27 February 2002 Hole injection energetics at highly conducting polymer anode: small molecule interfaces studied with photoemission spectroscopy
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Abstract
We report a photoemission study of the interfaces between spin-cast films of a new variation of a polymer blend consisting of poly(3,4-ethylenedioxy-thiophene) (PEDOT) and poly(4-styrenesulfonate) (PSS) and glycerol as an additive, and vacuum-evaporated hole transport layers (HTL) of 4,4'-bis(carbazol-9-yl)biphenyl (CBP),N,N'-diphenyl-N,N'-bis(1-naphthyl)-1-1'biphenyl-4,4'di amine (NPD) and N,N'-diphenyl-N,N'-bis(3methylphenyl)-1,1'-biphenyl-4,4'-dia mine (TPD). The hole injection barrier, as deduced from photoemission spectroscopy, is 0.5 - 0.9 eV at the PEDOT-PSS / HTL interface, which compares very well with the previously reported barrier heights for oxygen plasma -treated indium-tin oxide (ITO)/NPD and ITO/TPD interfaces, and which is, most notably, a factor of two smaller than barriers measured for a PEDOT-PSS/hole-transporting luminescent polymer, e.g. poly(bis-(2-dimethyloctylsilyl)-1,4-phenylvinylene, interface. The measured energy barriers imply a sufficiently efficient charge injection at the studied PEDOT-PSS/HTL interface, which is very encouraging for further development of anode structures based on similar conducting polymer blends and chemically modified structures to be utilized in molecular organic light-emitting device applications.
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Antti Johannes Maekinen, Antti Johannes Maekinen, W. H. Kim, W. H. Kim, Ian G. Hill, Ian G. Hill, Ranganathan Shashidhar, Ranganathan Shashidhar, Nikolay Nikolov, Nikolay Nikolov, Zakya H. Kafafi, Zakya H. Kafafi, } "Hole injection energetics at highly conducting polymer anode: small molecule interfaces studied with photoemission spectroscopy", Proc. SPIE 4464, Organic Light-Emitting Materials and Devices V, (27 February 2002); doi: 10.1117/12.457473; https://doi.org/10.1117/12.457473
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