Approaches to Stabilized HOMO/LUMO Levels in Blue Emissive Carbene-Metal-Amides

Two-coordinate, coinage metal carbene-metal-amide (cMa) emitters have garnered attention due to their near unity photoluminescence quantum yields, color tunability, and short radiative lifetimes. However, due to their intrinsically high energy HOMO and LUMO levels, there has been difficulty incorporating them into charge balanced organic light-emitting diodes (OLEDs). Here, four new cMa complexes were prepared where the HOMO was stabilized by using cyano or trifluoromethyl electron withdrawing groups on the donor moiety and the LUMO was stabilized using a carbene acceptor with a low reduction potential. These modifications resulted in cMa complexes with sky-blue emission, high quantum yields (Φ_PL > 0.95), and short radiative lifetimes (τ = 225 ns). The resultant vacuum-deposited OLED devices based on ${\mathrm{Au}}_{\mathrm{Bim}{\left(C{F}_3\right)}_2}^{\mathrm{PAC}}$ with SiCzCz/SiTrzCz₂ cohost system display blue electroluminescence at 470 nm and external quantum efficiency of 8%.