The effect of oxygen exposure on pentacene electronic structure

We use ultraviolet photoelectron spectroscopy to investigate the effect of oxygen and air exposure on the electronic structure of pentacene single crystals and thin films. it is found that O-2 and water do not react noticeably with pentacene, whereas singlet oxygen/ozone readily oxidize the organic compound. Also, we obtain no evidence for considerable p-type doping of pentacene by O-2 at low pressure. However, oxygen exposure lowers the hole injection barrier at the interface between An and pentacene by 0.25 eV, presumably due to a modification of the An surface properties.