As improbable as it may seem, it’s possible to construct a simple light-wave communication system using a solar cell consisting of two pennies.1,2 This unusual take on a light sensor was inspired by Internet sites showing how copper may be used in solar cell construction.3,4 Since pennies minted before 1982 consist of 95% copper, they are good candidates for solar cell fabrication.

The solar cell described in this article is actually a light-enhanced electrochemical cell. The device consists of two copper electrodes, one of which is a light-sensitive semiconductor, immersed in an electrolyte solution. Chemical reactions occurring at the electrodes are the same as those that occur in a standard electrochemical cell, except that light is explicitly involved in providing energy to cause the reactions to occur.

Heating a penny produces two oxidation states of copper: cupric and cuprous oxide, the latter being a semiconductor.5 A penny...

Supplementary Material

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