EFFECT OF LOW-TEMPERATURE ANNEALING ON STRUCTURE AND OPTICAL PROPERTIES OF AMORPHOUS TRIS(8-HYDROXYQUINOLINE) ALUMINUM FILMS

Abstract

Needle-shaped nanostructured tris(8-hydroxyquinoline) aluminum nanowires (Alq3) have been obtained by annealing Alq3 amorphous films at 150∘C which is lower than the glass transition temperature of Alq3 (172∘C). The growth of Alq3 nanowires is attributed to the migration and stacking of Alq3 molecules which acquire thermal energy from the annealing process. X-ray diffraction analysis and scanning electronic microscopy spectra show that the Alq3 nanowires are composed of the well-known [Formula: see text]-phase Alq3. The intensity of the photoluminescence spectra firstly increases and then decreases as the annealing time increases, along with a spectral blue shift. The optical transmittance spectra of the annealed Alq3 films show a smaller average absorption in the visible range and a wider optical bandgap compared with that of the amorphous films, as a result of the decrease of [Formula: see text] overlapping in the Alq3 molecules.