Solarmer Energy Inc. expects sun to shine on Chicago invention

	University of Chicago chemists Luping Yu (right) and Yongye Liang display a new material they synthesized called PTB1. The University of Chicago has licensed the material to Solarmer Energy Inc., which is developing plastic solar cells for portable electronic devices. (Lloyd DeGrane)

Solarmer Energy Inc. is developing plastic solar cells for portable electronic devices that will incorporate technology invented at the University of Chicago.

The company is on track to complete a commercial-grade prototype later this year, said Dina Lozofsky, vice president of IP development and strategic alliances at Solarmer. The prototype, a cell measuring eight square inches (50 square centimeters), is expected to achieve 8 percent efficiency and to have a lifetime of at least three years.

"New materials with higher efficiencies are really the key in our industry. Plastic solar cells are behind traditional solar-cell technology in terms of the efficiency that it can produce right now," Lozofsky said. "Everyone in the industry is in the 5 percent to 6 percent range."

The invention, a new semiconducting material called PTB1, converts sunlight into electricity. Inventors Luping Yu, Professor in Chemistry, and Yongye Liang, a Ph.D. student, both at the University of Chicago, and five co-authors describe the technical details of the technology in an online article published Dec. 18, 2008, in the Journal of the American Chemical Society.

"Yongye is very knowledgeable and skillful. Very creative," Yu said. "He is mainly responsible for the progress of this project."

The active layer of PTB1 is a mere 100 nanometers thick, the width of approximately 1,000 atoms. Synthesizing even small amounts of the material is a time-consuming, multi-step process. "You need to make sure what you have is what you think you have," Yu said.

The University licensed the patent rights to the technology to Solarmer last September. The license covers several polymers under development in Yu's laboratory, said Matthew Martin, a project manager at UChicagoTech, the University's Office of Technology and Intellectual Property. A patent is pending.

An advantage of the Chicago technology is its simplicity. Several laboratories around the country have invented other polymers that have achieved efficiencies similar to those of Yu's polymers, but these require far more extensive engineering work to become a viable commercial product.

"We think that our system has potential," Yu said. "The best system so far reported is 6.5 percent, but that's not a single device. That's two devices."

By combining Solarmer's device engineering expertise with Yu and Liang's semiconducting material, they have been able to push the material's efficiency even higher. Based in El Monte, Calif., Solarmer was founded in 2006 to commercialize technology developed in Professor Yang Yang's laboratory at the University of California, Los Angeles. The company is developing flexible, translucent plastic solar cells that generate low-cost, clean energy from the sun.

Yu began working with Solarmer at the suggestion of UCLA's Yang, a professor of materials science and engineering. Yu's research specialties include the development of new polymers, long chains of identical atoms that chemists hook together to form plastics and other materials.

Yu's research program includes funding from the National Science Foundation and a Collaborative Research Seed Grant from the University of Chicago and Argonne National Laboratory. Solarmer has entered into a sponsored research agreement with the University to provide additional support for a postdoctoral researcher in Yu's lab. The company looks forward to the identification of new polymers as a result of this collaboration, Lozofsky said.

Silicon-based solar cells dominate the market today. Industry observers see a promising future for low-cost, flexible solar cells, said UChicagoTech's Martin. "If people can make them sufficiently efficient, they may be useful for all sorts of applications beyond just the traditional solar panels on your house rooftop," he said.

Physicists harness effects of disorder in magnetic sensors

	University of Chicago physicist Thomas Rosenbaum, with the helium dilution refrigerator in his laboratory, where he observes the quantum behavior of materials chilled to temperatures approaching absolute zero. (Dan Dry)

University of Chicago scientists have discovered how to make magnetic sensors capable of operating at the high temperatures that ceramic engines in cars and aircraft of the future will require for higher operating efficiency than today's internal combustion technology.

The key to fabricating the sensors involves slightly diluting samples of a well-known semiconductor material, called indium antimonide, which is valued for its purity. Chicago's Thomas Rosenbaum and associate Jingshi Hu, now of the Massachusetts Institute of Technology, have published their formula in the September issue of the journal Nature Materials.

Most magnetic sensors operate by detecting how a magnetic field alters the path of an electron. Conventional sensors lose this capability when subjected to temperatures reaching hundreds of degrees. Not so in the indium antimonide magnetosensors that Rosenbaum and Hu developed with support from the U.S. Department of Energy.

"This sensor would be able to function in those sorts of temperatures without any degradation," said Rosenbaum, the John T. Wilson Distinguished Service Professor in Physics.

Rosenbaum's research typically focuses on the properties of materials observed at the atomic level when subjected to temperatures near absolute zero (minus-460 degrees Fahrenheit). More than a decade ago, he led a team of scientists in experiments involving silver selenide and silver telluride, two materials that exhibited no magnetic response at low temperatures. But when the team introduced a tiny amount of silver (one part in 10,000) to the materials, their magnetic response skyrocketed.

In silver selenide and silver telluride, the magnetic response disappears at room temperature, which limits their technological applications. But Rosenbaum and Hu now have used two methods to recreate the effect at much higher temperatures in indium antimonide. Disordering the material-simply grinding it up and fusing it with heat-produces the effect. So does introducing impurities of just a few parts per million.

"What's nice about it is that, first, it's an unexpected phenomenon; and second, it's a very useful one," said University of Cambridge physicist Peter Littlewood. "Normally, in order to make large effects, you have to have pure samples."

Before Rosenbaum and Hu's latest experiments, two theories dueled to explain the effect. In 2003, Littlewood and Meera Parish, now a postdoctoral fellow at the Princeton Center for Theoretical Physics, explained the effect using classical physics, the laws of nature that govern physics above the atomic scale. Nobel laureate Alexei Abrikosov of Argonne National Laboratory devised an explanation based on quantum physics, the dominant physics at ultrasmall scales.

"We've shown that both theories work, just in different regimes," Rosenbaum said.

Littlewood lauded the sequence of events as an example of how science ought to work. "There's a discovery of a result. There's a theory about it. Further experiments are done to test the theory. They work and that provokes another idea, and you bounce to and fro," Littlewood said. "That's how we like to describe science progressing. One is rarely lucky enough to do that over a long period."