“We’ve demonstrated that using a crystalline organic film, pentacene, is a promising new approach to developing organic solar cells,” said Bernard Kippelen, professor in the Center for Organic Photonics and Electronics and the School of Electrical and Computer Engineering at Georgia Tech. “In our paper, we show that we’ve been able to convert solar energy into electricity with 2.7 percent efficiency. Since then, we’ve been able to demonstrate power conversion efficiencies of 3.4 percent and believe that we should reach 5 percent in the near future.”

What makes pentacene such a good material for organic solar cells, Kippelen explained, is that, unlike many of the other materials being studied for use in these cells, it’s a crystal. The crystal structure of atoms joined together in a regular pattern makes it easier for electricity to move through it than some other organic materials, which are more amorphous.

2:55:53 PM    

One easy way to reduce total project cost is to simplify systems so they can be installed by an ordinary contractor or even become part of a do-it-yourself project. A manufacturer could do this by designing solar modules that integrate the photovoltaic panel, DC-AC inverter, safety features, and modular wiring into a single device. If all these features are combined, designing the system becomes much easier. You'd simply guestimate the number of panels needed, throw them up on your roof, and connect them to your existing wiring by way of standard electrical wiring. The panels would feed power back into your household wiring. Safety electronics, similar to fault protection power outlets, would sense anomalies such as a short circuit or external power outage and would isolate the solar panels from the electrical grid when needed
10:57:25 AM    

Sargent believes large-area plastic infrared photovoltaics could become a major marketplace within 10 years, depending on how low their cost goes. But they were not the original research target.

"Our first device was an infrared detector, which converts infrared optical signals into an electrical signal," said Sargent. "As a bonus, because we hadn't anticipated that this would work, we found that it was also a good photovoltaic material capable of harnessing the sun's power.

"There are already infrared photovoltaic cells that are not plastic, and there are already plastic photovoltaic materials," he went on. "What we have done for the first time is combine the two to create a plastic infrared photovoltaic material-that has not been done before."

Others have resorted to exotic technologies to scoop up the entire spectrum of energy from the sun. For instance, Sandia National Labs has created a Stirling-engine-based solar dish that it plans to use in 11-square-mile farms that generate as much electricity as the Hoover Dam.

But Sargent argues that his plastic photovoltaic material can be tuned, with almost any variety of embedded quantum dots, to whichever spectrum is required-both visible and infrared nanoparticles-for a full-spectrum solar cell.

"We think it is quite important," said Sargent. "In the past, photovoltaic cells have not harvested that other [infrared] half of the spectrum, but our device does for the first time."

Nanoparticles enhance a material's quantum-mechanical properties because their electrons are confined to a volume smaller than the electron's wavelength.

"In our materials the wavelength of an electron is about 20 nanometers," said Sargent. "But our nanoparticles-the quantum dots that we used-ranged from 2 to 6 nm in diameter. So we were very very strongly squeezing the electrons.

"The size of the nanoparticles determines the wavelength to which your device will be sensitive," he continued. "By making [semiconducting] particles that are only a few nanometers in size, we squeeze electrons down so far that their wavelength properties can no longer be ignored [in our calculations]-it becomes a quantum-mechanical phenomenon, a so-called quantum dot."

Sargent chose the 2- to 6-nm range of nanoparticle sizes in order to cover a nearly continuous band of wavelengths starting in the infrared and extending into the visible. However, he said, for the current demonstration he was just trying to achieve the "world's first," not the world's most efficient. Next, his group has to prove that its design can actually attain the kind of efficiency that would make it competitive with current silicon cells. The current 1-nm surface coating is, Sargent said, "too thick-we need to make it easier for the electrons to escape from the nanoparticles by making the coating thinner."

