Photoluminescence and Electroluminescence of Organic Light Emitting Diodes Based on Tris-(8-quinolinolato) Aluminum Nanoparticles

Tris-(8-quinolinolato) aluminum (AlQ3) organic nanoparticles with an average diameter 20 nm were prepared through a reprecipitation method. The AlQ3 nanoparticles are spherical and the average particle size does not change by varying the aging time. The photoluminescent and electroluminescent properties were investigated via the AlQ3 nanoparticles and the device based on the AlQ3 nanoparticles, respectively. Blue shift of both the photoluminescence and electroluminescence spectra for the AlQ3 nanoparticles was observed. With increasing the driving bias, the maximum EL emission peak of the AlQ3 nanoparticles was shifted to longer wavelength. The maximum luminance and luminous efficiency of the AlQ3 nanoparticle-based device are about 600 cd/m2 at driving bias 16V and 0.19 cd/A at a current density of 150 mA/cm2, respectively. The obvious quantum size effect of electro-luminescence devices with the AlQ3 nanoparticles has been proved, which will open a useful route and new studying field of organic electronic devices, and the study of the fundamental process connecting both of those more conventional classes of materials, i.e., organic molecular crystals.