Electronic structure of metal quinoline molecules from G0 W0 calculations

The photoemission spectra of four different metal quinoline molecules, namely, the prototypical tris(8-hydroxyquinolinato)-aluminum(III) (Alq(3)) complex and the related compounds Gaq(3), Inq(3), and tris-(9-hydroxyphenalen-1oate)-aluminum(III) [Al(OP)(3)] are compared to the electronic structure computed with different first-principles methods. In general, we found that, for Alq(3), Gaq(3), and Inq(3), the molecular orbitals obtained with density functional theory and hybrid functionals represent a good approximation to the quasiparticle states. The same conclusion can be partially extended to the interesting case of Al(OP)(3), although a direct comparison between theoretical and experimental results appears rather difficult for states, which are lower in energy than the first ten highest occupied molecular orbitals. Taking our results as a starting point we critically discuss the different available experimental data concerning the charge transport gap of Alq(3).