title: Hot-electron transfer from semiconductor nanocrystals.
abstract: In typical semiconductor solar cells, photons with energies above the semiconductor bandgap generate hot charge carriers that quickly cool before all of their energy can be captured, a process that limits device efficiency. Although fabricating the semiconductor in a nanocrystalline morphology can slow this cooling, the transfer of hot carriers to electron and hole acceptors has not yet been thoroughly demonstrated. We used time-resolved optical second harmonic generation to observe hot-electron transfer from colloidal lead selenide (PbSe) nanocrystals to a titanium dioxide (TiO2) electron acceptor. With appropriate chemical treatment of the nanocrystal surface, this transfer occurred much faster than expected. Moreover, the electric field resulting from sub-50-femtosecond charge separation across the PbSe-TiO2 interface excited coherent vibrations of the TiO2 surface atoms, whose motions could be followed in real time.
authors.affiliation: Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455, USA.
authors.forename: William A
authors.initials: WA
authors.lastname: Tisdale
authors.forename: Kenrick J
authors.initials: KJ
authors.lastname: Williams
authors.forename: Brooke A
authors.initials: BA
authors.lastname: Timp
authors.forename: David J
authors.initials: DJ
authors.lastname: Norris
authors.forename: Eray S
authors.initials: ES
authors.lastname: Aydil
authors.forename: X-Y
authors.initials: XY
authors.lastname: Zhu