Thermally Activated Delayed Fluorescence from d10 -Metal Carbene Complexes through Intermolecular Charge Transfer and Multicolor Emission with a Monomer-Dimer Equilibrium.

Abstract

A series of two‐coordinate AuI and CuI complexes (3 a, 3 b and 5 a, 5 b) are reported as new organometallic thermally activated delayed fluorescence (TADF) emitters, which are based on the carbene–metal–carbazole model with a pyridine‐fused 1,2,3‐triazolylidene (PyTz) ligand. PyTz features low steric hindrance and a low‐energy LUMO (LUMO=−1.47 eV) located over the π* orbitals of the whole ligand, which facilitates intermolecular charge transfer between a donor (carbazole) and an accepter (PyTz). These compounds exhibit efficient TADF with microsecond lifetimes. Temperature‐dependent photoluminescence kinetics of 3 a supports a rather small energy gap between S1 and T1 (ΔE S1-T1 =60 meV). Further experiments reveal that there are dual‐emission properties from a monomer–dimer equilibrium in solution, exhibiting single‐component multicolor emission from blue to orange, including white‐light emission.