Probing the transitions between morphological phases in an oligofluorene thin-film using temperature-dependent photoluminescence spectroscopy

We study the transitions between morphological phases of an oligofluorene (pentamer) thin-film using temperature-dependent photoluminescence emission. We find that the so-called β-phase can be created by cooling an amorphous thin-film to 80 K and then slowly returning it to room-temperature. This process is however suppressed if the thin-film is initially prepared in a poly-crystalline form. We also demonstrate that the presence of molecules in the β-phase suppresses the room-temperature crystallization that otherwise occurs in an amorphous film.