Berlin 2005 – wissenschaftliches Programm

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SYOO: Organic Optoelectronics and Photonics

SYOO 6: Poster

SYOO 6.26: Poster

Montag, 7. März 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.