Effects of oxygen on the photocarrier dynamics in C/sub 60/ film: studies of photoconductivity and photoinduced absorption

Summary form only given. The intrinsic dynamics of photoexcited carriers in oxygen-free C/sub 60/ film and their remarkable evolution as the film is exposed to oxygen are revealed by transient and steady-state photoconductivity measurements at various temperatures, light intensities and photon energies, as well as by transient photoinduced absorption in the picosecond time regime. Exposure of C/sub 60/ film to oxygen creates deep traps which reduce drastically the carrier lifetime and consequently the room temperature steady-state photoconductivity by three to six orders of magnitude. Oxygen affects the steady-state photoconductivity excitation spectrum in qualitative similar way as decreasing the ambient temperature; in both cases the photoconductivity decreases faster when carriers are excited below the band edges. The transient and steady-state PC of C/sub 60/ film fully exposed to oxygen become temperature independent. While exposing the sample to oxygen changes dramatically the photoconductivity, it does not affect significantly the optical absorption as well as the transient photoinduced absorption in the picosecond time regime.