The Effect of Defects on the Transport Properties of Rubrene
David V. Lang
Dept of Applied Physics and Applied Math, Columbia University, New York, NY
We have extended our earlier studies of defects in pentacene single crystals to rubrene
and have found similar results. Namely, the properties of purified rubrene single crystals
are significantly influenced by extrinsic factors, such as impurities, defects, and defect
reactions. In this talk I will review the latest experimental results on this subject from
the Bell Labs/Columbia organic single crystal project. In particular, I will discuss the
unusual behavior of the rubrene photoconductivity – the long persistence times in the
dark and the dependence on ambient conditions, such as temperature, light exposure, and
the influence of oxygen vapor pressure. I will show that these results are very similar to
the well-understood behavior of anthracene photoconductivity, which is also dominated
by extrinsic factors. Finally, I will discuss some of our group’s results on defects in
crystalline rubrene FETs.