Rice University Researchers Give Big Boost To Solar Power
Though great advances have been made to maximize the amount of sunlight that is absorbed by solar cells, the best solution, until now, is a two-step chemical process that enables the cells to absorb 96 percent of the sun's light. That's an excellent result. But Rice University chemists have created a single-step process that enables the cells to absorb 99 percent of the sun's light, a process that is not only more efficient than other current processes, but less expensive.
Solar cells are primarily made of silicon, which, in its natural white state does not absorb light, but reflects it. Chemists have created a variety of coatings to enhance silicon's absorbtion of light, but absorbtion depends on a variety of factors, including the range of light, angle, and wavelength. The process developed by Rice University addresses all three of these factors.
The development team, headed by Andrew Barron and graduate student Yen-Tien Lu, has created a 'chemical stew' of copper nitrate, phosphorous acid, hydrogen flouride and water. As described by a Rice University press release:
"When applied to a silicon wafer, the phosphorous acid reduces the copper ions to copper nanoparticles. The nanoparticles attract electrons from the silicon wafer's surface, oxidizing it and allowing hydrogen flouride to burn inverted pyramid-shaped nanopores into the silicon."
This process, in other words, turns the silicon wafer black and etches the surface of the silicon to create spikes so that light can be absorbed by each facet at various times of the day, from sunrise to sunset, absorbing 99 percent of exposed light.
Barron and Lu will continue refining their silicon blacking and etching process, trying to reduce the time it takes to complete, now eight hours, as well as developing a compound to protect the etched surface of the silicon.