Flexing silicon’s power: Arrays of tiny silicon solar cells like the one in this photograph are assembled using a transfer-printing technique. These arrays are as efficient as conventional solar cells, which are bulky and rigid. Each microcell in the array is about 1.5 millimeters long and 15 micrometers thick.
John Rogers
Thin but efficient solar cells use one-tenth the silicon of conventional cells.
Conventional solar cells are bulky and rigid, but building lightweight, flexible cells has come with trade-offs in efficiency and robustness. A new method for making flexible arrays of tiny silicon solar cells could produce devices that don't suffer these trade-offs. Arrays of these microcells are as efficient as conventional solar panels and may be cheaper to manufacture because they use significantly less silicon. The tiny solar cells could be incorporated into, among other applications, window tinting, and they might be used to power a car's air conditioner and GPS.
Researchers led by John Rogers, a professor of materials science and engineering at the University of Illinois in Urbana-Champaign, used a combination of etching and transfer printing to create arrays of silicon cells that are one-tenth the thickness of conventional cells. They demonstrated multiple possible designs for solar panels incorporating the microcells, including dense arrays flexible enough to bend around a pencil. "You could roll them up like a carpet, transport them in a van, and unfurl them onto a rooftop," Rogers says.
The process builds on techniques for making flexible electronics that Rogers has been developing over the past few years. First, the Illinois researchers etch bars about 1.5 millimeters long, 50 micrometers wide, and 15 micrometers thick from a wafer of monocrystalline silicon. They use a stamp made of a soft polymer to pick up the microbars and place them on a substrate, which may be glass or a flexible plastic, and then fabricate interconnects. Rogers found that a cell thickness of 15 to 20 micrometers struck a good balance: thin enough to be flexible, but thick enough to be mechanically stable and efficient. Conventional solar cells use a layer of silicon 150 to 200 micrometers thick.
Arrays of the cells have about a 12 percent efficiency. The Illinois researchers increased the arrays' power output by about two and half times by adding concentrators in the form of a layer of cylindrical microlenses. The best solar cells on the market convert more than 20 percent of the sunlight that falls on them into energy.
"This is a nice start at using silicon wafers more efficiently," says Howard Branz, principal scientist in the silicon materials and devices group at the National Renewable Energy Laboratory, in Golden, CO. With their transfer-printing approach, says Branz, Rogers and his group have for the first time demonstrated how such thin cells could be manufactured on large areas.
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are not efficiency but cost of the cell.
BUT if you can 'mass produce' the installation of the cells then this significantly reduces the cost also.
AND if the cells are sited near users rather than in huge desert arrays there is a 35% transmission loss elimination, offering even greater savings.
I had thought rooftop installations were ideal but it appears that ground based 'farms' can be install way more quickly and cost effectively.
For reducing costs, mass roll printed cells avoid any individual wafer handling and are a fraction of the cost of silicon solar cells which till recently over their lifetime consume more energy for production and installation than they ever produce.
companies like aes solar's venture with nanosolar produce roll printed cells like this. They are not thin enuf to stick on windows, which is an innovative idea but they are ideal for solar farms.
Just for your information. We recently performed a feasibility study on the use of transparant / UV resistant polyimide substrates for solar cells. They have some technical + and -. Regarding the cost I am not sure, is there any indication of suggested subtrate cost per m2 solar cell? Thanks either way for this thread.
Regards,
Rodney Bennet
Composite Agency Team
The large spacing is a drawback
Rogers's flexible (transferred) silicon solar cell has a drawback of large spcing between individual cell units. This means that his solar cell should merely have an highest efficiency of: W/(W+d) multiply the efficiency of commercial silicon cells. W is the width of the cell unit and d is the spacing between neighbouring cells.
Inaddition, production cost is another issue confining Rogers's flexible solar cell. In commercial solar cell production, except for the P (n-type) doping, other procedures are very easy and trustable.
hello sir. i want to know about the applications which u have discovered recently .can't it be made for wider use .why can't u use little bit larger not as large as 150-200 millimetres . why can't be of size of 45-50 millimetres . by using such type i think it can be made for wider use .if not please explain me why.i think u will reply me soon.
Great Improvement in Solar Cells
These thin solar cell panels which are flexible will use less material and being flexible can fit to any surface to extract solar energy.
Dr.A.Jagadeesh Nellore(AP),India
Wind Energy Expert
E-mail: anumakonda.jagadeesh@gmail.com
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LDighera
13 Comments
Solar Cell Efficiency
>>>The best solar cells on the market convert more than 20 percent of the sunlight that falls on them into energy.<<<
While 20% efficiency may be reasonably close for the majority of commercially available solar panels, more efficient solar cells are currently available. Spectrolab offers 29.9% efficient Triple Junction (XTJ) Solar Cells.
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TestPilot
13 Comments
Re: Solar Cell Efficiency
There was multiple lab samples that showed 40.8% and 40.7% efficiency. With quite a few companies around offering 30+% efficient cells. But you need to understand that such cells are expansive plus their lifetime expectancy several time shorter compare to monosilicon panels(which is usually 16%-18% efficient). So primarily market is space satellites (life expectancy around 15 years at most plus way bigger budget).
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