“Even if we don’t feel their scarcity today, if we pulled out all the indium or silicon out of the ground and used it exclusively for solar power, there would be a severe limit to the amount of solar power we could generate,” says Cyrus Wadia, a researcher at the University of California in Berkeley.
U.S. scientists, along with Swiss-based NLV Solar are searching for a possibility to use pyrite for making efficient solar cells, and replace the expensive silicon with a thinner and cheaper option. “This analysis is truly a blend of semiconductor physics and natural resource economic analysis,” he said.
Pyrite based solar cells are nothing new, since NLV already built an electric car powered by them. The sad fact is that, although they’re cheaper to build, for the moment pyrite solar cells are also being very inefficient, only harvesting 3% of the light falling on them (compared to 35.8%, Sharp’s recent breakthrough). Since the 1980s, the efficiency value hasn’t changed much for pyrite solar cells. The advantage is that pyrite is four to five orders more common than silicon in nature.
Until now, pyrite-based solar cells have been limited to their little performance due to the fact that although the chemical formula is the same, its physical structure, or phase, can vary from one piece to another. Unless the entire cell is the same phase, it can only achieve the 3 percent efficiency that has been reported for over 25 years. Even slight variations dramatically reduce its ability to convert sunlight into electricity.
Wadia thinks he has solved this problem by using nanocrystals. By manipulating pyrite at an atomic level, Wadia can increase the number of wavelengths his pyrite solar cell can capture while also eliminating the trace amounts of out-of-phase pyrite.
For now, however, Wadia’s two prototype solar cells can only convert 1.6 percent of the light that hits them into electricity. The pyrite is all the same phase, but its different sizes. He also didn’t use only pyrite. He had to incorporate cadmium into the solar cell as well, a material he hopes to remove from later iterations.
By using multiple layers, NLV claimed that their newly-modified pyrite solar cells could reach the performance of converting about 50% of the incident light into electricity. If that would happen, pyrite is the new best friend of solar manufacturers, investors, consumers and of the environment. But until such a figure is confirmed, we’ll have to rely on what we already have.