Phthalocyanine/C-60 composites as improved photosensitive materials

We have investigated the influence of C-60-fullerenes as a dopant in thin l ayers of phthalocyanines (Pc). We expect that C-60 acts as an electron acce ptor. Charge transfer of an electron from the first excited state of the Pc to C-60 occurs, thus leading to an enhanced number of free holes, which ar e the majority charge carriers in phthalocyanine. The observation of lumine scence in co-evaporated layers of phthalocyanines and C-60 shows a fluoresc ence quenching depending on the amount of fullerenes. This shows that the a dmixture of C-60 reduces direct recombination of electron-hole pairs and th ereby increases the charge-generation efficiency. The effect on photoconduc tivity is established by electro-optical measurements, which show an improv ed current-voltage characteristic of C-60-doped phthalocyanine layers.