Homemade solar cells require the following materials. A copper sheet, a clear Plexiglass sheet, a thin wood strip, emery cloth, some copper wire, some duct tape, table salt, a metal guillotine, a band saw and an electric hotplate. To begin with cut out a 6×6 inch square of copper sheet with the help of your metal guillotine, otherwise a tin snip should work.
Now wash the copper sheet and your hands of all the grease and other contaminants well, and dry both well. Take a piece of emery cloth and polish both sides of the copper plate off the oxide and other tarnish until the bright and clean copper shines through. Then to make your homemade solar cells, place this copper plate on the electric hob and turn it up to the maximum power.
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Well, didn’t we just remove all the oxide off the plate and now we are heating it to make more oxide? Yes, we will heat it to make cuprous oxide, which is a black color oxide of copper formed when it is heated at a high temperature. Now that you have placed the copper sheet on top of the hob you will see that various patina begin to appear on the plate like oranges, purples which glide and change shapes like live things on the copper plate.
Enjoy this show for a while and also if you are doing this in a lab then get some nitric acid and remove the cupric oxide layer by washing or swabbing with it. After half an hour to 45 minutes you will see a black crusty layer beginning to form on the copper plate: a precursor to your homemade solar cells! You will see a few more color changes underneath and it will continue to heat.
This black layer will have thickened further, now it is time to switch off the hob. Let it cool for half an hour. As the copper plate cools it shrinks, and the cuprous oxide layer crackles and begins to separate from the plate.
Knock the side of this plate on a hard surface and you will see the crackled cuprous oxide fall to the surface. Now put this plate under running water and rub gently with your finger, let whatever washes off flow away and let what remains on the plate be there as the plate beneath has become thinner and fragile. Beneath this layer of black cuprous oxide is a reddish orange layer of copper which is photosensitive.
This is what works as an electrode for your homemade solar cells. The wooden strip is used to make a spacer; using duct tape is best as it is made of plastic which is a bad conductor of electricity. The other electrode should not touch our oxidized copper plate and allow the sunlight to fall on it.
The thick copper wire serves as the second electrode, but if you like you can even use the remaining piece of the copper plate too. The electrolyte used is salt water which conducts electricity from one electrode to the other. Cover this arrangement with a plexiglass lid and connect the wires of the electrodes into a voltmeter and place in the sun. You will see the voltmeter needle jump to 20 to 40 volts as your homemade solar cells come alive!
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