Photoexcitation Dynamics in Films of C-60 and Zn Phthalocyanine with a Layered Nanostructure

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Lane P. A., Cunningham P. D., Melinger J. S., Kushto G. P., Esenturk O., Heilweil E. J.

PHYSICAL REVIEW LETTERS, vol.108, no.7, 2012 (SCI-Expanded) identifier identifier identifier

  • Publication Type: Article / Article
  • Volume: 108 Issue: 7
  • Publication Date: 2012
  • Doi Number: 10.1103/physrevlett.108.077402
  • Journal Name: PHYSICAL REVIEW LETTERS
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Middle East Technical University Affiliated: Yes

Abstract

We elucidate photoexcitation dynamics in C-60 and zinc phthalocyanine (ZnPc) from picoseconds to milliseconds by transient absorption and time-resolved terahertz spectroscopy. Autoionization of C-60 is a precursor to photocarrier generation. Decay of the terahertz signal is due to decreasing photocarrier mobility over the first 20 ps and thereafter reflects recombination dynamics. Singlet diffusion rates in C-60 are determined by modeling the rise of ground state bleaching of ZnPc absorption following C-60 excitation. Recombination dynamics transform from bimolecular to monomolecular as the layer thickness is reduced, revealing a metastable exciplex at the C-60/ZnPc interface with a lifetime of 150 mu s.