Singlet to triplet excitation spectrum of thin film tris-(8-hydroxyquinolate)-aluminium in direct absorption

We report the excitation spectrum of a similar to 185 nm thick layer tris-(8-hydroxyquinolate)-aluminium, vapour deposited on a 100 mu m thick borosilicate microscopy cover glass, in the 1.9-2.4 eV range using a conventional cavity-ringdown spectrometer setup. The spectrum is collected at room temperature in ail open cavity. It shows abroad loss structure with a maximum around 2.1 eV and a width of similar to 0.2 eV. The spectrum is in conformity with literature phosphorescence spectra and with literature TDDFT Computed T-1 <- S-0 transition energies. The observed loss structure can be attributed to the T-1 <- S-0 absorption band of tris-(8-hydroxyquinolate)-aluminium. (C) 2008 Elsevier B.V. All rights reserved.