TINY SOLAR FUNNELS

MIT’s solar funnel concentrates solar energy 100 times
Susan Wilson, September 13, 2010 (Green.Blorge)

"Researchers at Massachusetts Institute of Technology (MIT) have developed a solar funnel that will focus solar energy 100 times more than current solar cells. These funnels are composed of two layers of carbon nanotubes that work in concert to capture and focus solar energy.

"MIT researchers Michael Strano, the Charles and Hilda Roddey Associate Professor of Chemical Engineering, postdoctoral associate Jae-Hee Han and graduate student Geraldine Paulus…[say] solar funnels could work as antennas that focus solar energy onto photovoltaic cells. The incredible increase of energy could mean much smaller solar arrays…"

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"At 10 micrometers (millionths of a meter) long and four micrometers thick, these tiny fibrous funnels contain 30 million carbon nanotubes [in two layers with different electrical properties called bandgaps]…The outer layer of the funnel has large bandgaps and the inner layer small bandgaps. The difference in bandgap draws the excitons from the outer layer to the inner where they are concentrated…[T]he team still has to find a material that can be used as a semiconductor to generate electric current…to build a prototype solar cell. Currently the funnels lose 13 percent of their absorbed energy. The team wants to reduce that to one percent…

"Manufacturing facilities exist that could produce the solar funnels and more facilities are being built. The cost of producing nanotubes has steadily fallen. Photovoltaic solar cells using solar funnels could be an inexpensive alternative to today’s solar cells…but the time lag between the science and actual production [will be] fairly long…Incorporating Solar Funnels into the mixture [of other breakthrough MIT solar technologies] could allow cars and buildings painted in [energy-generating colors]…"