The price of photovoltaic hardware has dropped so dramatically in recent years that, according to some projections, a well-sited panel may become competitive with fossil fuels before the decade is out. To reach that point, which comes when panels cost below $2 per Watt, prices will have to continue their steep decline. During our visit to IBM’s Watson research center, we talked to two people who are working on ways to drive the cost downâ€”but they are taking radically different approaches.
The panels that most people are familiar with use silicon as a semiconductor. That has a few advantages, like cheap raw materials and reasonably high efficiency. But manufacturing panels remains expensive, and there aren’t obvious ways of squeezing large gains in efficiency out of standard silicon. So, IBM is looking at materials that don’t involve silicon: thin films and concentrating photovoltaics.
Thin is in
We talked with David Mitzi, who manages the thin film project. These materials currently tend to be less efficient than silicon-based devices, but they have a large advantage: they can be much less expensive to manufacture. One key to this difference is that the boundaries between crystals in thin-film materials don’t pose a barrier to the charge carriers (electrons and holes) generated by incoming light. While high performance silicon cells require a manufacturing technique that produces a single large crystal, it’s possible to use polycrystalline forms of thin film materials.