Make Solar Cells
Solar cells convert the sun's energy into electricity, similar to the way plants convert the sun's energy into food through photosynthesis. Solar cells work by using the sun's energy to enable electrons in semiconducting materials to move from orbits close to the nuclei of their atoms to higher orbits where they can conduct electricity. Commercial solar cells use silicon as the semiconductor, but here is a way to make a solar cell with more accessible materials to see for yourself how it works.
Contents
Steps
Coating the Glass Plates
- Obtain 2 equal-sized glass plates. Plates of the size used as covers for microscope slides would be ideal.
- Clean both surfaces of the plates with alcohol. Once the plates are cleaned, handle them only by the edges.
- Test the plate faces for conductivity. Do this by touching the surfaces with the leads from a multimeter. Once you have established which side of each plate is the conductive side, place them side by side, one plate conductive side up and the other conductive side down.
- Apply transparent tape to the plates. This will hold the plates in place for the next step.
- Place the tape along either of the long side of the plates to overlap 1 millimeter (1/25 inch) of the edges.
- Place tape over the outer 4 to 5 millimeters (1/5 inch) of the conductive side up plate.
- Apply a solution of titanium dioxide to the plates. Put 2 drops on the conductive side up plate, then spread it evenly over the plate surface. Allow the titanium dioxide to cover the conductive-side-down plate.
- Before applying the titanium dioxide solution, you may first want to coat the plates with tin oxide.
- Remove the tape and separate the plates. Now you'll treat the 2 plates differently.
- Place the conductive-side-up plate on an electric hot plate overnight to bake the titanium dioxide onto the plate.
- Clean the titanium dioxide off the conductive-side-down plate and place it where it won't collect dirt.
- Prepare a shallow dish filled with dye. The dye can be made from raspberry, blackberry or pomegranate juice or by brewing a tea from red hibiscus petals.
- Soak the titanium-dioxide-coated plate, coated side down, in the dye for 10 minutes.
- Clean the other plate with alcohol. Do this while the titanium dioxide-coated plate is soaking.
- Retest the cleaned plate to find its conductive side. Mark the side that doesn't conduct with a plus sign (+).
- Apply a thin carbon coating to the conductive side of the cleaned plate. You can do this by going over the conductive side with a pencil or by applying a graphite lubricant. Cover the entire surface.
- Take the titanium-dioxide-coated plate out of the dye. Rinse it twice, first with de-ionized water and then with alcohol. Blot dry after rinsing with a clean tissue.
Assembling the Solar Cell
- Place the carbon-coated plate onto the titanium-dioxide plate so the coatings touch. The plates should be slightly offset, about 5 millimeters (1/5 inch). Use binder clips on the long edges to hold them in place.
- Apply 2 drops of an iodide solution to the exposed coating. Let the solution soak through the plate coatings so they're covered completely. You may want to open the binder clips and gently lift 1 of the plates up to allow the solution to spread over the entire surface.
- The iodide solution will enable electrons to flow from the titanium-dioxide-coated plate to the carbon-coated plate when the cell is exposed to a light source. Such a solution is called an electrolyte.
- Wipe excess solution off the exposed portions of the plates.
Activating and Testing the Solar Cell
- Attach an alligator clip to the exposed coated sections on either side of the solar cell.
- Connect the black wire of the multimeter to the clip connected to the exposed titanium dioxide coating. This plate is the solar cell's negative electrode, or cathode.
- Connect the red wire of the multimeter to the clip connected to the exposed carbon coating. This plate is the solar cell's positive electrode, or anode. (In a previous step, you marked it with a plus sign on its non-conductive side.)
- Place the solar cell next to a light source, with the negative electrode facing the source. In a school classroom, this can be done by laying the cell on top of the lens of an overhead projector. In a home setting, another light source, such as a spotlight or the sun itself, can be substituted.
- Measure the current and voltage generated by the solar cell with the multimeter. Do this both before and after the cell is exposed to light.
Tips
- You can also make a solar cell by using 2 small sheets of brushed copper and setting 1 of them on the hot plate for half an hour until the copper turns black. Let it cool and remove the black cupric oxide coating, but leave the red cuprous oxide coating beneath it to serve as your semiconductor. You won't need to coat the copper sheet with anything, and you'll use a salt water solution as your electrolyte.
Warnings
- Neither the coated glass plate nor the copper sheet semiconductor solar cells produce a large amount of power by themselves. Silicon is used in semiconductors because it is more efficient than either of the materials used in this article; however, individual silicon solar cells are assembled into solar panels.
Things You'll Need
- Glass plates (such as microscope slide covers)
- Alcohol (ethanol recommended)
- De-ionized water
- Voltmeter/multimeter
- Transparent tape
- Petri dish or other shallow dish
- Electric hot plate (1100 watts, if possible)
- Titanium dioxide solution
- Tin oxide solution (optional)
- Carbon graphite pencil or lubricant stick
- Iodide solution
- Binder clips
- Alligator clips