2:33:03 PM    

EE Times -Plastic chips tap IR, solar power: "Development of a low-cost plastic infrared photovoltaic material by a group at the University of Toronto could herald a major step forward for solar power, its creators believe, by enabling solar-powered systems to also harvest infrared emissions. The material embeds various-size nanoparticles-or quantum dots-in a polymer suspension. "We have designed a plastic device that is physically flexible-you could even paint it onto things by putting it in a solution," said Toronto EE professor Ted Sargent. "However you deposit it, after drying you have a nice, thin, smooth film that provides the basis for an electronic device." Sargent's group had already demonstrated plastic infrared emitter chips, but the new results are detectors. Sargent believes large-area plastic infrared photovoltaics could become a major marketplace within 10 years, depending on how low their cost goes. But they were not the original research target."
2:29:33 PM    

Oil Industry: "In the categories "Production cost" and "Producer profit" the values show a range from Saudi Arabian production to USA production. Naturally, all the other values may vary some as well; these are general estimates. ExpenseAmount Production cost15¢ to 60¢ Producer profit53¢ to 8¢ Refining cost13¢ Marketing cost5¢ Transportation cost15¢ Retailer cost6¢ Refiner, marketer, transp. & retailer profit10¢ US Taxes19¢ Average state taxes23¢ TOTAL$1.59 If you're paying less than $1.59, it probably means that the independent gas dealer on the corner is only g"
3:55:05 PM    

Oil Industry: "US OIL DEMAND, 2004: Over 20 million barrels per day, up from January 2002, when demand was about 18.5 million barrels per day, = 777 million gallons. If lined up in 1-gallon cans, they would encircle the earth at the equator almost 6 times (about 147,000 miles of cans) â014 every day. 55-60% of US consumption is imported at a cost of $50 billion per year, amounting to the largest single element of our trade deficit. In summer 2004, thanks to higher prices, increased demand, and lower production, record trade deficits of more than $50 billion per month were recorded, with approximately 30% of that attributable to imported energy costs."
3:53:06 PM    

SABCnews.com - sci_tech/science: "A team led by Vivian Alberts of the Rand Afrikaans University (RAU) has unveiled a solar panel plant at the Johannesburg campus that produces photovoltaic (PV) panels at a quarter of the cost of current technology. A complete system, which is to generate electricity from sunlight, could be in production within the next three years. The team, made up of physicists from RAU, the University of Port Elizabeth and the University of Pretoria developed an industrial method of producing copper-indium(gallium)-diselenide (CIGS) panels as opposed to the silicon-based technology that are used currently. The world is looking for cheaper energy and physicists say they were in competition with major players in the energy field, like Shell National Renewable Laboratories to invent a cheaper way of converting sunlight into electric energy. "
10:20:32 AM    

GreenBiz News | New Partnership to Commercialize Plastic from Corn: "PHAs are a broad and versatile family of natural plastics that range in properties from rigid to highly elastic, making them suitable for films, fibers, adhesives, coatings, molded goods, and a variety of other applications. While stable to even hot water, they will biodegrade in aquatic, soil and composting environments, and even under anaerobic conditions, once their use is over. They are made using a proprietary process developed by Metabolix that converts renewable and sustainable agricultural raw materials through a fully biological fermentation process"
10:16:09 AM    

GreenBiz News | New Partnership to Commercialize Plastic from Corn: "The new facility, part of a 50/50 joint venture to manufacture and market natural PHA polymers for a wide variety of applications, including coated paper, film, and molded goods. Natural PHA polymers are produced using a fully biological fermentation process that converts agricultural raw materials such as corn sugar into a versatile range of biodegradable and compostable plastics. "
10:15:41 AM    

GreenBiz News | New Partnership to Commercialize Plastic from Corn: "CAMBRIDGE, Mass., Nov. 11, 2004 - Metabolix, Inc. and Archer Daniels Midland Company have agreed to establish a 50,000-ton production facility to commercialize a new generation of high-performance natural plastics from corn. "
10:15:13 AM    

One-third of the Earth's surface is at risk, driving people into cities and destroying agriculture in vast swaths of Africa. Thirty-one percent of Spain is threatened, while China has lost 36,000 square miles to desert — an area the size of Indiana — since the 1950s.

