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An EMPA researcher holds a thin film solar cell.  (Source: EMPA)

CIGS efficiency has trended upwards over the last decade and are expected to continue to rise towards the levels of traditional silicon panels.  (Source: EMPA)

Flexible film cells could be worked into ski jackets and other wearables to provide power for electronics on the go.  (Source: Google Images)
Swiss researchers reach a record 18.7 efficiency with a flexible film cell design

Imagine having pants that charged your phone automatically, a ski jacket that charged your MP3 player, or a backpack that charged your laptop.  All of these scenarios sound great, but they all require a power source.

Solar power is one of the most promising solutions for charging low-power electronics on the go, but current cell designs are either inflexible (making them not conducive for wearable applications) or have low efficiencies.  So that perfect solar vest of your dreams hasn't become reality quite yet.

But a team of researchers at the Swiss Federal Laboratories for Materials Science and Technology (EMPA) have, at last, announced [PDF] a new record-efficient flexible film cell that almost matches silicon cell efficiency, opening the door to a wealth of commercial opportunities.

I. Record Efficiency Reached

The scientific community's dedication to solar power has yielded a lot of valuable progress over the past several decades.  This progress has tended to be iterative rather than revolutionary.

Silicon photovoltaic panels slowly crept up to efficiencies where they became financially feasible for power generation.  Now flexible film cells are making a similar climb.

The goal of the EMPA team was two-fold -- first to improve the base efficiency of flexible films and secondly to improve their manufacturability.

Pairing with FLISOM, a start-up company who is scaling up and commercializing the technology, the EMPA team were able to milk out 14.1 percent efficiency by 2005.

The EMPA team's designs focused on Copper indium gallium (di)selenide (CIGS) cells.  The CIGS metal film tended to be a promising material for flexible cells.  While the element indium remains expensive, none of the ingredients are exceedingly rare -- an issue for more novel chemistries.

Since 2005 researchers elsewhere have achieved efficiencies of up to 17.5 using a CIGS film deposited on a steel film substrate.  However these cells required expensive, hard to manufacture diffusion barriers.  They also required a 550°C growth temperature.

II. Cool Runnings -- New Cells Offer Several Improvements

The EMPA team has been hard at work coming up with a simpler design.

Their most recent work shows efficiencies of 18.7 percent being reached without a diffusion barrier.  Better yet, the awesome results were obtained from a film grown at a far lower temperature than past designs.  States research lead Ayodhya N. Tiwari, "Our results clearly show the advantages of the low-temperature CIGS deposition process for achieving highest efficiency flexible solar cells on polymer as well as metal foils."

The results could be game changing as they show a thin film that's almost as efficient as the ~20 percent efficiency of the average traditional silicon panels.  

States Professor Tiwari, "The new record value for flexible CIGS solar cells of 18.7% nearly closes the "efficiency gap" to solar cells based on polycrystalline silicon (Si) wafers or CIGS thin film cells on glass. [F]lexible and lightweight CIGS solar cells with efficiencies comparable to the "best-in-class" will have excellent potential to bring about a paradigm shift and to enable low-cost solar electricity in the near future."

While some applications like wearable electronics are obviously of high interest, the highly efficient thin-film cells could even be eyed as a replacement for traditional cells in solar windows,solar-shingles, or ground-based solar installations.  

A thin film could drastically reduce maintenance costs by reducing the weather and sediment related wear by replacing the relatively fail glass-like silicon with hardy plastics or metal films.

III. What's Next?

The EMPA team is looking to continue to bump efficiencies even higher.  But at this point they're also working to commercialize the tech via FLISOM.  The team is currently working to scale up the low temperature deposition process for mass production.

The work is funded by the Swiss National Science Foundation (SNSF), the Commission for Technology and Innovation (CTI), the Swiss Federal Office of Energy (SFOE), EU Framework Programmes, and two private firms -- W. Blösch AG and FLISOM.

Much of the details on the process remain unpublished and proprietary, unlike traditional university research, in which more information is shared.  Nonetheless, EMPA was quick to release a press release boasting of the record 18.7 percent efficiency, much as a university research team would.

