An unexpected discovery working with LEDs may help in making more efficient, low cost solar cells. Researchers at Lawrence Berkeley National Labs were working with a new generation of wide-band gap LEDs which shine blue instead of the more traditional red when they ran across something strange. They were trying to get LEDs to work with indium nitride, but they couldn't get them to shine at the published band gap of 2 eV. After some further research they found the band gap was actually much lower, 0.7 eV to be exact. Because of this discovery, indium nitride nicely fills a gap which could allow for a full spectrum solar cell and allow for a theoretical 50% maximum efficiency in a two layer cell. Currently, the most efficient two layer solar cell is 30%.
Indium gallium nitride's advantages are many. It has tremendous heat capacity and, like other group III nitrides, is extremely resist to radiation. These properties are ideal for the solar arrays that power communications satellites and other spacecraft. But what about cost?
"If it works, the cost should be on the same order of magnitude as traffic lights," Walukiewicz says. "Maybe less." Solar cells so efficient and so relatively cheap could revolutionize the use of solar power not just in space but on Earth.
There are some problems that need to be overcome since indium gallium nitride crystals are "riddled with defects." But research in LEDs has shown the material is quite defect-tolerant, and the group hopes2