Competitive Solar Cells at 25% of Typical Cost

The lower costs of manufacturing may give dye-sensitized solar cells an important niche in a rapidly growing market.

Grätzel and o’Regan first demonstrated a DNSC (Dye-sensitized Nano-structured Solar Cell) in 1991. There since had been slow improvement in light-to-energy conversion efficiency. Recently, Dyesol announced such progress in development that a dye-sensitized solar cell could be considered competitive with other means of producing solar electricity. Other announcements have followed.

Autoblog Green relays an Engadget report that Ohio State University researchers claim efficiency from a new type of cell as good as “the normal silicon based cells currently on the market.” One might assume that the author is referring to photo voltaic cells made from amorphous silicon. “The dye-sensitive solar cells appear pink due to the mixture of ruthenium and either titanium or zinc oxide particles in the cells.”

The very good news is that such solar cells would cost about a quarter of the price. as other competing cells. As previously noted, material scientists have focussed upon SAMs (Self Assembled Mono-layers) of metal complexes. More recently, researchers at Rice University announced a new recipe for better, cheaper photo voltaic solar cells. It promised sufficient stability for mass production and used less expensive materials.

U.Deleware researchers Christiana Honsberg and Allen Barnett
Photo by Carlos Alejandro

U.Deleware researchers Christiana Honsberg and Allen Barnett

Production is ramping up because of the current scarcity of pure silicon. Jim Fraser maintains a list of manufacturers of low cost fairly efficient solar panels that includes Daystar, Global Solar, HelioVolt, Honda, Konarka, Miasole, Nanosolar and Q Cells. Konarka, in particular, has been scaling up its dye cell technology to large-scale production capabilities since 2006.

Fairly efficient to Fraser is above 12%. The best silicon solar cells generally available commercially are 22% efficient at converting sunlight that hits them into electricity.

The University of Delaware has achieved a record-breaking combined solar cell efficiency of 42.8% from sunlight at standard terrestrial conditions. A DARPA funded consortium led by the University of Delaware used multiple innovations to achieve this very high-performance with a crystalline silicon solar cell platform.

2 Comments

jcwinnie

Posted 2008-3-13 at 10:52 am | Permalink

Since dye-sensitized solar cells can be made cheaper than silicon cells, there is considerable development underway. For instance, Michael Gratzel is working on more advanced versions.

Via the Big Gav, we learn from Prachi Patel-Predd about “a new combination of electrolyte and dye promises to make these solar cells even cheaper and more robust.”

In a paper published in the online edition of Angewandte Chemie, Gratzel, a chemistry professor at the École Polytechnique Fédérale de Lausanne in Switzerland, presents a version of dye-sensitized cells that could be more robust and even cheaper to make than current versions.

Dye-sensitized solar cells consist of titanium oxide nanocrystals that are coated with light-absorbing dye molecules and immersed in an electrolyte solution, which is sandwiched between two glass plates or embedded in plastic.

Light striking the dye frees electrons and creates “holes”–the areas of positive charge that result when electrons are lost. The semiconducting titanium dioxide particles collect the electrons and transfer them to an external circuit, producing an electric current.

…

In existing versions of the solar cells, the electrolyte solution uses organic solvents. When the solar cells reach high temperatures, the solvent can evaporate and start to leak out. Researchers are now looking at a type of material that may make a better electrolyte: ionic liquids, which are currently used as industrial solvents. These liquids do not evaporate at solar-cell operating temperatures. “Ionic liquids are less volatile and more robust,” says Bruce Parkinson, a chemistry professor at Colorado State University.

New dyes are also being investigated. In commercial cells, the dyes are made of the precious metal ruthenium. But researchers have recently started to consider organic molecules as an alternative. “Organic dyes will become important because they can be cheaply made,” Gratzel says. In the long run, they might also be more abundant than ruthenium. …

Parkinson cautions, though, that work on organic-dye solar cells is still at a very early stage. Going from a laboratory prototype to a commercial module typically reduces efficiencies significantly.

To capture a larger share of the solar-power market, dye-sensitized solar cells will require some more improvements. “We really need a breakthrough to get up to 15 percent efficiency in the lab,” Parkinson says.
jcwinnie

Posted 2008-4-10 at 5:53 pm | Permalink

Helena, Montanna Trehugger Tim McGee also relays a news story from the University of Washington about a potential doubling in the efficiency of which dye-sensitized solar cells (also known as Grätzel cells) are capable.

We recently covered how Shaik Zakeeruddin and Michael Grätzel used ionic liquids to make these solar cells flexible and significantly less toxic. Today we learn from the University of Washington (UW) that it’s possible to double the efficiency of dye sensitized solar cells by using a novel popcorn-ball design.

Photo Credit to University of Washington.
“We think this can lead to a significant breakthrough in dye-sensitized solar cells,” said lead author Guozhong Cao, “We did not expect the doubling…it was a happy surprise.”

Cao, a UW professor of materials science and engineering did not set out to increase the maximum efficiency of dye sensitized solar cells. Instead, his team was investigating the difference in how light is absorbed using different processing and design techniques.

The problem with absorption in dye sensitized solar cells is that you not only want to provide a lot of surface area where light can interact, but you also want the light to have multiple ‘attempts’ at interacting with one of the dyes. The new solar cell strategy takes advantages of a hierarchical (or fractal if you prefer) design to achieve both goals.

At the smallest scale, Cao and his team developed 15 nanometer diameter ‘grains’ of the solar cell material. The small grains are then clumped together to form aggregate clusters that are about 300 nanometers across (175 of these clusters lined up are about equal to the width of a human hair). The complex internal structure created within the clusters creates tremendous surface area for light to interact with the dye, about 1000 square feet for each gram of material. Yet, at the same time the larger (300 nanometer) structures scatters more light within the entire solar cell creating more opportunities for interaction with other clusters.

The new design vastly improved the efficiency of the dye sensitized zinc oxide cell Cao was working with for this experiment, from 2.4% to 6.2%. Dye sensitized solar cells today traditionally use Titanium dioxide, and can achieve efficiency conversions around 11%.

“We first wanted to prove the concept in an easier material. Now we are working on transferring this concept to titanium oxide,” Cao said.

Cao and team think their new design will also increase the efficiency of titanium dioxide dye sensitized solar cells. If the results are similar to what was achieved in zinc oxide, we may see a 20% efficient dye sensitized solar cell in the near future.

Dye sensitized solar cells are cheaper to produce and easier to manufacture than traditional silicon PV cells. Dye sensitized solar cells also offer low toxicity, creative, flexible, and increasingly efficient designs. The future looks bright for the dye sensitized solar cell to play a significant role in our energy matrix.

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