THE EFFECT OF OXYGEN ON THE PHOTOCONDUCTIVITY OF C-60 FILM - ACTION SPECTRUM AND TEMPERATURE-DEPENDENCE

We report the effect of oxygen on the action spectrum of the steady-st ate photoconductivity (PC) of C-60 film and its temperature dependence . The steady-state PC decreases more than 4 orders of magnitude upon e xposure to oxygen; the PC decreases faster below HBAR omega approximat e to 2.3 eV. The low-temperature PC spectrum of the oxygen-free C-60 i s similar to the high-temperature PC spectrum of C-60 exposed to oxyge n. The steady-state PC exhibits a peak at T approximate to 240 K in th e oxygen-free C-60, which disappears in C-60 exposed to oxygen. The re sults indicate that the oxygen in C-60 film acts as an efficient deep trap for photoexcited carriers and reduces the structural order.