Fruit of an Old Idea

April 16, 2008 | 4 Comments

In 1991, an idea to just use a sensitive dye as the reactive agent in solar cells was offered by Michael Grätzel and Brian O’Regan at the École Polytechnique Fédérale de Lausanne. A cell using dye sensitized materials are thought to be much cheaper than silicon chip designs. The idea has been 17 years in the ripening.

Dye sensitized cells are not as efficient as silicon and the dye method is seeing some production as its so much less expensive to fabricate. The catch is that even with the low cost cells, the rigging to support them and the electrical equipment to convert the direct current output to home or grid alternating current make the issue of scale vitally important to become more than just economical, but economical when installed.

That makes the breakthrough that the University of Washington put out all the more interesting. Admittedly, the photovoltaic people could use some press. It’s been really quiet for them with crude oil and biomass to fuel occupying the attention of most people.

Zinc Oxide Coated Nano Sized Conglomerated Balls

Their idea is to use tiny balls coated with dye to absorb the radiation coming in or bounce it over to another ball. The ricochet effect traps more light radiation into stimulation of the dye. Other have tried using rough surfaces, but the full ball approach has significant results – using s sub optimum doping of zinc oxide instead of common state of the art titanium oxide as its more easily worked – the team went from 2.4% efficiency to 6.2% or a better than 250% improvement.

The principle was laid out by leader Guozhong Cao a UW professor of materials science and engineering at the American Chemical Society meeting in New Orleans last week. The idea wasn’t to maximize the overall efficiency to compete at this stage, rather the idea is to improve on the previous “rough surface” efforts and gain an engineered surface to make a full run at overall efficiency when the technology is more developed.

Conglomerated Balls with Visible Kernel Elements

Now you have to click on the photo to get to the higher resolution for the surprise. The ball is a conglomeration of even smaller nano sized balls! The UW press release is calling it (ugh) a “popcorn ball.” The nano sized balls run 15 nanometers and the conglomerated balls 300 nanometers. The internal surface area is increased dramatically, catching much more light.

Professor Cao says, “We first wanted to prove the concept in an easier material. Now we are working on transferring this concept to titanium oxide.” With current titanium oxide cells at 11% and commercially available silicon about 20%, Professor Cao is certainly on to something.

Perhaps the balls, conglomerated to 300 nanometers may get conglomerated again, or another layout may become useful, or layered dyes might be added to use a broader range of the radiation. Nevertheless, one thing is certain, dye sensitized panels have a future, much larger than first thought. Wind and hail could devastate installations of expensive solar panel arrays so much less costly panel forms must come to market. Putting $30 thousand dollars on your roof in the wind and hail zone would make for a crushing insurance premium. The business model needs to get 1000 square feet under a replacement cost of $4000 to make this economic enough that almost all roofs could take part and add electrical energy to the power budget. At better than 20% efficient it would be a can’t miss kind of roof.


4 Comments so far

  1. Riley Pockrus on May 27, 2011 9:25 AM

    Intriguing post. I have been searching for some good resources for solar panels and discovered your blog. Planning to bookmark this one!

  2. Felipa Giessinger on September 7, 2011 9:13 AM

    I’ve just started off a blog, the knowledge you give on this site has aided me extremely. Thank you for all your time & work.

  3. Riley Pockrus on September 8, 2011 6:36 PM

    Interesting read, perhaps the best article iv’e browse today. We learn everyday cheers to you!

  4. Adrian Falvo on September 11, 2011 5:48 PM

    Nice post! You truly have a wonderful way of writing which I find captivating! I will definitely be bookmarking you and returning to your blog. In fact, your post reminded me about a strange thing that happened to me the other day. I’ll tell you about that later…

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