As the technology becomes more established, more details about the precise process improvements should be shared.

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When does this become viable?
By Cr0nJ0b on 5/24/2011 12:22:13 AM , Rating: 2
I'm wondering at what efficiency level Solar becomes truely viable for more than 50% of the states in the US? I mean, today I can buy solar, but it's way to expensive and the payback is too long for my cost/time horizon. At what level does this become a 1 year payback?

By icanhascpu on 5/24/2011 2:13:50 AM , Rating: 2
Whats with the arbitrary numbers? 50% of the stats? huh?

I think its mostly upto the person/small areas for a long time to come. Look at how often you have sunny days, the cost of the installation over average years of usability, to projected cost of standard power over the same amount of time. Its an investment like anything else.

In the mean time Im hoping Nuclear will become more prominent in the larder city+ scope, and the ignorance surrounding it, less so.

Even when solar is a good fit for your area, it usually is not enough to cover the power need of an average home. However, as homes separate items within become smarter and more power efficient (sup dave) and as solar becomes better, they will eventually converge.

Mainly in areas with less sun, the advancement of battery storage will be a huge need for solar to be widely successful.

RE: When does this become viable?
By Wolfy747400 on 5/24/2011 6:41:46 AM , Rating: 2
I'd say we're about 20 years from wacking up solar panels on our roofs which will be able to power everything in our home. During the night, wouldn't have a clue tho..

RE: When does this become viable?
By gamerk2 on 5/24/2011 10:03:59 AM , Rating: 2
1: Moonlight works just as well [reflected sunlight]
2: You are still connected to the main grid

I like starting at my power bill each month; LIPA pays me for power. Plus, helps resale value, which is a must in this type of market...

By geddarkstorm on 5/24/2011 12:54:37 PM , Rating: 2
Only problem with 1. is moonlight is spectrally different from sunlight, far less intense, it tracks across the sky a lot faster, and the moon waxes and wanes: so you won't even get maximal moonlight except a few days out of a year (and conversely, no moonlight for the same amount of time).

Still, you're right that that's often overlooked and can give some amount of power during the night, which is always very useful, especially if we get efficiencies up. But it's nothing you would ever rely upon.

RE: When does this become viable?
By dnd728 on 5/24/2011 6:47:15 AM , Rating: 2
1 year payback is non-realistic, as electricity prices would simply drop long before that - It would be the best investment in town ...yada yada, price drop.

Back to topic, besides efficiency, it obviously depends on price, shape, size…
Large thermosolar plants can more easy return the investment, especially if they're hybrid and capable of using an alternate heat source.
There are also concentrated photovoltaic hybrid systems that are very efficient, but won't easily fit a tiled roof. Search for zenith solar.

RE: When does this become viable?
By nafhan on 5/24/2011 9:24:41 AM , Rating: 2
At what level does this become a 1 year payback?
When the cost of the panels + installation is less than one year of electricity usage... You'll see a lot of people hopping on board well before that point, though. It seems like if we get to a point where payments on a loan to install panels is about the same as the electricity savings (and the panels don't look awful), you would see more people getting on board - especially new construction.

By bug77 on 5/24/2011 4:00:48 AM , Rating: 2
According to wikipedia, solar cells are at almost 29% efficiency (in the lab). That makes them roughly 50% more efficient than flexible ones. Not exactly a closed gap.

RE: Hmm
By Gurthang on 5/24/2011 8:35:55 AM , Rating: 2
You are confusing the various types of cells. They refered to thin film poly-silicon cells as the comparison not crystaline. It would be unfair to compare rigid and expensive crystaline cells to these hopefully cheap and felxible cells. I mean if you are going to bring out the big guns you might as well be mentioning the hyper expensive concentrated multi-junction cells which are over 40% in the labs now.

RE: Hmm
By fishman on 5/24/2011 8:40:56 AM , Rating: 2
Your consumer grade kyrocera solar cells are around 14% to 16% efficient.

"If a man really wants to make a million dollars, the best way would be to start his own religion." -- Scientology founder L. Ron. Hubbard

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