Step Forward in Solar Cell Efficiency
- Friday, 11 September 2009
Researchers at Israel's Ben-Gurion University of the Negev have developed thin films that exhibit carrier multiplication (CM) - a development that is of great interest for future solar cells.
“Films developed at BGU show CM, in which each incoming photon (tiny quantity of sunlight) creates more than one electron-hole pair. This can potentially be used for making more efficient solar cells,” explains Yuval Golan, a professor of Materials Engineering. The films were synthesized by Golan and Ph.D. student Anna Osherov.
One of the important factors limiting solar cell efficiency is that incident photons generate only one electron–hole pair, regardless of the photon energy. Any excess photon energy is lost as heat. Carrier multiplication has been thought to be enhanced significantly in nanocrystalline materials such as quantum dots.
The BGU team demonstrated that contrary to this expectation, for a given photon energy, carrier multiplication occurs more efficiently in bulk lead sulfide (PbS) and lead selenide (PbSe) films than in nanocrystalline films of the same materials.
The films were prepared using chemical solution deposition, an inexpensive deposition technique. The research was carried out as part of an international collaboration with researchers in France and the Netherlands.