News & Analysis
Low-cost, more efficient solar cells mostly plastic
R Colin Johnson
2/18/2010 1:15 PM EST
PORTLAND, Ore. — By growing arrays of silicon wires in a polymer substrate, researchers have demonstrated what they say are flexible solar cells that absorb up to 96 percent of incident light.
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| Photomicrograph of a silicon wire array embedded within a transparent, flexible polymer film. Credit: Caltech/Michael Kelzenberg |
California Institute of Technology (Caltech) researchers said the wires are made up of 98 percent plastic, potentially lowering the cost of photovoltaics by using just 1/50th the amount of semiconductor material used today. In tests, the experimental solar cells demonstrated over 90 percent quantum efficiency.
"By developing light-trapping techniques for relatively sparse wire arrays, not only did we achieve suitable absorption, but we also demonstrated effective optical concentration," claimed Harry Atwater, director of Caltech's Resnick Institute.
The silicon wires measure just 1 micron in diameter, but can be as long as 100 microns and can be embedded in a transparent polymer. Light is converted into electricity only inside the wires, but light not immediately absorbed bounces around inside the matrix until it enters another wire. The result, researchers said, is both high concentration and high efficiency in the material.
Solar cells based on the technique could potentially be very inexpensive to manufacture since only 2 percent of the materials are expensive semiconductors while the remainder is made from inexpensive plastic.
The new material is about the same overall thickness as a conventional solar cells--about 100 microns--but contain as much silicon as a solar cell measuring just 2 microns in thickness.
Atwater said he is now working to increase the operating voltage and size of the solar cells so that they can eventually be manufactured in flexible sheets using inexpensive roll-to-roll fabrication equipment.
Funding for the Caltech research was provided by BP, the U.S. Energy Department, the National Science Foundation and the Kavli Nanoscience Institute at Caltech.
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Cablemen
2/20/2010 3:05 AM EST
What is the estimated cost per watt that someone may hazard a guess on for say some 200 watt panels when they are developed for industry to install?
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asdasdsa45646456
2/22/2010 3:27 PM EST
Plastic is a petroleum byproduct. So how much oil will be used to make these?
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CSR88
2/27/2010 5:22 AM EST
This is very interesting indeed. We understand that this is early stages, but still I would love to see some numbers to compare to the traditinal cells. Also when do you anticipate to get this into manufacturing, assuming this is possible?
Thanks
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blue7053
3/23/2010 4:38 PM EDT
Solar cells are currently selling for $.98 (98 cents/watt) by the pallet (~20/pallet). The great majority are selling for ~$2/watt as sgl panels. Available as from 12 volt to 600v systems.
http://www.ecobusinesslinks.com/solar_panels.htm
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prabhakar_deosthali
12/30/2010 12:08 AM EST
Apart from the cost, it is the flexibility of the plastic material that will make the solar panel being used in many more places- like car bodies could be layered with such material to produce electricity to charge the car batteries. You could just hang such solar panels on a rope in your backyard when there is sunshine and get electricity.
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Winnipegger
4/12/2011 2:57 PM EDT
What does "quantum efficiency" mean? A paper published in year 2000 stated Gallium-Indium-Nitride semiconductor photovoltaic cells were able to convert 56% with 2 junctions, 64% with 3 junctions, or 72% with 36 junctions. A later paper optimized this, the researcher calculated 70.2% conversion with 8 junctions. But that is a percentage of all sunlight that strikes the cell. That chemistry has the advantage that every junction uses the same chemicals, each junction is transparent to colours that it doesn't convert to electricity. Each junction has a different concentration of nitrogen to absorb different colours. Initially they had difficulty getting nitrogen to permeate the cell, but later research solved that problem. Unfortunately no one has commerciallized this technology. Now this article claims 90%, but what exactly is "quantum" efficiency?
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