Last week I talked about new advances that allow us to make silicon solar cells more cheaply (see also this primer post on solar to catch up). But the future of light capture may not be constrained to silicon. New technologies are here that may render moot the worldwide shortage of solar-grade polycrystalline silicon.

One of the big new materials that could replace silicon in solar cells is copper indium gallium selenide, or CIGS. The upshot of solar panels made from CIGS cells is that they’d be cheaper and lighter to make than their silicon-based counterparts. As with amorphous silicon (a-Si), CIGS cells are currently less efficient than commercial monocrystalline (c-Si) silicon, but the cost per watt is cheaper — CIGS cells are projected to cost $2.50 per watt in 2010 when manufacturing capacity scales up, compared to c-Si’s current $8-$9 per watt.

Another advantage of CIGS technology is that it’s sprayed onto substrates. This means that it can be made in thin sheets to be incorporated into roof tiles, or even theoretically sprayed onto concrete. CIGS technology hasn’t come close to replacing silicon, but as a disruptive technology, its day may come. (You can read more on the debate at C|Net).

So, can we call these new solar advances “clean technologies”? They certainly produce clean energy; and as their own production gets cleaner, they are adhering to the Cleantech principles. But look around — Nature uses silicon to play on the beach (sand is silicon dioxide), not to capture sunlight; and mostly avoids exotic metals altogether. So what can biomimicry teach us about truly Cleantech solar technology? I’ll discuss these “natural” solar applications of the future next week.

Disclosure: At the time of the writing of this post, I have no financial relationships with any of the organizations mentioned, except as explicitly indicated.