Phthalocyanine/C60 composites as improved photosensitive materials

Abstract

We have investigated the influence of C₆₀-fullerenes as a dopant in thin layers of phthalocyanines (Pc). We expect that C₆₀ acts as an electron acceptor. Charge transfer of an electron from the first excited state of the Pc to C₆₀ occurs, thus leading to an enhanced number of free holes, which are the majority charge carriers in phthalocyanine. The observation of luminescence in co-evaporated layers of phthalocyanines and C₆₀ shows a fluorescence quenching depending on the amount of fullerenes. This shows that the admixture of C₆₀ reduces direct recombination of electron–hole pairs and thereby increases the charge-generation efficiency. The effect on photoconductivity is established by electro-optical measurements, which show an improved current–voltage characteristic of C₆₀-doped phthalocyanine layers.