Cuprous Oxide Solar Cell
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Overview
When copper metal is oxidized it can take several oxidation states.
Cupric oxide with a copper(II) oxidation state is black: 2 Cu + O2 → 2 CuO
cuprous oxide is with the copper(I) oxidation state is red.
- 4 Cu + O2 → 2 Cu2O.
Cuprous oxide is a semiconductor. It has a bandgap between it ground state and its conduction band. Without light some electrons are able to jump the band and it acts as a battery. With light the cuprous oxide jumps to the conduction band and increased electricity flows. In this design the charge moves through a gelatin electroylte and to a non oxidized collection electrode. Using a gelatin electrolyte is less messy that a purely liquid electrolyte. A solid clear conductor is not great for this application because it can not make uniform contact with the copper surface.
Materials
- Copper foil (snail tape) from the gardening store
- Wires and solder
- Clear rigid plastic sheet (old cd case, or plastic lid from salad container.)
- clear plastic packing tape
- clear gelatin
- table salt
- volt meter
Construction
Cut a 2" x 1" strip of the copper foil and remove the adhesive back. Place the foil sticky side up on an stove element under a stove hood fan. When the adhesive burns off a nasty black smoke is produced be sure to do this step with ventilation or out of doors. Turn the burner to high and watch as the copper foil turns from metallic to red to black. Let is cook for 10 minutes to build up a layer of oxide. The black oxide is necessary to create a protective layer that lets only a little oxygen reach the metal surface so it achieves the copper(1) oxidation state.