In this article, we learn how to build a photochemical solar cell, also called a Gratzel cell, named after the scientist who developed this technology. A photochemical cell mimics nature in the way that plants soak up and absorb ultraviolet light from the sun. The radiated energy is transferred into electrical energy through a chemical process in the solar cell much like photosynthesis. When light strikes the transparent electrode, the dye in the cell is excited and electrons are discharged. Photochemical solar cells are also cheaper to produce than photovoltaic because the titanium dioxide used in this process is readily available in common products like paint and toothpaste.
Things You'll Need
- Alligator clips
- Nanocrystalline titanium dioxide
- Glass rods
- Mortar and pestle
- Petri dishes
- Graphite pencil
- Bunsen burner
- Glass plates
- Ethanol solution
Preparing the Titanium Dioxide Suspension
Titanium dioxide can be found in common items like whitening toothpaste and titanium white paint. To make this type of solar cell, grind the titanium dioxide into small particles using a mortar and pestle.
Next, coat the powdered suspension onto a glass plate. You can easily spread the powder by using a small glass rod. Be sure to get an even coverage of titanium dioxide to boost the reaction rate.
Reduce the resistivity of the titanium dioxide by sintering it. The most conventional method of heating the plate to approximately 450 degrees Celsius (842 Fahrenheit) is to sinter it over the tip of a Bunsen flame. A steady exposure of fifteen minutes is enough to allow the titanium dioxide particles to adhere into a film.
Berries and Electrons
To sensitize the solar cell, first crush up a handful of berries. Use the mortar and pestle to produce a deep red or purple fluid. You can use blackberries, raspberries, strawberries, or even pomegranate seeds to make the dye.
Take the electrode which has been coated in the titanium dioxide film and spread the berry fluid onto it. Make sure the dye is evenly spread.
Once you have stained the plate, wash it with an ethanol solution and blot to dry.
Next, take an eyedropper and apply a few drops of iodine onto the plate.
The Second Electrode
Take another coated glass plate and a graphite pencil. Find the conductive side of the plate by rubbing your fingers along the surface. The side that has a rougher surface is the conductive side. Use the soft lead pencil to scribble on a coating of graphite to the conductive side.
Place this electrode on top of the dyed electrode. Stagger the two plates so that some surface area shows on each one.
Finally, attach the two plates together using gator clips. Now you have made a fully operational photochemical solar cell.
Tips & Warnings
- You can use a multimeter to measure and record the amount of power your solar cell is harnessing.
- As a safety precaution, be sure to use protective gloves and a respirator mask.
- Photo Credit Image Courtesy of NIMS NOW (c) 2008
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