title: Photoluminescence Blinking and Reversible Electron Trapping in Copper-Doped CdSe Nanocrystals.
abstract: Single-particle photoluminescence blinking is observed in the copper-centered deep-trap luminescence of copper-doped CdSe (Cu(+):CdSe) nanocrystals. Blinking dynamics for Cu(+):CdSe and undoped CdSe nanocrystals are analyzed to identify the effect of Cu(+), which selectively traps photogenerated holes. Analysis of the blinking data reveals that the Cu(+):CdSe and CdSe nanocrystal "off"-state dynamics are statistically identical, but the Cu(+):CdSe nanocrystal "on" state is shorter lived. Additionally, a new and pronounced temperature-dependent delayed luminescence is observed in the Cu(+):CdSe nanocrystals that persists long beyond the radiative lifetime of the luminescent excited state. This delayed luminescence is analogous to the well-known donor-acceptor pair luminescence of bulk copper-doped phosphors and is interpreted as revealing metastable charge-separated excited states formed by reversible electron trapping at the nanocrystal surfaces. A mechanistic link between this delayed luminescence and the luminescence blinking is proposed. Collectively, these data suggest that electron (rather than hole) trapping/detrapping is responsible for photoluminescence intermittency in these nanocrystals.
authors.affiliation: Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, United States.
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Whitham
authors.affiliation: Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, United States.
authors.forename: Kathryn E
authors.initials: KE
authors.lastname: Knowles
authors.affiliation: Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, United States.
authors.forename: Philip J
authors.initials: PJ
authors.lastname: Reid
authors.affiliation: Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, United States.
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Gamelin
keywords: Doped nanocrystal; blinking; carrier trapping; copper dopant; delayed luminescence; luminescence intermittency