High‐Efficiency Tris(8‐hydroxyquinoline)aluminum (Alq 3 ) Complexes for Organic White‐Light‐Emitting Diodes and Solid‐State Lighting

Combinations of electron‐withdrawing and ‐donating substituents on the 8‐hydroxyquinoline ligand of the tris(8‐hydroxyquinoline)aluminum (Alq 3 ) complexes allow for control of the HOMO and LUMO energies and the HOMO–LUMO gap responsible for emission from the complexes. Here, we present a systematic study on tuning the emission and electroluminescence (EL) from Alq 3 complexes from the green to blue region. In this study, we explored the combination of electron‐donating substituents on C4 and C6. Compounds 1 – 6 displayed the emission tuning between 478 and 526 nm, and fluorescence quantum yield between 0.15 and 0.57. The compounds 2 – 6 were used as emitters and hosts in organic light‐emitting diodes (OLEDs). The highest OLED external quantum efficiency (EQE) observed was 4.6 %, which is among the highest observed for Alq 3 complexes. Also, the compounds 3 – 5 were used as hosts for red phosphorescent dopants to obtain white light‐emitting diodes (WOLED). The WOLEDs displayed high efficiency (EQE up to 19 %) and high white color purity (color rendering index (CRI≈85).