title: Ultrafast electron trapping in ligand-exchanged quantum dot assemblies.
abstract: We use time-integrated and time-resolved photoluminescence and absorption to characterize the low-temperature optical properties of CdSe quantum dot solids after exchanging native aliphatic ligands for thiocyanate and subsequent thermal annealing. In contrast to trends established at room temperature, our data show that at low temperature the band-edge absorptive bleach is dominated by 1S3/2h hole occupation in the quantum dot interior. We find that our ligand treatments, which bring enhanced interparticle coupling, lead to faster surface state electron trapping, a greater proportion of surface-related photoluminescence, and decreased band-edge photoluminescence lifetimes.
authors: Department of Physics and Astronomy, ⊥Department of Electrical and Systems Engineering, ‡Department of Materials Science and Engineering, and §Department of Chemistry, University of Pennsylvania , Philadelphia, Pennsylvania 19104, United States.
authors: Michael E
authors: ME
authors: Turk
authors: Patrick M
authors: PM
authors: Vora
authors: Aaron T
authors: AT
authors: Fafarman
authors: Benjamin T
authors: BT
authors: Diroll
authors: Christopher B
authors: CB
authors: Murray
authors: Cherie R
authors: CR
authors: Kagan
authors: James M
authors: JM
authors: Kikkawa
keywords: cadmium selenide; electron trapping; ligand exchange; quantum dots; time-resolved absorption; ultrafast fluorescence