A frequently voiced concern about solar energy is the dependence of solar cells on rare earth elements such as indium. While rare earth elements are actually far more plentiful than their name suggests, it’s also encouraging to see studies showing that components made from abundant elements can replace them.
In this case, a team headed by Marc C. Hersam at Northwestern has found that they can replace indium tin oxide with carbon nanotubes, one of many examples of extremely versatile carbon replacing other elements that I expect to see in years to come.
From Science Daily:
Solar cells are composed of several layers, including a transparent conductor layer that allows light to pass into the cell and electricity to pass out; for both these actions to occur, the conductor must be both electrically conductive and also optically transparent. Few materials concurrently possess both of these properties.
Currently, indium tin oxide is the dominant material used in transparent conductor applications, but the material has two potential limitations. Indium tin oxide is mechanically brittle, which precludes its use in applications that require mechanical flexibility. In addition, Indium tin oxide relies on the relatively rare element indium, so the projected increased demand for solar cells could push the price of indium to problematically high levels.
Hersam and Marks’ team has created an alternative to indium tin oxide using single-walled carbon nanotubes, tiny, hollow cylinders of carbon just one nanometer in diameter.