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Posted: May 10, 2006
Advancements in printable solar cell research using carbon nanotubes
(Nanowerk News) Eikos Inc., a developer and licensor of highly transparent carbon nanotube (CNT) inks for conductive coatings and circuits, and the National Renewable Energy Laboratory (NREL) have achieved competitive efficiency in two types of solar cells using carbon nanotube conductive coatings, in a significant step toward developing fully printable solar cells.
NREL/Eikos created organic solar cell structures which achieved an efficiency of 2.6% – making them competitive with commonly used Indium Tin Oxide (ITO) transparent conductors. Organic photovoltaics (OPVs) using carbon nanotubes are an attractive alternative to traditional silicon-based solar cells because they are inexpensive and abundant, can be manufactured more efficiently and are both lightweight and flexible.
Today, both ITO and PEDOT are used as transparent electrodes in organic cells. However, Indium Tin Oxide layers are expensive to fabricate, and Indium is costly to acquire and is only available in limited quantities. ITO is also optically, electronically and chemically problematic. PEDOT:PSS has limitations since it is known to degrade under UV illumination, introduces water in to the devices active layer, and retains a degree of acidity.
As part of the U.S. Department of Energy Contract through which the solar research is being conducted, NREL/Eikos also produced the world s first thin-film Copper Indium Gallium diSelenide (CIGS) solar cell incorporating CNTs, with a significant 12.98% energy conversion efficiency using its Invisicon® transparent coatings instead of doped Zinc Oxide. Using an aluminum doped Zinc Oxide transparent electrode, the record efficiency is thought to be 19.5%
According to program manager Jorma Peltola, These are exciting developments for the solar community which is now one step closer to achieving a fully printable solar cell. Our Invisicon® technology will provide equal efficiency to conventional cells, at less than half the cost, with less weight and more flexibility. Eikos/NREL is proud to be spearheading research that could harness cleaner, more abundant solar energy resources.
Aspects of this research are slated to be published in a major journal in the near future. The article is coauthored by NREL of Golden, Colorado and Eikos of Franklin, MA.