Metal oxide induced charge transfer doping and band alignment of graphene electrodes for efficient organic light emitting diodes

Jens Meyer, Piran R. Kidambi, Bernhard C. Bayer, Christ Weijtens, Anton Kuhn, Alba Centeno, Amaia Pesquera, Amaia Zurutuza, John Robertson, Stephan Hofmann

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Abstract

The interface structure of graphene with thermally evaporated metal oxide layers, in particular molybdenum trioxide (MoO3), is studied combining photoemission spectroscopy, sheet resistance measurements and organic light emitting diode (OLED) characterization. Thin (<5 nm) MoO3 layers give rise to an 1.9 eV large interface dipole and a downwards bending of the MoO3 conduction band towards the Fermi level of graphene, leading to a near ideal alignment of the transport levels. The surface charge transfer manifests itself also as strong and stable p-type doping of the graphene layers, with the Fermi level downshifted by 0.25 eV and sheet resistance values consistently below 50 Ω/sq for few-layer graphene films. The combination of stable doping and highly efficient charge extraction/injection allows the demonstration of simplified graphene-based OLED device stacks with efficiencies exceeding those of standard ITO reference devices.
Original languageEnglish
Article number5380
Number of pages7
JournalScientific Reports
Volume4
DOIs
Publication statusPublished - 20 Jun 2014
Externally publishedYes

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