Dye Solar Cells

"The ruthenium dye absorbs available solar energy the way chlorophyll does, taking in electrons and transferring them to the titania (Titanium Dioxide) layer to create electricity", from Chris Turner. Thanks to him for writing the article ("Solar Goes Supernova",Fast Company Dec'08/Jan'09 edition) that inspired this lens.

The Dye Solar Cell process can be conceptualized into a few different steps. The photon (incoming light) is absorbed by the electrolyte (Iodine in the example shown). The electron then flows through the Dye (ruthenium) into Titanium Dioxide where the current flows to an external power sink, and then back to the electrolyte solution to regenerate/reconvert the ion.

The facing diagram image from http://www.postech.ac.kr/chem/mras/eunju.htm shows the process in action.

A great resource with additional details can be found at wikipedia on dye-sensitized solar cells.

One of the most amazing, and powerful impacts of dye solar cells is the possibility to integrate electrical energy generation with existing major construction industries. Corus, a major company (formerly British Steel) is partnered to Dyesol to conduct a feasibility analysis for putting dye solar cells into prefinished steel roofing materials (source Chris Turner, thanks again!).

This could result in an order of magnitude increase for renewable energy generation as existing large scale roofing materials could be evolved into working energy creating devices. The question of effective lifetime and maintenance comes into play, but huge potential is there.

The complimentary image shows some sample response curves, incident photon-to-current conversion efficiency (IPCE) vs. wavelength.

Specific detailed response information can be found within this paper "Spectral Response of Opal-Based Dye-Sensitized Solar Cells", published Dec. 13,2007 in The Journal of Physical Chemistry C.

A brief list of some of the key companies focusing on Dye-Sensitized Solar Cell applications:

• Dyesol A company founded in Australia in 1994 that specializes in commercialization of Dye Solar Cell technology.


• Konarka"Konarka's Power Plastic® is made using low cost organic materials (organic photovoltaics, or OPV). Such 3rd generation technologies are rapidly emerging to displace 1st and 2nd generation technologies by overcoming their technical limitations and delivering a truly cost-effective renewable power solution."


• Sony and some
  R&D projects"...Sony practices energy efficiency in many ways. As we seek to reduce energy consumption, we are also actively introducing renewable energy sources free of CO2 emissions."


• Aisin Seiki is working with Toyota on automobile applications


Picture from Good Clean Tech article

You can make your own Dye-Sensitized Solar Cells at home using the Dye Solar Cell Kit

The following paragraph taken from the SOL IDEAS site describes the kit:
"The result of the procedure is a solar cell that lasts no longer than a few months, but yet it can provide insights into basic chemical, biological and environmental processes. It is therefore a teaching tool, and not a practical photovoltaic power module. The dye sensitized solar cell (DSSC) technology was developed in the early 1990s at the Swiss Federal Institute of Technology (EPFL), where Sol Ideas founder Greg P. Smestad received his Ph.D. Its central technical challenge stems from the fact that it is difficult to seal the liquid electrolyte in, and keep atmospheric gases (like water and O) out, over the 10-15 year lifetime of the device necessary for economic viability as a power source. The dye in the TiO DSSC solar cell also degrades unless special Ru-bpy dyes are used. For more about the economics of PV, one can refer to several sources, such as Optoelectronics of Solar Cells. Researchers, such as those at the EPFL, and several companies are working on solid state and ionic liquid electrolytes, as well as sealing methods, to improve the longevity of this thin film PV technology. For more on these topics, visit our links and information page, and go to our publications page."

So what's the big deal? By clumping tiny balls together to make larger spheres the folks at the University of Washington were able to double solar conversion efficiency.

Original ENN article
(some key points)
"We think this can lead to a significant breakthrough in dye-sensitized solar cells," said lead author Guozhong Cao, a UW professor of materials science and engineering. "

"One of the main quandaries in making an efficient solar cell is the size of the grains. Smaller grains have bigger surface area per volume, and thus absorb more rays. But bigger clumps, closer to the wavelength of visible light, cause light to ricochet within the thin light-absorbing surface so it has a higher chance of being absorbed."

"You want to have a larger surface area by making the grains smaller," Cao said. "But if you let the light bounce back and forth several times, then you have more chances of capturing the energy."

"Other researchers have tried mixing larger grains in with the small particles to scatter the light, but have little success in boosting efficiency. The UW group instead made only very tiny grains, about 15 nanometers across. (Lining up 3,500 grains end to end would equal the width of a human hair.) Then they clumped these into larger agglomerations, about 300 nanometers across. The larger balls scatter incoming rays and force light to travel a longer distance within the solar cell. The balls' complex internal structure, meanwhile, creates a surface area of about 1,000 square feet for each gram of material. This internal surface is coated with a dye that captures the light."

"The researchers expected some improvement in the performance but what they saw exceeded their hopes."

"We did not expect the doubling," Cao said. "It was a happy surprise."

"The overall efficiency was 2.4 percent using only small particles, which is the highest efficiency achieved for this material. With the popcorn-ball design, results presented today at the conference show an efficiency of 6.2 percent, more than double the previous performance."

A brief survey of some sites that cover the major advantage and disadvantages of the technology (compared to other solar power generation methods). Briefly the advantages focus on the cost and potential ease of physical application in existing manufacturing vs. the drawbacks of lower efficiency and liquid electrolyte solution.

• Natural Dye-Sensitized Nanocrystalline Solar Cell from University of Toronto


• Wikipedia page


• Nanosense information


• HPCC of NECTEC, Organic Solar Cells


• Quasi-solid-state dye-sensitized solar cells with cyanoacrylate as electrolyte matrix