Epitaxial growth of di- <i>n</i> -alkylated perylene-3,4:9,10-bis(dicarboximide)s (PTCDIs) on single-crystal dinaphtho[2,3- <i>b</i> :2′,3′- <i>f</i> ]thieno[3,2- <i>b</i> ]thiophene (DNTT)

Abstract Well-defined interfaces between molecular semiconductors formed on molecular single-crystal substrates have provided fundamental insights into the functional interfaces of organic electronic devices. However, despite the practical importance of alkyl-substituted semiconductor molecules for solution-processable device fabrication, the effects of aliphatic side groups on interfacial structures and growth mechanisms remain insufficiently understood. In this study, well-defined molecular interfaces formed by N , N ’-di- n -alkyl-3,4,9,10-perylenetetracarboxylic diimide (PTCDI-C x ) on single crystals of dinaphtho[2,3- b :2′,3′- f ]thieno[3,2- b ]thiophene (DNTT) were systematically investigated using surface X-ray diffraction with synchrotron radiation, while varying the alkyl chain length of PTCDI-C x over the range 1 ≤ x ≤ 8. Epitaxial crystalline growth of PTCDIs on DNTT was confirmed for all chain lengths except PTCDI-C4 and PTCDI-C7. Although the molecular arrangements of PTCDI-C5, PTCDI-C6 and PTCDI-C8 were largely similar, both crystallinity and molecular orientations exhibited pronounced changes with increasing chain length for x ≥ 4, presumably due to weakened intermolecular interactions associated with shorter alkyl substituents.