Indium Tin Oxide or Graphene in OPV

OPV cells are expected to be much lower efficiency than traditional photovoltaics, but make up for it by being even lower in cost by comparison.

To me it's never seemed like "inexpensive" and "indium" belong in the same sentence.

So off the top of my head I would say graphene which is just fancy carbon rather than a rare element like indium.

I would want to try them both in the lab but if you scale up there's probably not enough indium to go around no matter how thin you spread it.