Study of Alq3 thermal evaporation rate effects on the OLED

Electrical and optical characteristic, surface morphology and nitrogen/carbon ratio of tris-(8-hydroxyquinoline) aluminum (Alq3) were studied as a function of thermal evaporation rate. When the deposition rate increased from 0.3 to 1.5 A/s, the luminescence efficiency of OLED increased about three times. The X-ray photoelectron spectroscopy (XPS) measurements showed that as the Alq3 deposition rate increased, the film had less N-containing species. AFM measurements showed that the surface roughness of the Alq3 films decreased from 4.4 to 1.0 nm with deposition rates. These changed Alq3 film composition and surface morphology are believed to have effects on the electrical and luminance performance.