- Home -

- Forum -

Nanosolar Solar Cells:  Cheaper than Milk? 

continued from page 1

by Chris Devaney

Enter the 70’s.  Casually ensembled in one of those highly flammable leisure suits of the period and reading Mother Earth News from the back seat of a VW bus (I had some difficulty entirely escaping the 60’s), I too, believed a miracle was about to unfold.  I recall some of Exxon’s claims of a new age of solar energy using film-fed polycrystalline silicon drawn through sapphire dies at an unbelievably fast rate... cheaper than gas, electricity for pennies!  So excited was I that I even interviewed with the company in 1974.  It was, of course, the time when we all began to think seriously again about domestic energy supplies for the first time since WWII.  It, too, seemed only to stall and ultimately increase in cost along with everything else.

But somehow, this time, it just seems different.  Could this really be the dawn of a new era?  Considering that Nanosolar was able to attract highly visible, deep-pocketed investors like the Google boys, Larry and Sergey; serious guys with new-market savvy, these boys are not afraid to look at something in a novel way...and throw money at it.  The company has also been successful in getting millions from the U.S. Department of Defense budget ...yes, D.O.D, in wartime, through Defense Advanced Research Projects Agency funding even though it is not dangerous to other humans, non-explosive, and probably not as useful in war as in peace.  In addition, they have acquired the largest to date financial commitment emanating from the president’s Solar Initiative program.  And there are more investors, plenty more, so stuffed with capital is the company that they are not taking on any new investors at this time.  I should have such problems!  From a financial standpoint alone, Nanosolar certainly stands proud above its competition and worth taking a look at.  Maybe even preparing T-shirts ready to herald Nanosolar as the ultimate sultan, the ubiquitous master cylinder, the harbinger of “the new electricity” and indicating I was there in 2008!  In any case, new dawn or not, without a doubt, Nanosolar has the silicon people scrambling.  And this is good news across the board for photovoltaic consumers.

Nanosolar also takes a unique perspective in hiring a new breed of talent.  Few revered semiconductor gurus roam Nanosolar’s plant, rather “new hires” are youngsters, kids with spanking-fresh ideas not yet molded in “that’s how it has always been done” operatives.  Nanosolar uses the enthusiasm and energy of these engineering doelings to do things the kids didn’t even know were impossible.  And it seems they have done it.  Says Martin Rocheisen, Nanosolar’s CEO, regarding innovation spewing from the bowels deep within the secret Nanosolar development labs, “...[innovation is] mostly driven by smart kids straight out of school who we give all the tools and toys to try crazy new things; plus just a thin dose of managers who know how to earn their respect.”  Being among creative homesteaders here at Homestead.org, I find it odd that this is such a new perspective... for any of us housing a young colt that wants out of the corral, goats, chickens, or a preschooler intent on learning the inner secrets lurking within mom’s new easy-to-reach colorful purse knows the recipe: youth + energy + 3 cups of inquisitiveness, mix with opposable thumbs or tactile lips and hooves, sprinkle in some unflinching persistence and limited supervision  - Presto! - you end up with a sure-fire recipe for success.

At Nanosolar, I picture a lab full of young whippersnappers, energy drink in one hand, palm pilot in the other and ready to attack Hell with a bucket of water.  I call it “The Whippersnapper Effect”.  This approach is pretty much guaranteed to achieve something, maybe even success, but anything is better than the pre-Nanosolar cascade into ever-more expensive solar alternatives.  But with Google’s, Larry and Sergey, hurling gobs money at young colts and whippersnappers, you can bet that nothing is going to stand still in the upcoming solar wars.

How can a young upstart renegade company like Nanosolar, born in 2002, take on, and apparently clobber, the silicon industry in such a surprisingly short development time?  How can it sneak to market a third generation solar technology that was not supposed to be ready until the next decade without the silicon scientists knowing?  Think about it, silicon, the granddaddy of the solar industry whose technology is fed from the fallout of the massive research and development achievements in the electronics industry, where more is known about silicon than even the air we breathe... how can this happen?  Perhaps we should look to the new technology for the answer.  But first...

A Little Side Business

CIGS has been around for around for a while, and was well known as a good prospect for giving the silicon solar technology a run for its money.  It has a lot going for it as a solar cell material but there were some thorny issues as well, especially early on, that made production scale CIGS devices a difficult proposition, a second or even third generation technology that’s not quite ready for prime time solar activity.  Still, a few companies like Shell and Würst Gmbh in Germany are currently producing thin-film solar cell modules from CIGS with respectable efficiency using more or less “conventional” semiconductor vapor phase deposition processes, but not in large quantities. And they haven’t shaken up the world.

Twenty years ago scientists found copper indium diselenide (CIS) to have some pretty unique properties that made it attractive as a solar cell material.  It had a whopping-big absorption of solar energy compared to silicon, so it could be made into thin-film devices that are 1/100th the thickness of crystalline silicon devices. Thin-film devices cut down on kerf losses and labor intensive processing since much of the internal device structure can be “grown-in” in a single step as opposed to multiple post-growth steps.  Thinner devices, less material waste, fewer processing steps, all combine in a nice way to yield a lower final cost.

In addition, CIS has a unique but complex defect chemistry whereby electronic properties of the semiconductor are determined by native defects. This means that the electronic makeup of the PN junction, the actual heart and soul of the solar cell, is determined, not by added impurities as is the usual case, which create many, many difficulties in a semiconductor like silicon, but by the presence or absence of atom vacancies, places where atoms should be, but aren’t and places where atoms shouldn’t be, but are, squeezed interstitially between the belonging atoms.  These vacancies and interstitials create the electrons and holes which are the worker bees in the hive of the semiconductor.  Native defects are more predictable in behavior and, once understood, are somewhat easier to control by annealing or heat treatments.  In fact, CIS shows a remarkable tolerance to unintentional impurities and grain boundaries that otherwise would create havoc in a solar cell.

On the thorny side, early work on the CIS system showed the material to be a tad unstable.  It turns out that the optimum composition of CIS for solar absorption has a copper concentration between 22 and 24 percent. This is all well and good at the growth or deposition temperature but as the thin film is brought down to room temperature all Hell breaks loose and the alloy becomes unstable.  An existence region problem... a material scientist’s nightmare!

 Previous   1   2  3  4    Next