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      Stacking in colloidal nanoplatelets: tuning excitonic properties

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      Author(s)
      Guzelturk, B.
      Erdem, O.
      Olutas M.
      Kelestemur Y.
      Demir, Hilmi Volkan
      Date
      2014
      Source Title
      ACS nano
      Print ISSN
      1936-0851
      Electronic ISSN
      1936-086X
      Publisher
      American Chemical Society
      Volume
      8
      Issue
      12
      Pages
      12524 - 12533
      Language
      English
      Type
      Article
      Item Usage Stats
      202
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      359
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      Abstract
      Colloidal semiconductor quantum wells, also commonly known as nanoplatelets (NPLs), have arisen among the most promising materials for light generation and harvesting applications. Recently, NPLs have been found to assemble in stacks. However, their emerging characteristics essential to these applications have not been previously controlled or understood. In this report, we systematically investigate and present excitonic properties of controlled column-like NPL assemblies. Here, by a controlled gradual process, we show that stacking in colloidal quantum wells substantially increases exciton transfer and trapping. As NPLs form into stacks, surprisingly we find an order of magnitude decrease in their photoluminescence quantum yield, while the transient fluorescence decay is considerably accelerated. These observations are corroborated by ultraefficient Forster resonance energy transfer (FRET) in the stacked NPLs, in which exciton migration is estimated to be in the ultralong range (>100 nm). Homo-FRET (i.e., FRET among the same emitters) is found to be ultraefficient, reaching levels as high as 99.9% at room temperature owing to the close-packed collinear orientation of the NPLs along with their large extinction coefficient and small Stokes shift, resulting in a large Forster radius of similar to 13.5 nm. Consequently, the strong and long-range homo-FRET boosts exciton trapping in nonemissive NPLs, acting as exciton sink centers, quenching photoluminescence from the stacked NPLs due to rapid nonradiative recombination of the trapped excitons. The rate-equation-based model, which considers the exciton transfer and the radiative and nonradiative recombination within the stacks, shows an excellent match with the experimental data. These results show the critical significance of stacking control in NPL solids, which exhibit completely different signatures of homo-FRET as compared to that in colloidal nanocrystals due to the absence of inhomogeneous broadening.
      Keywords
      Colloidal quantum wells
      Colloidal nanoplatelets
      Nonradiative energy transfer
      Förster resonance energy transfer
      Time-resolved fluorescence spectroscopy
      Exciton trapping
      Permalink
      http://hdl.handle.net/11693/12549
      Published Version (Please cite this version)
      http://dx.doi.org/10.1021/nn5053734
      Collections
      • Department of Electrical and Electronics Engineering 3863
      • Department of Physics 2484
      • Institute of Materials Science and Nanotechnology (UNAM) 2098
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