The Future of Photovoltaics Manufacturing in the United States: Summary of Two Symposia (2011)

Panel V


Next Generation:
The Flex Display Opportunity

Moderator:
William Harris
Science Foundation Arizona

Mr. Harris introduced the panel, praising as he did so the “sense of urgency everyone has about this issue.” He expressed satisfaction that “everyone here claims to be the solar city.”

NEW AND SYNERGISTIC OPPORTUNITIES IN FLEXIBLE AND PRINTED ELECTRONICS

Mark Hartney
FlexTech Alliance

Dr. Hartney said he would discuss a new kind of solar technology that brings its own new capabilities and challenges—that of flexible and printable electronics—of which photovoltaics is a component. The FlexTech Alliance was formerly the U.S. Display Consortium, initiated about 15 years ago to support R&D. It structure was much like that of SEMATECH, except that it focused on the then-nascent flat-panel display industry. The consortium was supported by DARPA, and Mr. Hartney was the DARPA program manager charged with the mission of building a supply capability in flat-panel displays in the United States. While it was primarily an R&D consortium, it focused on precompetitive aspects of the supply chain. The member companies could add their own innovations, but worked from a common ground in which they shared many tools and materials. The program brought together companies that could work together and were willing to cost-share more than 60 percent of the R&D.

For the past five years, the Alliance has been funded by the Army Research Laboratory, primarily because of the Army’s keen interested in flexible displays

for their own particular needs and mission requirements. Since that time the Alliance had broadened its mission area to include other kinds of flexible electronics.

Rugged, Low-Weight, Flexible, Deformable

One trend in electronic systems, Dr. Hartney said, is that they are becoming larger; they are no longer just micro- or nanosystems. They might include, for example, six 45-inch diagonal televisions, or an eight-foot display on a single sheet of glass. They must meet many performance requirements, such as a demand for displays that are rugged, low-weight, flexible, and deformable. Some of these flexible electronic systems are arranged on ultrathin steel foil; other types of flexible electronics contain millions of transistors on a glass surface to control display pixels, or transistors on a plastic transparent substrate.

Flexible and printed electronics represented “More than Moore,” he said. Moore’s Law in silicon electronics describes the drive toward smaller features, higher density, more complexity, and higher costs. Printed electronics, by contrast, strives for sufficient functionality at lower cost. For example, printed and flexible electronics might use thousands of transistors, where silicon and glass structures use billions. Feature sizes are typically in the tens of microns as opposed to the tens of nanometers. A fab might cost from less than $5 million to $100 million, as opposed to $2 billion or $3 billion.

The Convergence of Two Worlds

Flexible and printed electronics represent the convergence of two worlds—microelectronics and graphics printing—which brings many advantages. They use familiar printing methods, he said, such as injection and gravure printing. They allow development of new products with a low cost of entry. They produce a product that is printed on graphics equipment but serves as a functional electronic device. This convergence is possible because both worlds have changed rapidly. The graphics printing business has moved toward finer and finer feature sizes, while microelectronics materials development has led toward new nanomaterial inks, plastic substrates, and organic semiconductors. “These open new possibilities,” Dr. Hartney said, “in flexible displays, flexible solar cells, and electronic newspapers you can fold in your hand.”

Flexible and printed electronics have moved through three generations. The first had passive components, such as capacitors, resistors, conductors, inductors, and RFID (radio-frequency identification) antennas. These were printed on circuit boards with metal ink. The second generation, now being developed, has active printed components. It will make use of thin film transistors for e-paper and e-books, thin-film solar cells, and microbatteries. This is likely to be followed by a third generation of completely printed active devices. Printing technologies will be used to actually build memory: complete RFID circuits, rather than those

requiring a chip to be attached later; color displays with TFT-driven light-emitting diodes; and SRAMs and CPUs. “We see flexible solar as a very important member of this family of printed electronics,” he said.

Dr. Hartney outlined some of the global market opportunities anticipated for this sector over the period 2007 to 2017. The first and most prominent will be photovoltaics. Another important segment will be electrophoretics, he said, the kind of display that powers the Amazon Kindle and other book reading devices. This display is actually flexible, but it is put into a rigid package because it is what people are used to. It could easily be decoupled from the glass substrate, rolled or folded into a smaller package, and slipped into a pocket. Another important application is organic light-emitting diode (OLED) technology, which will be important not only for displays, he said, but for high-efficiency lighting.

