Nanosilicon ink is something of a wild card. Manufacturers Kovio, Seiko Epson etc of devices that use it are targeting transistors at present but it has such excellent properties that they expect it to make a good photovoltaic as well, though it is annealed at high temperature and therefore typically deposited reel to reel on stainless steel. It will not be transparent and metal detectors many not like it but its combination of low cost and high efficiency may be formidable.