Hamburg 2001 – scientific programme

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SYOF: Organische Festkörper

SYOF 5: Poster Session

SYOF 5.23: Poster

Tuesday, March 27, 2001, 17:00–19:00, Aula S3

Conjugated Polymers: Hole-Injecting Materials with Adjustable Work Function — •Holger Frohne, Markus Gross, David Mueller, and Klaus Meerholz — Physical Chemistry Dept., University of Munich, Butenandtstr. 11, 81377 Munich

Doped conjugated polymer layers are commonly used to improve the injection of holes in polymer-based OLED devices. Their positive influence is mainly attributed to the more favorable work function of these injection layers compared with ITO. We have recently demonstrated that the exact doping level of the injection layer is of paramount importance for the performance of the devices [Nature 405, 661 (2000)]. By increasing the doping level of such polymers the hole-injection barrier can be continuously reduced, ultimately allowing formation of ohmic contacts with arbitrary hole conductors. We apply this new concept for the detailed characterization of various hole conductors under space-charge-limited current (SCLC) conditions and in OLED devices based on PPV- and polyfluorene (PF) derivatives. The use of combinatorial devices allows to quickly screen for the optimum doping level with reduced operating voltage, improved light output, and highest efficiency.