Controlling energy level positions in hole conducting molecular films by additives

Rebecka Lindblad, Johan Oscarsson, Kristofer Fredin, Susanna K. Eriksson, Hans Siegbahn, Erik M.J. Johansson, Håkan Rensmo

Research output: Contribution to journalArticlepeer-review

2 Citations (SciVal)

Abstract

Hard X-ray photoelectron spectroscopy (HAXPES) has been used to study the bulk electronic structure of thin molecular films of the organic compounds 2,2′,7,7′-tetrakis (N,N’-di-p-methoxyphenyl-amine)-9,9’-spiro-bifluorene (spiro-OMeTAD), 4-(diethylamino)-benzaldehyde-1,1)-diphenyl-hydrazone (DEH) and poly(3-hexylthiophene) (P3HT). Molecular layers of these compounds are hole conducting, a property that for example has been used in different solar cell configurations. The function of such a device benefits from the inclusion of additives such as Li-TFSI, or dopants such as Co-complexes, into the molecular layer. Here we report on effects of adding Li-TFSI to DEH and P3HT as observed by photoelectron spectroscopy and we compare with results on the spiro-OMeTAD hole conductor. It can be concluded that the Li-salt causes a shift of the Fermi level in DEH and P3HT towards the HOMO resulting in a p-doping of the molecular material. Similar shifts of the Fermi level could also be observed when adding different Co(+III) complexes to the Spiro-OMeTAD hole conductor, indicating means for more controlled doping.

Original languageEnglish
Pages (from-to)100-106
Number of pages7
JournalJournal of Electron Spectroscopy and Related Phenomena
Volume224
DOIs
Publication statusPublished - 2018 Apr 1

Subject classification (UKÄ)

  • Inorganic Chemistry
  • Condensed Matter Physics

Keywords

  • HAXPES
  • Mesoscopic solar cells
  • P3HT
  • Spiro-OMeTAD

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