absorption properties, tandem solar cells could be built that would allow higher efficiencies to be reached.

Though it is probable that Innovalight will have to compromise on cell efficiency in order maintain low costs, it has come up with a phenomenon that might just help make up for its losses. According to a recent paper published in collaboration with the National Renewable Energy Laboratory (NREL), "multiple exciton generation" has been measured in Innovalight's silicon nanoparticles. What this means is that the nanoparticles might be able to produce more electrical charges than would normally be expected from a given amount of sunlight. Without this effect, the highest efficiency that a standard solar cell could ever achieve is 31%; anything else is thermodynamically impossible. However, with multiple exciton generation, the thermodynamic limit is boosted to 44%. If Innovalight could take advantage of this phenomenon it might be able to match, or even exceed, the efficiencies of conventional silicon technologies.

With its new funds Innovalight plans to construct a 3000 square meter manufacturing facility in California, and to triple its workforce over the next year. Although there is no official date on the company's website for the start of production, 2009 has been suggested elsewhere. Until then, all we can hope for from Innovalight's printers are more announcements of funds and awards.

Joe Kwiatkowski is a physicist at Imperial College London, where he works on organic photovoltaics. His current interest is the development of computational methods that can aid the design and optimization of new photovoltaic materials.

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DuPont and Dainippon Alliance to Focus on Reducing OLEDs Production Costs

WILMINGTON, Del. and KYOTO, Japan, May 7 /PRNewswire-FirstCall/ -- DuPont and Dainippon Screen Manufacturing Co., Ltd., today announced their intention to form a strategic alliance to develop integrated manufacturing equipment for printed organic light emitting diode (OLED) displays. The companies also have signed an agreement relating to their intention to bring together the elements needed -- materials, technology and equipment -- to mass produce OLED displays, delivering higher performance at a lower cost.

OLEDs are displays in which pixels are created using thin films made of emissive organic materials. Compared with liquid crystal displays (LCDs), OLEDs can have much higher contrast ratios, lower power consumption (because pixels draw power only when they are in use), faster response time, and eliminate the need for the backlight and color filter. Small-size active matrix OLED displays have recently become available from several manufacturers, but the current high-cost of manufacturing limits market adoption, and constrains OLED manufacturing for large size displays.

"The flat panel display market is about $100 billion annually and growing. DuPont is applying its science to make possible more vivid displays that are lower cost than current LCD displays," said David B. Miller, group vice president, DuPont Electronic & Communication Technologies. "We are excited to combine our strengths with Dainippon Screen's unique printing technology to bring to market the core technology that will enable improved high definition televisions and other flat panel displays."

The companies are developing integrated coating and printing equipment for the fabrication of OLED displays from solution, an approach which is unique in the industry and can significantly reduce manufacturing costs for OLED displays. DuPont brings to the alliance its distinctive small molecule-based OLED solution materials and proprietary process technology from which excellent performance has been obtained in testing. Dainippon Screen has developed a unique printing technology, called nozzle printing, in which the OLED materials can be printed accurately at very high speed. The goal of the alliance is to develop integrated OLED printing and coating equipment that will significantly reduce the production costs of flat panel displays, with the aim of extending OLED technology to large size displays and making them cost-competitive with LCDs.

The companies have been working together over the past three years to jointly develop nozzle printers as an efficient method for printing OLED displays from solution. The first production scale printer is currently being constructed.

"We were interested in extending our deep LCD equipment experience into the OLED marketplace and we felt that DuPont had developed a much needed, viable approach to OLED materials and technology that could expedite the commercialization of cost-effective OLED manufacturing," said Yoshinari Yaoi, corporate senior executive officer and president, FPD Equipment Company, Dainippon Screen. "We believe that this alliance could be the key for manufacturers to be able to produce affordable, high-quality larger sized OLEDs using our unique nozzle printer technology."

Dainippon Screen, established in 1943, is a leading supplier of flat panel display and semiconductor equipment. Screen is currently involved in manufacturing production equipment in a variety of fields, including FPDs, semiconductors, printed circuit boards, and printing and prepress equipment such as thermal CtP recorders and on-demand printing systems. For more information, please visit: http://www.screen.co.jp/.[English site:http://www.screen.co.jp/index.html]

DuPont is a science-based products and services company. Founded in 1802, DuPont puts science to work by creating sustainable solutions essential to a better, safer, healthier life for people everywhere. Operating in more than 70 countries, DuPont offers a wide range of innovative products and services for markets including agriculture and food; building and construction; communications; and transportation. For more information, please visit: http://www.dupont.com/.

Photo: OLEDs With DuPont and Dainippon Technology -- http://www2.dupont.com/Media_Center/en_US/assets/mmg/images/DuPont_OLED_Display.jpg

Caption: 4.3" diagonal full-color OLED made with DuPont materials and Dainippon equipment

DuPont

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