| Abstrakt: |
We have employed quantum chemical methods, at the local spin density approximation level, to study the interaction between an organic semiconductor, polythiophene, and potential metals for hole injecting contacts in devices: vanadium, chromium, copper, and gold. The results show that there is a strong interaction between vanadium and the thiophene ring, mainly due to covalent bond formation between the metal and the S and Cα atoms of the thiophene. Vanadium is therefore predicted to provide good conditions for chemisorption and mechanical stability at the polymer/contact interface. A similar, but considerably weaker, covalent interaction is found between chromium and all the conjugated atoms of the thiophene molecule. For both these metals, the interactions cause the thiophene ring to lose its aromaticity and planarity which, as a consequence, would interrupt the π-electron system in a polymer and impair charge transport along the chains. In the case of copper, the metal is found to react only with the sulfur atom of the thiophene and to a very small extent. For gold, the results indicate that there are no significant chemical interactions. Our results are in good qualitative agreement with XPS measurements performed during metallization of thin films of poly(3-hexylthiophene). The calculations confirm the general trend of reactivities for this series of metals: V>=Cr>=Cu>=Au=0. © 1995 American Institute of Physics. [ABSTRACT FROM AUTHOR] |