4:59:34 PM    

Products - StorCard Technology: "Performance The StorCard architecture delivers a high level of system performance. Data can be transferred from the card to the reader and delivered to the host or client at 5MB per second with the 100MB product, and will scale with higher-capacity designs. In addition, encryption is done on-the-fly, which frees up the host for other time consuming operations. The card can also authenticate users and their data with involvement from a client or host."
1:44:02 PM    

Products - StorCard Technology: "StorPod A reader mechanism, StorPod, is required to record and playback information from the StorCard similar to a floppy disk drive. The StorPod has electromechanical components such as a 3600 RPM spindle motor, and rotary actuator to spin the flexible disk and position the recording head over the disk surface. Electronics in the StorPod provide the host interface and control functions necessary to record and playback information to and from the StorCard. Standard Smart Cards can be read in the StorPod. The StorPod is constructed as an external unit with a USB interface"
1:43:30 PM    

Products - StorCard Technology: "The StorCard has the flexibility and form factor of a credit card and conforms to ISO 7816-1 including mechanical flexibility along the longitudinal and transverse axis without damage to the IC or the magnetic recording medium. A semiconductor device is mounted on the card similar in construction to the Smart Card. This electronic chip controls the flow of data to and from the card. A flexible magnetic disk is housed inside a cavity created between the top and bottom layers of the card. The StorCard is a laminated structure, with the layers made up of plastic and metal sheets. The outer surfaces of the card have artwork that can be personalized similar to a credit card. A window is provided on the bottom and a shutter that slides between the layers of the card, backs this window sealing the disk enclosure. An external mechanism (in the StorPod) can actuate this shutter opening the window and providing access to the recording disk. When the StorCard is outside the StorPod, the shutter is locked and cannot be opened without special tools."
1:42:58 PM    

Products - StorCard Technology: "StorCard Inc., has developed both the StorCard and StorPod products. StorCard is convenient and secure portable storage media in a credit card form factor. StorPod is a compact electronic reader used to read and record information on individual StorCards. The patent-protected designs of the StorCard and StorPod combine the best features of smart card, disk and security technologies into a new generation of secure portable storage."
1:42:02 PM    

Gallium nitride–based LED may emit white light intrinsically

Two predominant ways to get white light from LEDs now exist. In one, a blue or UV-emitting LED is combined with a phosphor to produce an approximation of the white-light spectrum. In the other, the light from separate blue-, green-, and red-emitting LED chips are mingled to create white. Researchers at North Carolina State University (Raleigh, NC) and the U.S. Army Research Office (Research Triangle Park, NC) have developed a third approach, at least in theory.

Indium gallium nitride/gallium nitride (InGaN/GaN) LEDs can emit blue or green strongly, and red only weakly, with very poor efficiency. This occurs because a large internal field keeps the wave functions of holes and electrons apart; the effect results from a lattice mismatch between the well and the GaN quantum barrier. The researchers propose adding aluminum (Al) to the structure, replacing the GaN barrier with AlInGaAn and tailoring lattice mismatch. Simulations show that, with proper design, a single LED with three structures can produce blue, green, and red light of similar intensity and good efficiency. The researchers would like to fabricate such a device; one possible source of funding is the U.S. Department of Energy program on solid-state white-light sources, when it materializes. Contact Ki Wook Kim at kwk@ncsu.edu.

1:40:28 PM    

Laser Focus World - Newsbreaks
1:37:50 PM    

If made practical, amorphous and polycrystalline sheet solar cells could end up perched atop many a commercial or residential roof. But the devices, which can range up to a square meter in size, suffer from reduced efficiency caused by micron-scale nonuniformities in grain size and chemical composition. Scientists at the University of Toledo (Toledo, OH) have developed a technique in which a thin-film semiconductor structure, when immersed in an electrolyte and exposed to light, modifies itself to compensate for the nonuniformities.

In one example, a cadmium telluride/cadmium sulphide (CdTe/CdS) photovoltaic device contains a 0.15-µm-thick layer of CdS and a 3.5- to 4-µm-thick layer of CdTe on glass. The electrolyte consists of sodium chloride, aniline, and p-toluenesulfonic acid in deionized water. When the electrolyte is applied to one side of the structure and tungsten-halogen lamp light to the other, changes occur that the researchers posit are the elimination of weak microdiodes and the depositing of a protective layer. The process improved the efficiency of CdTe/CdS cells from 1%–3% to 11%–12%. Contact Yann Roussillon at yroussi@uoft02.utoledo.edu.

1:37:16 PM    

Laser Focus World - Newsbreaks
1:34:21 PM