The interfacial electronic structures of N,N′-bis(1-naphthyl)-N,N′-diphenyl-1,1′-biphenyl-4,4 ′-diamine (NPB)/hexadecafluoro copper phthalocyanine (F16CuPc)/Au and NPB/copper phthalocyanine (CuPc)/Au were investigated by in situ X-ray and ultraviolet photoelectron spectroscopy to study the hole-injection barrier depending on the ionization energy of hole-injection layer materials. Although the measured ionization energy of F16CuPc (6.30 eV) was much higher than that of CuPc (5.15 eV), the difference in the barrier heights of the two different films was relatively marginal (0.27 eV) due to the formation of interface dipole caused by the charge redistribution. We confirmed that the interface dipole of the buffer layer (CuPc and F16CuPc) pushed down the core levels as well as the valence levels of the top organic layer (NPB) in the NPB/F16CuPc/Au and NPB/CuPc/Au heterojunction.
Bibliographical noteFunding Information:
This work is supported by the BK21 project of the Korea Research Foundation (KRF), and the KOSEF through the National Core Research Center for Nanomedical Technology.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Mechanics of Materials
- Mechanical Engineering
- Metals and Alloys
- Materials Chemistry