Cut two identical sheets of copper with the shears. They should be as large as possible and still able to fit on the stove's largest burner. Wash one of the copper sheets thoroughly with soap and water. Sand it to ensure the surface is completely clean.
Turn the largest burner on the stove to its highest setting and place the clean copper sheet on it. Heat the copper sheet until it turns black, and continue heating it for an additional half hour.
Turn the burner off but keep the copper sheet on it. Allow the sheet to cool for about 20 minutes and scrub it gently to remove most of the black layer. Be careful not to remove the red layer as it provides the photoelectric effect you will need.
Cut the top of the plastic bottle so that it forms an open cylinder. Place both sheets of copper inside the bottle so that the red layer you created in Step 3 faces towards the outside. Shape the sheets so that they fit the curvature of the bottle and position them so they don't touch each other. Connect the alligator clips to the leads on the ammeter. Clip the negative terminal to the copper sheet with the red layer, and clip the positive lead to the clean copper sheet.
Mix 2 tablespoons of salt into a half gallon of hot tap water and pour the salt water into the bottle until only the top inch of the plates is above the water. Place the bottle in full sunlight and monitor the current that your photovoltaic cell produces with the ammeter.