We have observed that absorption of a single photon by a semiconductor nanocrystal can produce multiple excitons with up to 100% efficiency depending upon the energy of the photon [Phys. Rev. Lett. 2004, 92, 186601]. Generation of multiexcitons from a single photon, which has been confirmed by several other research groups since our initial demonstration, also begins to occur once the process is energetically possible. This is in contrast to bulk materials, which undergo this process with low efficiency and only for significantly higher photon energies relative to the semiconductor band gap. We monitor multiexciton generation as a function of absorbed photon energy and observe that multiexcitons are produced on an ultrafast timescale following the photon absorption event. This effect is particularly attractive as a means of increasing solar cell power conversion efficiency via an increase in photocurrent for photon absorption at the blue end of the solar spectrum and has been cited as a possible operation mechanism for low-cost, high-efficiency Generation III solar cells.