An interlayer Li inserting between copper phthalocyanine (CuPc) and Al improves both electric and luminous properties of an organic light-emitting diode (OLED). X-ray photoelectron spectroscopy (XPS) surface analysis technique is employed to investigate chemical binding conditions of CuPc/Li interface. At varying thicknesses of Li deposited on CuPc, we have studied C-1s and Cu-2p XPS of CuPc films. Investigation demonstrates that Cu atoms are liberated from CuPc with increasing Li thicknesses. The results reveal that an OLED with an indium tin oxide glass/triphenyldiamine derivative/tris(8-hydroxyquinoline)aluminum/CuPc/Li/Al structure employing a 2 nm thick Li exhibits optimum performance. It can satisfy commercial demands in not only good reproducibility but also a large area of uniformality. (C) 2003 The Electrochemical Society.