Metal/Alq3 interactions in organic light emitting devices: The different roles of Mg, Al, and Li atoms

The geometrical and electronic structures of tris(8-hydroxy-quinoline) aluminum (Alq₃) molecule interacting with metals like magnesium, aluminum and lithium used in organic light emitting devices were studied by first principle calculations using density functional theory. The favourable complexation for the interacting systems was the metal atom inserting into the core of the Alq₃ molecule with the metal atom bridging two oxygen atoms and being coplanar with one of the quinoline ligands. The calculated electronic structures showed that there were only slight changes in the Alq₃ frontier orbitals for Mg-Alq₃and Li-Alq₃ complexations.