In today’s PV market, he said, crystalline silicon predominates, with more than 90 percent of PV shipments being silicon wafer-based material. Thin-film technologies have the highest growth rate, rising from 50 MW in 2007 to a predicted 4.5 GW by 2012. Thin film has the advantage of leveraging LCD production and its $120 billion in sunk costs, and is being used experimentally on flexible substrates. The third generation of PV products is still in the R&D and pilot stages, with some scale-up work on organic, nanostructured materials, CIGS (copper indium gallium diselenide), and other technologies that can take advantage of flexible substrate properties.

Toward Roll-to-Roll Processing

The Alliance does not focus so much on particular technologies as on the manufacturing approach, he said. Virtually all integrated circuit and display manufacturing uses discrete substrates, and these glass substrates are increasingly large, requiring batch processes with multiple steps and expensive thermal and vacuum cycling. A newer approach is to use roll-to-roll processing, which offers the opportunity for continuous flow. This technique can be modularized for different unit steps or integrated into a complete line. It enables new markets, such as building integrated photovoltaics (BIPV), which are light-weight solar materials that do not require the reinforcement of roofing before installation. He said that BIPV can even be attached to a roof with Velcro and then removed to another site.

Dr. Hartney described other roll-to-roll techniques of high potential. One, being developed by a collaboration between Hewlett Packard and Power Film in Iowa, makes use of amorphous silicon thin film on a Kapton²⁴ substrate. The same kind of substrate can be used to emboss and print the substrate of a flexible display. Another technique uses organic flexible printed materials developed by

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²⁴Kapton is the brand name of a temperature-stable polyimide film developed by Dupont which is well suited to flexible electronics.

Konarka.²⁵ These films have long lifetimes in the field, which is “probably more important than making the active layer a few percent more efficient.”

Flexible electronics also have an impact in major fields of R&D:

• Health care: New techniques in the form of smart bandages (sensors that detect thermal or bioactivity and release therapeutic agent); real-time monitoring (to sense infection, release drugs, or signal the need for intervention); and neuroimaging (assisting in precise surgery by monitoring brain activity, providing a template for the surgeon to follow, and providing greater biocompatibility).

• Agricultural and civil infrastructures: Here, flexible electronics can be used for large-area sensor networks to monitor roadways, fields, groves, water supplies, and other places. For crash barriers, OLEDs can capture sunlight during the day and cause a crash barrier to glow at night; they can also incorporate a sensor and communication system: If someone goes through a barrier, it automatically reports an accident.

• Defense and emergency responders: Flexible electronics can be rugged enough to wrap around a soldier’s uniform or used as an electronic surface on skin of airplanes. Some fighter planes must be x-rayed after every mission to ensure that its carbon fiber material is still robust, a time-consuming process; much more efficient would be an integrated sensing grid that would instantly indicate whether the skin has to be replaced. Flexible skins may help outfit the “soldier of the future,” with active camouflage, threat detection, and earth monitoring abilities; integrated solar energy sources; and these technologies could serve a dual use for similar requirements needed for first responders.

In summary, Dr. Hartney said, photovoltaics presents an enormous economic opportunity. In technologies from crystalline silicon to large-area thin film, new techniques can draw from the existing and mature semiconductor and display industries. As the industry moves into flexible and printed electronics, the level of maturity is lower. Companies, universities, and government laboratories are working to move these electronics technologies closer to maturity, a challenge that can be met only through the synergies of collaboration.

He closed with four policy recommendations, including the need for (1) sustained federal and state R&D, (2) common infrastructure development, (3) early prototyping of mission needs to drive learning cycles, and (4) innovative manufacturing support. “Getting industry to buy into collaboration is essential,” he concluded. “Many of the people we’ve talked to believe they need to do it all on their own. They haven’t recognized the value in collaboration, even with people who are competitors.”

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²⁵Konarka Technologies of Lowell, Massachusetts, makes light-weight, flexible PV that can be printed as film or coated onto surface.

ADVANCING TECHNOLOGY THROUGH
MEASUREMENT SCIENCE AT NIST

Eric K. Lin
National Institute of Standards and Technology

Dr. Lin said that he would review how the diversity of approaches in federal laboratories helps advance new technologies, and photovoltaics in particular. NIST’s own approach is primarily economic, since it is located in the Department of Commerce, so that its mission is focused on economic growth, and more specifically on innovation, measurements, and standards. These activities have obvious relevance to photovoltaics.

