Northwestern Univ. team’s coating may improve solar cells
BY Jon Van, March 3, 2008
Source: Chicago Tribune
http://www.chicagotribune.com/technology/
chi-mon_notebook_0303mar03,1,6604444.story
Efforts by Northwestern University scientists to boost the efficiency of plastic-like flexible solar cells could make the technology commercially viable. Researchers have demonstrated a 40 percent efficiency increase in organic photovoltaic cells and believe that with further work they can raise that output significantly. Flexible solar panels could be manufactured cheaply using technology similar to printing newspapers or the packaging used for potato chips, said Tobin J. Marks, an NU chemistry professor who co-leads the research team with Robert Chang, a materials science professor.
Lightweight flexible materials that convert sunlight to electricity could be extremely useful in reducing our reliance on fossil fuel energy sources that expel carbon dioxide and other greenhouse gases. “You could incorporate flexible organic photovoltaics into roofing shingles,” said Marks, describing how the material might be used to generate electricity for homes.
In remote areas where electricity is unavailable, sheets of flexible photovoltaics might be spread out under the sun to produce electricity to charge cell phones and other wireless gadgets.
Many scientists contend that photovoltaic farms covering hundreds of square miles of American desert could generate the bulk of the nation’s electrical power needs. The most recent proposal appeared in January’s issue of Scientific American. These proposals envision using rigid solar panels made from silicon, but flexible organic technology would be cheaper and more rugged, Marks said. At present, silicon photovoltaics are more efficient than flexible organic solar panels, but that could change as organics improve.
Northwestern researchers achieved their success by coating one of the solar cell’s electrodes, the anode, with an ultrathin layer of nickel oxide. This nanocoating kept errant electrons from diluting the solar cell’s function. The active component of a flexible photovoltaic consists of two organic compounds that become excited when struck by photons of light. When exposed to light, the compounds give off negatively charged electrons and their positively charged counterparts that scientists call holes.
The goal is for electrons to head for the electrode called the cathode and the holes to go to the anode, setting up a flow of electrical current. The nickel oxide nanocoating lets holes through, but repels electrons to make electricity flow as intended. NU researchers have filed to patent their discovery and believe they can refine the process to further improve it. “We see this as more than an incremental improvement,” Marks said. “We see it as a breakthrough.”
Understanding bees: The price of analyzing genetic material is dropping as biotech firms seek to make individual genetic analysis more affordable, and this has had an interesting side effect. In understanding honeybees. Using inexpensive DNA analytic technology, researchers at the University of Illinois at Urbana-Champaign have turned their attention to various honeybee species and found a lot of cross-breeding. African bee species, sometimes called killer bees for their aggressive stinging, have spread their genes to species of less aggressive European honeybees prized by humans.
The researchers, professor Charles Whitfield and postdoctoral scientist Amro Zayed, found that when bee DNA mixes, it isn’t random. Active DNA from European bees was found in hybrids with Africans more often than inactive DNA. The full import of this finding, what effect this may have on honeybee behavior, isn’t yet clear, said Whitfield, but the research takes a step toward finding relationships between genetics and behavior in bees.
Given the economic importance of honeybees to agriculture, this could turn out to be of more than academic relevance. In the Midwest, few feral honeybees survive these days, bee mites and disease having taken a toll. Most Midwest bees come from commercial beekeeper supply operations. “It’s kind of like domestic cattle,” said Whitfield. “The gene pool of honeybees isn’t very diverse. Unlike cattle breeding, beekeeping is low tech.”
In warmer states, feral honeybees survive and are predominantly Africanized hybrids. At about the time European species were weakened by disease and mite infestations, African bees arrived from South America. “It was a quick switch-over,” Whitfield said. “Almost a flip from no African to mostly African in just a few years.”