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Title: The impact of inverse photoemission spectroscopy measurements on regioregular poly(3-hexylthiophene) films

Inverse photoemission spectroscopy (IPES) enables the characterization of the density of states of unoccupied energy states above the Fermi level. However, due to the relatively high electron currents required to achieve useful signal to noise ratios, sample damage is a concern. Regioregular poly(3-hexylthiophene) (rr-P3HT) was used to systematically study the influence of electron radiation during IPES measurements on a prototypical conductive polymer. A series of IPES measurements exposing the samples to a range of electron fluxes was performed. An analysis of the electronic structure and the morphology showed that significant changes occurred in the investigated samples depending on the electron flux. X-ray diffraction results revealed that the root cause of the spectral changes is most likely related to crystallization of the film in an edge-on orientation. This was confirmed by Raman spectroscopy where both the C-C and C=C stretch modes shifted to lower frequencies after 5 IPES scans indicating a more ordered molecular structure. The observation of these stretch modes even after exposure to higher electron flux indicates that the main chemical structure of the P3HT molecules remains mostly intact during the IPES measurements. The absence of significant changes in C 1s and S 2p photoemission core level lines alsomore » confirmed this conclusion.« less
Authors:
;  [1] ; ;  [2]
  1. Department of Electrical Engineering, University of South Florida, Tampa, Florida 33620 (United States)
  2. Department of Chemistry, University of South Florida, Tampa, Florida 33620 (United States)
Publication Date:
OSTI Identifier:
22275720
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 104; Journal Issue: 2; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; CRYSTALLIZATION; ELECTRONIC STRUCTURE; FERMI LEVEL; PHOTOEMISSION; RAMAN SPECTROSCOPY; SIGNAL-TO-NOISE RATIO; THIN FILMS; X-RAY DIFFRACTION