Organic semiconductor heterointerfaces containing bathocuproine

The four organic–organic heterointerfaces formed by depositing the organic semiconductor bathocuproine on tris(8-hydroxy-quinoline)aluminum $(Alq3),$ $N,N′-diphenyl-N,N′-bis(1-naphthyl)-1,1′$ $biphenyl-4,4″$ diamine (α-NPD), $4,4′-N,N′-dicarbazolyl-biphenyl$ (CBP), and copper phthalocyanine (CuPc) have been studied using ultraviolet photoelectron spectroscopy. The relative positions of the vacuum levels and highest occupied molecular orbital levels 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 interfaces.