Scientists at MIT have created a breakthrough solution to one of the biggest problems facing solar cells by mimicking the world's best harvesters of solar energy: plants.
Over time, sunlight breaks down the materials in solar cells, leading to a gradual degradation of devices aiming to harvest the energy in that light. Plants don't have this problem because the chloroplasts in plant cells constantly breakdown and reassemble their light-capturing molecules -- essentially constantly creating brand new molecules.
The scientists have developed self-assembling solar cells that can be broken down and reassembled quickly by the subtraction or addition of a surfactant (similar to the dispersants used on the oil spill). MIT News describe the system as being made up of:
"synthetic molecules called phospholipids that form disks; these disks provide structural support for other molecules that actually respond to light, in structures called reaction centers, which release electrons when struck by particles of light. The disks, carrying the reaction centers, are in a solution where they attach themselves spontaneously to carbon nanotubes. The nanotubes hold the phospholipid disks in a uniform alignment so that the reaction centers can all be exposed to sunlight at once and they also act as wires to collect and channel the flow of electrons..."
When the surfactant is added, all of the components come apart. When it's removed, the components spontaneously reassemble into a "rejuvenated" photocell. After repeated tests where the cell is dis- and reassembled, there was no loss of efficiency. The individual molecules have an efficiency of about 40 percent, around double current solar cells, but testing has been at low concentrations of these molecules, so the overall efficiency of the device was also low.
The scientists think that the individual molecules could theoretically hit 100 percent efficiency. They are currently working to increase the concentration of the device and up the overall efficiency to something much greater.
via MIT News
written by Peter, September 07, 2010
written by Ahren, September 07, 2010
written by Cranford Joseph Coulter, September 10, 2010
written by Phil, October 17, 2010
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