INDUSTRYNEWS Printable solar cells
A TEAM OF RESEARCHERS from the University of Chicago and the U.S. Department of Energy’s (DOE) Argonne National Laboratory has demonstrated a method that could produce cheaper semiconductor layers for solar cells. The inorganic nanocrystal arrays, created by spraying a new type of colloidal “ink”, have excellent electron mobility and could be a step towards addressing fundamental problems with current solar technology.
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“With today’s solar technology, if you want to get significant amounts of electricity, you’d have to build huge installations over many square miles,” said team leader Dmitri Talapin, who holds a joint appointment with Argonne and the university. But because current solar cells are based on silicon, which is costly and environmentally unfriendly to manufacture, they aren’t cost-effective over large areas. The challenge for scientists is to find a way to manufacture large numbers of solar cells that are both efficient and cheap.
One possibility to make solar cells more economically would be to “print” them, similar to how newspapers are printed. “You’d use a kind of ‘ink,’ stamped on using a roll technology with a flexible substrate,” Talapin said.
Solar cells have several layers of different materials stacked on top of each other. The team focused on the most important layer, which captures sunlight and converts it into electricity. This layer, made of a semiconducting material, must be able to transform light into negative and positive electrical charges but also easily release them to move further along the material to generate electrical current. Many methods to grow the ICs need high temperatures, but a cheaper approach would be to make them in solution. This, however, requires a precursor that is soluble.
The team developed that precursor using quantum dots. Small grains of semiconductors, suspended in a liquid, are “glued” together with new molecules called “molecular metal chalcogenide complexes.” The process heats the material to about 200 degrees Celsius, much lower than the temperatures required for manufacturing silicon solar
cells. The result is a layer of material with good semiconducting properties.
Inorganic solar cell array Arrays of quantum dots allow fabrication of solar cells by printing and other inexpensive techniques.
“The electron mobility for this material is an order of magnitude higher than previously reported for any solution-based method,” Talapin said.
The team used intense X-rays from the DOE Office of Science’s Advanced Photon Source at Argonne to watch as the semiconductor film was created.
“We believe that we could make very competitive solar cells with these nanoparticles,” Talapin said.
Talapin said the success played on the complementary partnership between the University of Chicago and Argonne’s Center for Nanoscale Materials. “At the university we have great students and postdocs who can do a lot of the theoretical chemistry, which requires a lot of manpower,” Talapin said, “but Argonne is a fantastic place to do research that requires sophisticated instrumentation and infrastructure.”
The paper, “Band-like transport, high electron mobility and high photoconductivity in all-inorganic nanocrystal arrays”, was published in Nature Nanotechnology. The research was supported by the Office of Naval Research and a National Science Foundation CAREER award. Work at the Centre for Nanoscale Materials and the Advanced Photon Source was supported by the DOE’s Office of Science.
The Centre for Nanoscale Materials at Argonne National Laboratory is one of the five DOE Nanoscale Science Research Centers (NSRCs), premier national user facilities for interdisciplinary research at the nanoscale, supported by the DOE Office of Science. Together the NSRCs comprise a suite of complementary facilities that provide researchers with state-of-the-art capabilities to fabricate, process, characterize and model nanoscale materials, and constitute the largest infrastructure investment of the National Nanotechnology Initiative.
“After the boom year of 2008, we have recorded a decrease for the second consecutive year” said Robin Welling, ESTIF President. He added: “The solar thermal industry has experienced the full impact of the 2008 financial crisis as the construction sector has been particularly affected by the economic recession that followed. We expected to derive some benefit from the combined implementation of the binding renewable targets and higher energy performance standards – but this process is only beginning!”
The German market, while still the largest in Europe, has dropped by nearly 29% in 2010. The other main markets, such as Italy, Spain, Austria, France and Greece, have behaved very differently in 2010. While both the Greek and Italian markets slightly increased with the Italian market confirming its 2009 level (around 500 000 m2
), other markets such as
Austria, Spain and France suffered a decline.
Some developing markets, still below 200 000 m2
but above 50 000 m2 , grew
a total of 8.8%. This group consists of Portugal, Poland, Switzerland, Czech Republic, Denmark and the United Kingdom. However, their combined increase of 40 000 m2
does not quite
compensate for the decrease recorded in larger markets.
Solar heating and cooling market
THE EUROPEAN SOLAR THERMAL INDUSTRY FEDERATION (ESTIF) released the latest market statistics for the 27 EU member states and Switzerland. Although the European solar thermal market has again experienced an overall decrease in 2010, it still remains above its 2007 level with a total of 2 586 MWth of newly installed capacity.
www.solar-pv-management.com Issue VI 2011
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