Indium is only used for the clear ITO electrode, though. So if scarcity of Indium were the only concern, then only the "front" carbon electrode would be releva

Indium is only used for the clear ITO electrode, though. So if scarcity of Indium were the only concern, then only the "front" carbon electrode would be relevant--the rest of the photovoltaic structure could be anything you wanted (including Si).