Morphological phase transitions in image films

Thin films of tris(8-hydroxyquinoline)aluminum (image) have been subjected to thermal processes in order to verify previous reports about improved emission efficiency upon heating organic light-emitting diodes (OLEDs). It has been found that annealed films in various atmospheres display an abrupt variation of the intensity, peak wavelength and linewidth of the photoluminescence band between 150 and image, which hint at phase transition phenomena. Moreover, the annealed films exhibit a much longer lifetime, which is still one of the major challenges in the OLEDs research field.