NIST was founded by Congress at the beginning of the industrial revolution in 1901, when the nation had many difficulties supporting its burgeoning new industries. For example, there were eight different “authoritative” values for the gallon. A new electrical industry had not yet developed its own standards, so American instruments were sent abroad for calibration—an obvious national security issue. At the time of the gold rush, a miner and a buyer had to be able to agree on what a kilogram or pound of gold would be. “They needed a neutral objective partner they trusted to be correct.”

Promoting Competitiveness at NIST

Today, Dr. Lin said, the NIST mission is to promote innovation and competitiveness in many ways that are based on science. This is done by advancing measurement science, standards, and technology in ways that enhance economic security and improve the quality of life. The main strength of the NIST campus is that it is globally recognized as a center of scientific talent.

NIST, at a glance, consists of 2,800 employees, 2,600 associates and facilities users, and 1,600 field staff in partner organizations. More than half of them have Ph.D.s, and about 400 serve on 1,000 national and international standards committees representing U.S. interests. Major programs at NIST laboratories include the Baldridge National Quality Program, Manufacturing Extension Partnership, and Technology Innovation Program (formerly the Advanced Technology Program).

The NIST laboratories function at the “professional level of science,” he said, and the level of experience and quality of NIST science make it “a national resource of great importance.” The labs provide the innovation infrastructure for much of the nation’s scientific activity. “Basically,” he said, “we’re building the ‘roads and bridges’ of research that industrial and scientific communities need to develop and commercialize new technologies.” These roads and bridges take different forms:

• Basic science and groundbreaking research.

• Performance measures for accurate technology comparisons.

• Standards to assure fairness in trade.

• Public-private partnerships to accelerate technology.

“When NIST engages with industry to facilitate innovation,” said Dr. Lin, “we really take seriously our role as a neutral, objective partner with very high standards based on fundamental science.” He gave his view of NIST’s role in technology development. It begins with promoting discovery and proof of principle, which relies on the principal investigator and peer-reviewed journal articles. A second level promotes the kinds of growth stimulated by the semiconductor industry via SEMATECH, the Flex-Tech Alliance, and other industrial organizations. With growth comes the need for standardization, transition to larger scale manufacturing, and finally a mature industry that focuses on efficiency and an integrated network of stakeholders.

Avoiding Silos, Addressing Broader Needs

At each level, he said, NIST has a role to play. For example at the discovery or proof of principle level, NIST has its world-class measurements and science, many high-impact publications, and input from National Academies members and Nobel Laureates. At the point of cooperation and consortia, requiring multidisciplinary programs aligned with roadmaps, a good example of NIST participation is its Office of Microelectronics. This was started about the same time as SEMATECH, in recognition that researchers should not be isolated in disciplinary silos. To counteract this tendency, NIST has mechanisms for coordinating its professional scientific staff to be most effective in addressing the broad needs of a growing industry. The Technology Innovation Program is one mechanism for catalyzing the transfer of technology to industry. For the later stage of rapid growth, NIST participates in standards development, tech transfer, and standard practices, as well as through the Manufacturing Extension Partnership (MEP), a nationwide network of facilities to support manufacturers, especially small firms, in developing their technology.

Providing Infrastructure, Expertise, and Standards

For PV and flexible electronics, Dr. Lin said, the technology is now in the first two stages: discovery/proof of principle, and cooperation/consortia. In the first stage, the industry is researching organic PV and new concepts, such as roll-to-roll manufacturing. For cooperation and consortia, the industry has the Flex Tech Alliance recently created by DoE, and PV partnerships. In both cases NIST works with the relevant parties to provide infrastructure and scientific foundation, measurements, and standards as available to support the technology.

He illustrated how NIST supports an industry through the example of organic photovoltaics. This field includes next-generation photovoltaics—printable and

flexible thin film, organic, and hybrid solar cells—which rely on complex nanostructured shapes with multiple components. Some of the most studied systems, he said, are a mixture of types of materials with nanoscale structures that are not fully known. The efficiencies of devices change from line to line, under different conditions, without a great deal of control or understanding. NIST seeks to help reduce these basic unknowns through sophisticated measuring instruments that range from x-rays and synchrotrons to acoustic surface measurement and scanning tunneling microscopes. The objective is to help the technology developers better understand the materials science that underlie manufacturing behaviors.

