Substrates for roll-printed solar cells (and roll-to-roll electronics generally) are a challenge due to the many constraints that they need to fulfill: They need to be highly smooth, sufficiently flexible to enable roll-to-roll processing, compatible with all process conditions of each process step (ranging from temperature to the device layering and the cell-interconnect technology chosen), and fulfill many other constraints.

Many groups around the world have tried to make substrates work for CIGS which are less expensive than stainless steel. But it turns out that the process conditions of vacuum processes (including the temperature required) are tough on substrates, and so despite their high cost, stainless-steel substrates are generally used for vacuum-deposited thin-film solar cells.   To wit, inexpensive substrates traditionally are not resilient enough for CIGS production.

Nanosolar has been able to exploit its printing process technology to enable thin-film solar cells on substrates that are an entire order of magnitude less expensive than stainless steel.  This alone was identified a "major breakthrough" by independent industry experts -- as it cuts in half the fundamental materials cost of an entire thin-film solar cell.