Effect of thermal annealing on the structural and optical properties of tris‐(8‐hydroxyquinoline)aluminum(III) (Alq 3 ) films

Tris‐(8‐hydroxyquionoline)aluminum (Alq 3 ) was synthesized and coated on to a glass substrate using the dip coating method. The structural and optical properties of the Alq 3 film after thermal annealing from 50°C to 300°C in 50° steps was studied. The films have been prepared with 2 to 16 layers (42–324 nm). The thickness and thermal annealing of Alq 3 films were optimized for maximum luminescence yield. The Fourier transform infrared spectrum confirms the formation of quinoline with absorption in the region 700 − 500/cm. Partial sublimation and decomposition of quinoline ion was observed with the Alq 3 films annealed at 300°C. The X‐ray diffraction pattern of the Alq 3 film annealed at 50°C to 150°C reveals the amorphous nature of the films. The Alq 3 film annealed above 150°C were crystalline nature. Film annealed at 150°C exhibits a photoluminescence intensity maximum at 512 nm when excited at 390 nm. The Alq 3 thin film deposited with 10 layers (220 nm) at 150°C exhibited maximum luminescence yield. Copyright © 2014 John Wiley & Sons, Ltd.