“The main points here,” concluded Dr. Lin, “are that the work is multidisciplinary, and that many problems cannot be handled by a single discipline. In addition to our own collaborations, we have a large number of open partnerships that focus on objectivity and on practicing the best science available.”

FLEXIBLE ELECTRONICS

Bob Street
Palo Alto Research Center

Given the research orientation of his organization, Dr. Street said that he would discuss R&D aspects of flexible electronics. The context for flexible electronics is largely the display industry that, until recently, has been dominated by liquid crystal displays and based on conventional processing of thin-film silicon on glass substrate. Cost reduction over the past two decades had been achieved by scaling to larger sizes, with the substrate doubling every 2.5 years. The latest substrates, gen-10, are 10 square meters in area. “For a while now we haven’t known when this scaling will have to stop,” he said, “but it can’t go on much longer. It’s already an enormous challenge to make devices on that size of substrate.”

Toward More Diversity in Display Technologies

The primary applications of these displays have been laptops, desktops, and TVs. Displays are a $100 billion industry, and many people foresee much more diversity in future products, including multiple functions, portability, flexibility, and embedding in other devices. This has created a push for new technology which seems likely to bring a shift in manufacturing and cost paradigms. This shift is likely to move the industry from lithography and batch printing, which are expensive, to digital, roll-to-roll printing; from glass to flexible substrates; from vacuum deposition to solution deposition in the ambient; and to new higher-performance materials and green technology.

This scenario, Dr. Street said, has many parallels with the photovoltaics industry. Many of the changes are driven by the high cost of manufacturing devices that are very large. The interest in organic semiconductors for photovoltaics,

despite their low efficiency, for example, comes from the promise that they can be made very simply from solution without expensive equipment. When that promise will be fulfilled, he said, is still unclear.

He gave three reasons for the shift toward flexible electronics:

• First, they can be used to make devices that are either rugged and lightweight or that can be rolled up. These include e-paper and other portable displays; solar cells; RFID tags and smart cards; unbreakable x-ray imagers and security systems, such as truck scanners.

• The second reason is low cost of manufacturing. Roll-to-roll manufacture is viewed as much less expensive than batch processing.

• Third, they are conformable and stretchable. Promising new uses include medical sensors that can be placed on the skin like a plastic bandage; retinal cameras, which mimic the extremely efficient design of the human eye; and a variety of shaped devices. Roll-up displays and RFID tags are close to market now, and flexible solar cells are already in the market.

“Tens, Possibly Hundreds, of Different Materials”

However, Dr. Street cautioned that the business is in a fledgling stage, with most products still in development. The challenges, he said, are largely those of materials science. For example, in changing a display from glass substrates with amorphous silicon or polysilicon materials and photolithography, to a flexible printed device with new thin-film materials, many new options must be developed. Plastic, steel foil, and elastic substrates all have materials issues to be resolved, such as surface quality, barrier layers, and temperature limits. The electronic performance of amorphous silicon must be matched or exceeded when using newer materials, such as organic TFTs, metal oxides, nanowires, all of which come with their own materials challenges.

“The last 10 years have been a wonderful time for the science of electronic materials,” he said. “It’s all being pushed by the size of the display industry. But we now have a whole host of new issues. There are many tens, possibly hundreds, of different materials with different properties to be investigated.”

Big Competition from Asia

To meet these challenges, Dr. Street said, the United States needs to be the leader in materials research. “Then, when we have a problem,” he said, “we can do the research, make the prototypes, and know that they do work. But getting from there to a manufacturable technology is difficult and expensive, and we don’t do that well.” In Asia, by contrast, displays are not only a big industry, but one that is supported by “a whole ecosystem of equipment manufacturers, materi-

als suppliers, and a stream of new technology that is being created in universities and research centers around the world.”

He closed with a call-to-arms for U.S. industry. “Because the industry in Asia is so big,” he said, “it draws in new technology—from the Palo Alto center, from universities, from start-ups. And they have the manufacturing power. We need to understand that many of the materials in the flexible electronics space are the same as will be used in the next generation of photovoltaic materials. We should ask ourselves how easy it will be for these companies to just shift into solar when the time comes and be very competitive with anything we can do. I think this country needs to take this funnel of research and technology that is presently directed toward Asia and move it back into the United States and ensure that we have an industry here that can be the manufacturing focus for the new technology.”