Intermolecular Charge Transfer Induced Sensitization of Yb in β-Diketone Coordination Compounds with Excellent Luminescence Efficiency.

Achieving high quantum yields for Yb ion emission in complexes with organic ligands is a challenging task, as most Yb complexes with such ligands typically exhibit efficiencies below 3.5%. Our research demonstrates that the introduction of heavy atom-containing ancillary ligands, such as TPPO or TPAO, along with the careful engineering of the main β-diketone ligand, can increase the luminescence efficiency up to 20-fold by the alteration of the energy migration pathway. It is demonstrated that the combination of two distinct organic ligands leads to the blockage of singlet-triplet intersystem crossing (ISC), alongside electronic energy transfer from β-diketone to Yb ions through charge transfer states. The synthesized complexes exhibit quantum yields of 6.5% and 7.0% in the solid state, which places them at the top globally among this class of materials with simple non-deuterated and non-fluorinated ligands.