Berlin 2005 – scientific programme
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SYOO: Organic Optoelectronics and Photonics
SYOO 6: Poster
SYOO 6.26: Poster
Monday, March 7, 2005, 18:00–20:00, Poster TU A
The Effect of Oxygen Exposure on Pentacene Electronic Structure — •A. Vollmer1, O. D. Jurchescu2, I. Arfaoui2, P. Rudolf2, T. T. M. Palstra2, J. Niemax3, J. Pflaum3, I. Salzmann4, J. P. Rabe4, and N. Koch4 — 1BESSY, Albert-Einstein-Str. 15, D-12489 Berlin — 2Materials Science Center, Rijksuniversiteit Groningen, NL-9747 AG Groningen, Netherlands — 3Universität Stuttgart, 3. Physikalisches Institut, D-70550 Stuttgart — 4Humboldt-Universität zu Berlin, Institut f. Physik, D-12489 Berlin
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. This study is motivated by the fact that a reliable comparison between charge carrier mobility values from different laboratories is often hampered by the variation of sample preparation and environmental conditions for measurements. We find that molecular oxygen and water do not react noticeably with pentacene, whereas ozone readily oxidizes the organic compound. Oxygen diffusion through pentacene thin films and single crystal surfaces is reversible, and does not leave behind (after re-evacuation) electrically active electronic states that would lead to p-type doping of the organic bulk. However, oxygen exposure lowers the hole injection barrier at the interface between Au and pentacene by 0.25 eV, presumably due to a modification of the Au surface properties.