Au(I)-TADF Emitters for High Efficiency Full-Color Vacuum-Deposited OLEDs and TADF-Sensitized Fluorescent OLEDs with Ultrahigh Brightness and Prolonged Operational Lifetime

Herein a class of structurally simple and operationally stable Au(I)-TADF (TADF = thermally activated delayed fluorescence) materials, based on a carbene-metal-amide (CMA) molecular scaffold comprised of sterically bulky N-heterocyclic carbene ligands with N-heterocyclic & pi;-annulation, are reported. These CMA(Au) emitters are thermally stable, adopt coplanar or orthogonal geometry between the carbene and amide ligands, and show strong blue to deep red TADF emissions (466-666 nm) from thermally equilibrated singlet ligand-to-ligand-charge-transfer excited states with emission quantum yields of 0.63-0.99 and radiative decay rate constants of 0.68-3.2 x 10(6) s(-1) in thin film samples at room temperature. The effects of increasing & pi;-extension and orthogonal molecular geometry are similarly manifested in the reduction of both singlet-triplet energy gap and S-1 transition dipole moment. The vacuum-deposited Au(I) organic light-emitting diodes (OLEDs) display superior electroluminescence characterized by ultrahigh brightness up to 300 000 cd m(-2) and external quantum efficiencies (EQEs) up to 26.2% with roll-offs down to 2.6% at 1000 cd m(-2) alongside record-setting device lifetimes (LT95) up to 2082 h. Ultrapure-green TADF-sensitized fluorescent OLEDs employing the CMA(Au) emitter as sensitizer and a multiresonance terminal emitter achieve EQEs of up to 25.3%.

Automated summary

This article reports a class of structurally simple and operationally stable Au(I)-TADF materials based on a carbene-metal-amide (CMA) molecular scaffold. These CMA(Au) emitters show strong TADF emissions and high radiative decay rate constants in thin film samples. The vacuum-deposited Au(I) OLEDs exhibit superior electroluminescence with high brightness, high external quantum efficiencies, and long device lifetimes. The CMA(Au) emitter can also be used as a sensitizer in TADF-sensitized fluorescent OLEDs to achieve high EQEs.