Thickness effect on photoconduction spectra in solid films of C60

Steady-state photoconductivity action spectra in the wavelength range between 200 and 800 nm have been measured in C60 formed vacuum evaporated films of different thickness. The photoconduction can be described by the interplay between two charge generation mechanisms: auto-ionization of excited states in the bulk, accompanied by excitonic injection of electrons from the Al cathode. The thickness of the films reduces the negative-to-positive photocurrent ratio in the strongest absorption region.