1,3-Diketone Ligand Compound for OLED Efficiency Roll-off

The patent introduces bulky substituent groups (such as tert-butyl groups, adamantyl groups, or dendrimer groups) at specific positions of the ligand structure to segment the molecular packing arrangement. This segmentation prevents close contact between phosphorescent material molecules, thereby suppressing aggregation quenching while maintaining high internal quantum efficiency.

The patent modifies specific local regions of the ligand structure by introducing electron-donating or electron-withdrawing substituent groups at defined positions (such as positions 2, 3, 4, 5, or 6 of the ligand ring system). This local quality modification optimizes the balance between luminescence efficiency and aggregation resistance by controlling molecular interactions at critical sites.

By incorporating bulky substituent groups that segment molecular packing, the patent increases the effective distance between phosphorescent molecules. This spatial segmentation allows higher doping concentrations to be used for improved brightness while preventing the molecular proximity required for triplet-triplet annihilation.

The patent employs three-dimensional dendrimer groups or bulky cyclic structures that extend in multiple spatial dimensions. This dimensional approach creates a protective steric barrier around each phosphorescent molecule, preventing harmful interactions even at high concentrations required for high brightness applications.

The patent creates composite ligand structures by combining the core phosphorescent metal complex (such as iridium or platinum) with specially designed organic ligands containing stable aromatic systems (such as cyclometalating ligands with fused ring structures). This composite approach integrates the high quantum efficiency of the metal complex with the thermal stability of the robust organic ligand framework.

The patent systematically varies structural parameters of the ligand, such as increasing aromatic ring fusion, introducing rigid cyclic structures, and adjusting substituent positions, to optimize the thermal stability parameter while preserving the photophysical properties required for high phosphorescence quantum efficiency.