A metallic molybdenum suboxide buffer layer for organic electronic devices

Molybdenum trioxide (MoO3) is commonly used as a buffer layer in organic electronic devices to improve hole-injection. However, stoichiometric MoO3 is an insulator, and adds a series resistance. Here it is shown that a MoO3 buffer layer can be reduced to form a metallic oxide buffer that exhibits more favorable energy-level alignment with N,N'-diphenyl-N,N'-bis-(1-naphthyl)-1-1'-biphenyl-4,4'-diamine (alpha-NPD) than does MoO3. This buffer layer thus provides the conductivity of a metal with the favorable energy alignment of an oxide. Photoemission shows the reduced oxide contains Mo4+ and Mo5+, with a metallic valence band structure similar to MoO2. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3432447]