Photoluminescence spectroscopy study on tris(8-hydroxyquinoline) aluminum film

Abstract In situ photoluminescence spectroscopy (PL) measurements of tris(8-hydroxyquinoline) aluminum (Alq 3 ) film were carried out. Upon deposition of Alq 3 on the glass substrate, the PL intensity changes dramatically, while the peak position of Alq 3 emission shows a sharp red-shift from 524 nm at the initial deposition of Alq 3 , and tends to a saturation value of 536 nm for the film thickness range from 2 to 500 nm. This red-shift is associated with the change from the 2D to 3D exciton state with increasing Alq 3 film thickness. Temperature dependent PL spectra of Alq 3 films showed, besides the changes in the PL intensity, clearly a blue-shift of Alq 3 emission about 9 nm for the film annealing up to 150 °C, while no any shift of Alq 3 emission was observed for the film annealing below 130 °C. Both changes in PL intensity, and especially in the peak position of Alq 3 emission were attributed to crystallization (thermal) effect of Alq 3 film upon annealing.