Controlling energy level positions in hole conducting molecular films by additives

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title = "Controlling energy level positions in hole conducting molecular films by additives",
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.",
keywords = "HAXPES, Mesoscopic solar cells, P3HT, Spiro-OMeTAD",
author = "Rebecka Lindblad and Johan Oscarsson and Kristofer Fredin and Eriksson, {Susanna K.} and Hans Siegbahn and Johansson, {Erik M.J.} and H{\aa}kan Rensmo",
year = "2018",
month = "4",
day = "1",
doi = "10.1016/j.elspec.2017.03.009",
language = "English",
volume = "224",
pages = "100--106",
journal = "Journal of Electron Spectroscopy and Related Phenomena",
issn = "0368-2048",
publisher = "Elsevier",