Oxygen and water defect formation processes in pentacene.

Organic thin-film devices have emerged as promising candidates for novel electronic applications. Unlike traditional solid-state devices, the weak intermolecular non-covalent bonding of organic thin films leads to flexibility and possible pattern formation. The same mechanism, however, is responsible for the appearance of a variety of defects that may interfere with film growth and are potentially detrimental to the desired transport properties. Here we use first-principles calculations to study defect formation processes in the prototypical system of pentacene. In particular, we report on defect configurations of oxygen and water molecules in bulk pentacene and ultra-thin films on Si-based substrates. The results show that several stable configurations of such defects exist. Their presence has a direct bearing on growth processes and transport properties through strong covalent bonding and induced molecular distortions in their vicinity. This work was supported in part by DOE Grant DEFG0203ER46096.