Roles of Ancillary Chelates and Overall Charges of Bis-tridentate Ir(III) Phosphors for OLED Applications.

A series of charge-neutral bis-tridentate Ir(III) complexes (, , and ) were prepared via employing three distinctive tridentate prochelates, that is, (pzpph)H, [(phpyim)H·(PF)], and [(pimb)H·(PF)], which possess one dianionic pzpph, together with a second monoanionic tridentate chelate, namely, (pzpph)H, phpyim, and pimb, respectively. Moreover, a homoleptic, charge-neutral complex was obtained by methylation of chelating (pzpph)H of in basic media, while closely related cationic complexes were obtained by further methylation of the remaining pyrazolate unit of previously mentioned neutral complexes , followed by anion metatheses. All of these Ir(III) metal complexes showed a broadened emission profile with an onset at ∼450 nm, a result of an enlarged ligand-centered ππ* transition gap, but with distinct efficiencies ranging from 0.

Facile Generation of Thermally Activated Delayed Fluorescence and Fabrication of Highly Efficient Non-Doped OLEDs Based on Triazine Derivatives.

A series of donor-acceptor-donor triazine-based molecules with thermally activated delayed fluorescence (TADF) properties were synthesized to obtain highly efficient blue-emitting OLEDs with non-doped emitting layers (EMLs). The targeted molecules use a triazine core as the electron acceptor, and a benzene ring as the conjugated linker with different electron donors to alternate the energy level of the HOMO to further tune the emission color. The introduction of long alkyl chains on the triazine core inhibits the unwanted intermolecular D-D/A-A-type π-π interactions, resulting in the intermolecular D-A charge transfer.