Harvesting all electrogenerated excitons through metal assisted delayed fluorescent materials.

Highly efficient and stable palladium complexes that exhibit both phosphorescence and delayed fluorescence are developed. It is demonstrated that the emission from the two processes can be separately tuned through rational ligand modification. External quantum efficiencies over 20% are achieved and stable devices demonstrate an operational lifetime to 90% initial luminance estimated at over 20 000 h at 100 cd m(-2) .