Substrates for roll-printed solar cells (and roll-to-roll electronics generally) are a challenge in themselves 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 less expensive than stainless steel work with roll-manufactured thin-film solar cells. But it turns out that the process conditions of conventional 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.

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 called a "major breakthrough" by independent industry experts -- as it radically reduces the materials cost of a thin-film solar cell.