Preparation and Characterization of Blue‐Luminescent Tris(8‐hydroxyquinoline)‐aluminum (Alq3)

Using differential scanning calorimetry (DSC) measurements in combination with structural and optical characterization we have investigated the formation conditions of different phases of tris(8‐hydroxyquinoline)aluminum (Alq₃). We have identified the δ‐phase as a high‐temperature phase of Alq₃ being composed of the facial stereoisomer, and report an efficient method to obtain blue luminescent Alq₃ by a simple annealing process. This allows the preparation of large amounts of pure δ‐Alq₃ by choosing appropriate annealing conditions, which is necessary for further characterization of this blue‐luminescent phase, and offers the possibility of fabricating blue organic light‐emitting devices (OLEDs) from this material.