Molecular dynamics study of N,N'-di-n-alkyl-3,4,9,10-perylenetetracarboxylic diimide (PTCDI)/rubrene interface: Why the charge transfer at the interface is optimized depending on the alkyl chain length of PTCDI.

Abstract

Molecular dynamics simulations were performed to investigate the interfacial structure of the N,N'-di-n-alkyl-3,4,9,10-perylenetetracarboxylic diimide (PTCDI)/rubrene interface, which represents the donor/acceptor interface in new types of organic light-emission diodes. In particular, the interfacial structure was examined for different alkyl chain lengths of PTCDI (Cn-PTCDI) at n = 4, 8, and 13, in order to elucidate the observed maximum charge transfer efficiency at the C8-PTCDI/rubrene interface in a recent experiment. The results revealed that the molecular conformation of the acceptor (Cn-PTCDI) molecules at the interface undergoes changes depending on the alkyl chain length when interacting with the rubrene molecule. It was found that the closest complex between Cn-PTCDI and rubrene is formed at n = 8, consistent with the experimental observation. In addition, the interfacial structures of Cn-PTCDI/air and rubrene/air were examined and compared to gain insights into the inherent stability associated with the intermolecular interactions at the interface.