title: Ultrafast exciton dynamics in Type II ZnTe-ZnSe colloidal quantum dots.
abstract: Ultrafast transient absorption spectroscopy is used to investigate the exciton dynamics of Type II ZnTe-ZnSe core-shell colloidal quantum dots. Surface-trapping is shown to occur within a few picosecond for hot electrons and with a few 10s of picoseconds for electrons cooled to the band-edge, and is the dominant process in the decay of the band-edge bleach for well-stirred samples pumped at moderate powers. The surface-trapped electrons produce a broad photo-induced absorption that spectrally overlaps with the band-edge, distorting and partially cancelling out the bleach feature. At high pump powers and for unstirred samples, these surface-trapped electrons can survive sufficiently long within the pumped volume to accumulate under repeated excitation of the sample, resulting in the formation of an additional exciton decay channel.
authors.affiliation: School of Physics and Astronomy & Photon Science Institute, University of Manchester, Manchester, UK.
authors.forename: M
authors.initials: M
authors.lastname: Cadirci
authors.forename: S K
authors.initials: SK
authors.lastname: Stubbs
authors.forename: S M
authors.initials: SM
authors.lastname: Fairclough
authors.forename: E J
authors.initials: EJ
authors.lastname: Tyrrell
authors.forename: A A R
authors.initials: AA
authors.lastname: Watt
authors.forename: J M
authors.initials: JM
authors.lastname: Smith
authors.forename: D J
authors.initials: DJ
authors.lastname: Binks