The interaction of oxygen and ozone with pentacene

We use ultraviolet photoemission spectroscopy (UPS) to investigate the effect of oxygen and air exposure on pentacene thin film electronic structure. It is found that O2 and water do not react noticeably with pentacene on the timescale of several hours, whereas a mixture of oxygen atoms, singlet oxygen and ozone readily oxidizes the organic compound. We obtain no evidence for irreversible intercalation of oxygen into pentacene or considerable p-type doping after re-evacuation. Infrared spectroscopy and atomic force microscopy are used to study the oxidation of pentacene thin films. Our data suggest the oxidation of pentacene with reactive oxygen species to yield highly volatile reaction products as evidenced by significant mass-losses of the films.