The solar industry is healthy and thriving! Just as traditional polycrystalline photovoltaics (PV) begin to take root in American homes, a plethora of new solar ideas flood research labs. Scientists around the world have been working tirelessly to increase the efficiency of, and integrate new materials into, photovoltaic solar cells. Some interesting products have come to fruit: multi-junction concentrators, thin-film solar cells, Power Plastic, and the topic of this article: dye-sensitized solar cells.
It’s one thing to produce electricity from pretty pre-manufactured solar panels out-of-the box, but here at andthenBAM.com we like to get our hands dirty! This, due to the manufacturing process, just hasn’t been possible with conventional mono- poly- crystalline solar cells. We can, however, build our own dye-sensitized solar cells! Some of the materials, unfortunately, are somewhat special and may only be ordered from specific labs, while others are simple enough to be grown in the backyard. More importantly, production does not require special machinery or expertise and may be duplicated in schools and at home. First a brief explanation, then we’ll discuss how to do this ourselves.
Brief Explanation: We start with two glass plates acting as our electrodes. This is special glass with a Transparent Conductive Oxide (TCO) coating to make the glass electrically conductive. The Cathode ( - ) will be coated with a platinum catalyst, and the Anode ( + ) with a Titanium Nano-Oxide paste. This paste does not readily absorb sunlight, so we dye it red according to the desired absorption wavelength. We then put the two electrodes together and seal. Last, we insert electrolyte between the electrodes to allow electron flow and eliminate degradation from “carbon poisoning” from air in potential gaps.
Materials: My colleague, Roma Koulikov, was kind enough to list the materials used in the video on his blog. Please visit http://www.romakoulikov.com/berry-powered-solar-cells/ for a complete list of the materials, prices, and even some tips to avoid our mistakes! Also, I offer the Solaronix do-it-yourself catalog as additional source for reference ~> http://www.solaronix.com/documents/dye_solar_cells_for_real.pdf
First, we need to do some preparation. We will need to drill into one side of our solar cell to later insert electrolyte. Take one glass plate, whichever is destined for the platinum catalyst, and drill two small holes through opposing sides of the TCO glass plate.`
Next, tape your electrodes to a work-surface conductive side up. This tape will act as a guide for applying both the TiO2 paste and the platinum catalyst. You may adjust parameter and thickness of paste through adjustments made to tape placement. Leave sufficient spacing to fit a proper seal, a step a bit later in the process.
IMPORTANT! Mix titanium nan-oxide thoroughly. Using a glass stir rod, apply a thin layer of paste to your electrode. This layer needs to be thin and as smooth as possible. Too much paste / inconsistencies will cause it to crack and flake off during the firing process. Repeat process for platinum catalyst.
Fire both electrodes at 450 degrees Celsius for 10 – 15 minutes. A non-toxic gas may form as titanium bakes to the TCO glass plate. I used a kiln at my local community college for this. After sufficient cooling, scrape the titanium layer away from the edges of the glass to provide spacing for a proper seal later in the process. The fired platinum layer should be invisible to near-invisible. To test if the platinum has taken effect, apply a drop of hydrogen peroxide and look for bubbles.
We are now ready to make our dye! For this, crush fresh or frozen red fruit or berries in a lidded container. Envelope titanium electrode into the dye mixture and place lid. Wait a few hours before removing electrode, and clean thoroughly with deionized water. Repeat if dye has not fully absorbed into titanium paste.
It is time to seal our electrodes together. Cut out sealing film to appropriate size, containing the platinum and titanium sections of our cell. Remember to leave spacing for electrical contacts (you must make a seal with your TCO glass plates askew). You may use a soldering iron to secure the corners of the film to the conductive side of the titanium electrode. Now, use a clothing iron (or similar tool) to evenly melt the film as a whole to the glass (see video above). Remove the protective layer from film, then place your electrodes together. Reapply heat to secure electrodes together; too much heat will mess with the tightness of your seal.
Inject electrolyte into solar cell through holes previously drilled. Cut out small squares of aluminum foil, and place over holes. Place sealing film over aluminum squares, and apply heat.
Bust out your multi-meter and begin testing! In full sunlight, I received an average of .5 volts for the various 10cm x 10cm cells I made.