Enhanced luminescence properties of hybrid Alq3/ZnO (organic/inorganic) composite films

Pristine tris-(8-hydroxyquionoline)aluminum(Alq3) and (Alq3/ZnO hybrid) composites containing different weight percentages (5 wt%, 10 wt%, 20 wt%, 30 wt%, 40 wt% and 50 wt%) of ZnO in Alq3 were synthesized and coated on to a glass substrate using the dip coating method. The optimum concentration of ZnO in Alq3 films to get the best luminescence yield has been identified. XRD pattern reveals the amorphous nature of pure Alq3 film. The Alq3 films containing different weight percentages of ZnO show the presence of crystalline ZnO in Alq3/ZnO composite films. The FTIR spectrum confirms the formation of quinoline with absorption in the region 600−800 cm−1. The hybrid Alq3/ZnO composite films indicate the presence of Zn−O vibration band along with the corresponding Alq3 band. The band gap (HOMO-LUMO) of Alq3 film was calculated using absorption spectra and it is 2.87 eV for pristine films while it is 3.26 eV, 3.21 eV, 3.14 eV, 3.10 eV, 3.13 eV and 3.20 eV for the composite films containing 5-50 wt% of ZnO. The photoluminescence (PL) spectra of Alq3 films show a maximum PL intensity at 514 nm when excited at 390 nm. The ZnO incorporated composite films (Alq3/ZnO) exhibit an emission in 485 nm and 514 nm. The composite films containing 30 wt% of ZnO exhibit maximum luminescence yield.