Influence of ionization energy change on valence band offset in organic p-n junction

摘要

Valence band offsets at [6,6]-phenyl-C_(61)- butyric acid methyl ester (PCBM)/metallophthalocyanine (MPc, M = Cu and Zn) interfaces have been investigated with ultraviolet photoelectron spectroscopy, which are organic p-n junctions in organic photovoltaics. The highest occupied molecular orbitals of MPcs rise toward the interface, while that of PCBM lowers. This behavior implies that the different energy band offsets from inorganic p-n junction are realized in organic p-n junction. The depletion layers were not observed at the interfaces. Such anomalous energy band offsets are attributed to the interfacial dipole and also ionization energy changes of MPcs and PCBM at the interface.