Semiconductor nanocrystals
DOI: 10.1063/1.4796571
Can provide highly efficient carrier multiplication, which could lead to greatly improved solar cells. Usually, an incident photon striking a semiconductor solar cell produces both an exciton (an electron-hole pair), which generates the usable electrical current, and some excess heat. By using tiny (smaller than 10 nm) clusters of lead and selenium atoms, Victor Klimov and Richard Schaller of Los Alamos National Laboratory encouraged the absorbed photon—via a process known as impact ionization—to spawn a second exciton instead of the heat. Although they haven’t yet built a working solar cell, the scientists say that the new process might provide efficiency gains of more than 35% in the conversion of light to current. (R. D. Schaller, V. I. Klimov, Phys. Rev. Lett. 92, 186601, 2004.http://dx.doi.org/10.1103/PhysRevLett.92.186601 )
