Organic semiconductor heterointerfaces containing bathocuproine

The four organic-organic heterointerfaces formed by depositing the organic semiconductor bathocuproine on tris(8-hydroxy-quinoline)aluminum (Alq(3)), N,N'-diphenyl-N,N'-bis(1-naphthyl)-1,1' biphenyl-4,4 " diamine (alpha-NPD), 4,4'-N,N'-dicarbazolyl-biphenyl (CBP), and copper phthalocyanine (CuPc) ha ve been studied using ultraviolet photoelectron spectroscopy. The relative positions of the vacuum levels and highest occupied molecular orbital level s of the organics were measured at each interface. Within our experimental uncertainty of 100 meV, the vacuum levels were found to align at all four i nterfaces. (C) 1999 American Institute of Physics. [S0021-8979(99)04520-X].