Abstract
2,2′:6′,2″-Ternaphthalene (NNN) is a novel, blue-emitting material, suitable for preparation of organic light-emitting diodes. Its crystal structure has been solved recently, but its thermal behavior and surface properties have not yet been explored, partly due to the difficulty in obtaining high quality crystals. In the present study we use classical molecular dynamics to investigate the thermal behavior of bulk and (001) surfaces of NNN. Our bulk simulations indicate the occurrence of a phase transition at about 600 K. The transition is facilitated by the presence of a free (001) surface, since a reconstruction leading to a very similar structure occurs around 550 K in our surface models. This holds for both ideal and defective surface models, containing a small number of vacancies (one or two missing molecules in the outermost layer). In all cases, the process is triggered by thermal motion and involves the reorientation of the molecules with respect to the (001) plane. Both the bulk and surface phases share the monoclinic space group P21/a with a herringbone disposition of molecules. These findings and their implications for the use of NNN in organic electronics are discussed.
Highlights
Years of intensive research on organic electronic devices have taught us that supramolecular interactions and organization have a major influence on their final performance
When these polymorphs are distinct from those observed in bulk crystals, one may speak of surfaceinduced phases (SIPs)
This work aims to set up a background knowledge about surface features of NNN (001), the low energy face displayed by thin films, by means of classical Molecular dynamics (MD)
Summary
Years of intensive research on organic electronic devices have taught us that supramolecular interactions and organization have a major influence on their final performance. Connected to the preparation of devices, e.g., by vacuum deposition techniques or with solution methods, the sword of Damocles of polymorphism is always present, definitely a widespread phenomenon when dealing with molecular crystals.[1] Polymorphism in bulk phases is a general issue in several fields, including pharmaceuticals and materials science. In thin films the suitable form for a realistic exploitation of electronic materials occurrence of polymorphism is further enhanced by the presence of the substrate surface and/or strong kinetic effects during growth. When these polymorphs are distinct from those observed in bulk crystals, one may speak of surfaceinduced phases (SIPs).
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
