Solar Cell

From: How to Build a Solar Cell That Really Works by Walt Noon
Published by Lindsay Publications, $4.95

Solar cells can be made out of cuprous oxide. Here is the process briefly:

Use a sheet of copper (.025" thick), It should be in the shape of a circle cut out of a square, with one corner of the square left.

1. Clean the copper sheet very thoroughly, it may be necessary to use nitric acid.
2. Heat the copper red hot. Use a propane torch, and make sure it is heated red all over. Keep the torch on one side of the cell, do not let the flame touch the other side. Keep it red for a 2 min 40 sec. This will cause two types of copper oxide to form on the side away from the flame. Cupric oxide is the black flaky stuff that forms. Under this is pinkish cuprous oxide. Lightly rub the cell with coarse steel wool to remove the cupric oxide. Be sure not to damage the cuprous oxide. If the whole side of the cell is not covered, repeat the process. If it is not covered with cuprous oxide on the edges, just cut off the edges.
3. Cover the side with the cuprous oxide with a silvering solution. (so there is a transparent film covering the oxide). Solder a wire to the back (copper side) and another wire to the front (silvered side). The cell is now done, and will produce electricity when exposed to light.