Highly Efficient Au(I) Alkynyl Emitters: Thermally Activated Delayed Fluorescence and Solution-Processed OLEDs.

Two-coordinate donor-metal-acceptor type coinage metal complexes displaying efficient thermally activated delayed fluorescence (TADF) have been unveiled to be highly appealing candidates as emitters for organic light-emitting diodes (OLEDs). Herein a series of green to yellow TADF gold(I) complexes with alkynyl ligands has been developed for the first time. The complexes exhibit high photoluminescence quantum yields (PLQYs) of up to 0.76 in doped films (5 wt % in PMMA) at room temperature. The modifications of alkynyl ligands with electron-donating amino groups together with the use of electron-deficient carbene ligands induce ligand-to-ligand charge transfer excited states that give rise to TADF emission. Spectroscopic and density functional theory (DFT) calculations reveal the roles of electron-donating capability of the alkynyl ligand in tuning the excited-state properties. Solution-processed organic light-emitting diodes (OLEDs) using the present complexes as emitters achieve maximum external quantum efficiency (EQE) of up to 20 %.