Photoluminescence characteristics of green and blue emitting Alq3 organic molecules in crystals and thin films

Alq3 is synthesized by mixing 8-quinolinol and Al(OH)3 in distilled water at about 95 °C. The reaction time of 24 and 100 h leads to α- and γ-rich Alq3, respectively. The α-rich Alq3 is converted to γ-Alq3 after annealing at 400 °C, while sublimation at 330 °C destroys γ-Alq3. The mer- and fac-isomers give the same vibronic structure in the photoluminescence (PL) spectra at 12 K, which is composed of a progression of vibrational energy of 660 cm− 1, but the PL band peak of fac-isomer is blue-shifted by about 34 nm with respect to that of mer-isomer. When the temperature is increased from 12 K to 296 K, the PL intensity is observed to decrease above 100 K by non-radiative bimolecular recombination.