Near-Infrared Ytterbium Complexes Based on Polycyclic Aromatic Dicarboxylate Ligands and the Solution-Processed NIR OLED with Irradiance up to 110,284 μW/m.

Since the O-H and N-H oscillators of solvent molecules attached to ytterbium ion (Yb) and C-H oscillators existing in the inner coordination sphere of Yb would quench the excited energy of Yb(III), which leads to low quantum yields (QYs) of Yb(III) complexes, we aimed to design a ligand that could block solvent molecules and C-H oscillators out of the first coordination sphere of Yb. Herein, a series of novel polycyclic aromatic dicarboxylate ligands are designed and synthesized to effectively protect Yb from solvent molecules and efficiently sensitize Yb luminescence, while the cost and sophistication of the synthesis are satisfactory. Therein, [Yb(MO-DPyPDA)](DIEA) exhibited a considerable QY of 5.20% and a long luminescent lifetime of 102 μs in CDOD. The single-crystal structure demonstrates that there are no solvent molecules and C-H oscillators existing in the inner coordination sphere of Yb, which is conducive to alleviating the quenching effect. Meanwhile, we also carried out experiments to verify that it was thermodynamically feasible for ligands to sensitize the luminescence of center ion through internal redox processes. Moreover, several groups of near-infrared organic light-emitting diodes based on [Yb(DTFM-DPyPDA)](DIEA) were fabricated based on the solution-processing method, and the highest irradiance of 110,284 μW/m was realized by optimizing the device structure.