Amorphous-to-Crystalline Phase Transformation of Thin Film Rubrene

Abstract

We report on the amorphous-to-crystalline phase transformation of rubrene thin films. The crystallization of the organic thin films displays disk-like domains whose nucleation and growth follow phase transformation kinetics well-established for inorganic materials under certain time and temperature conditions. We understood that the crystallization of amorphous rubrene thin film shows site-saturated nucleation behavior while the crystalline growth involves both diffusion and interface-controlled kinetics displaying spherulitic disk growth behavior. The activation energy of the transformation kinetics was about 0.78 eV on hexamethyldisilazane-functionalized SiO(2) substrate as mostly consumed at the growth process. The crystallization kinetics changes with the film substrate; more hydrophobic substrate induces a lesser number of crystalline nuclei while causing faster growth of those nuclei.

Vibrational modes and changing molecular conformation of perfluororubrene in thin films and solution

“…III C focusses on the correlation of morphology and conformation of the molecules. 24,43,44 Interestingly, we find a connection between dewetting and a change in the molecular conformation for the thin film on SiO 2 .…”

Competition between polaron pair formation and singlet fission observed in amorphous rubrene films

“…The morphology does not exhibit either large grains or islandlike crystalline domains, which have been reported for crystalline rubrene films. 12,13 Park et al 13 observed the growth of these domains only after annealing the films at higher-thanroom temperatures, whereas our films were measured just after evaporation at room (or lower) temperatures. Furthermore, no steplike structures with step widths in the range of 1 μm or larger, characteristic of single crystal films, have been observed.…”

Temperature-dependent singlet exciton fission observed in amorphous rubrene films

“…It is generally found by different researchers that the obtained rubrene films usually exhibit amorphous morphology [16][17][18]. Park et al observed the growth of island-like crystalline domains only after annealing the films at higher-than-room temperatures [18].…”