The interfacial electronic structures of N, N′ -bis(1-naphthyl)- N, N′ -diphenyl-1, 1′ -biphenyl-4, 4′ -diamine (NPB)/copper phthalocyanine (CuPc) Au, NPB C60 Au, and NPBCuPc: C60 composite/Au were investigated by in situ ultraviolet photoelectron spectroscopy to understand the highly efficient hole injection in organic light-emitting diode. The hole-injection barrier of CuPc: C60 Au was 0.52 eV, while those of CuPcAu and C60 Au were 0.96 and 1.62 eV, respectively. The lowered injection barrier is attributed to the smaller interface dipole of CuPc: C60 compared to that of pristine CuPc. This small interface dipole pulled up the highest occupied molecular orbital of CuPc in composite, which results in the decreased hole-injection barrier.
Bibliographical noteFunding Information:
This work was supported by the BK21 project of the Korea Research Foundation (KRF) and the KOSEF through National Core Research Center for Nanomedical Technology.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy (miscellaneous)