Conformationally flexible “Carbene–Metal–Amide” (CMA) complexes of copper and gold show photoemissions across the visible spectrum, including mechanochromic behavior which led to the first CMA-based white light-emitting OLED.

New luminescent "carbene-metal-amide" (CMA) Cu, Ag and Au complexes based on monocyclic (C6) or bicyclic six-ring (BIC6) cyclic (alkyl)(amino)carbene ligands illustrates the effects of LUMO energy stabilization, conformational flexibility, excited state energy and geometry on the photoluminescent properties, leading to 100% luminescence quantum yields, short excited state lifetimes Cu > Au > Ag down to 0.5 µs and high radiative rates of 10 6 s -1 . Gold complexes with the BIC6 ligand exhibit exceptional photostability under hard and soft UV-light compared with analogous complexes with C5 and C6 carbenes. Steady-state and time-resolved photoluminescence spectroscopy at 298 K and 77 K enabled an estimate of the energy levels of the charge transfer (CT) and locally excited (LE) states with singlet and triplet character. A four-state model is applied to describe thermally activated delayed fluorescence (TADF) properties in CMA materials and correlates excited state lifetimes with the energy difference between LE and CT states.

Carbene-metal-amide type photoemitters based on CF3-substituted carbazolate ligands show sky-blue to deep-blue photoluminescence from charge-transfer excited states. They are suitable for incorporation into organic light-emitting diodes (OLEDs) by thermal vapour deposition techniques, either embedded within a high-triplet-energy host, or used host-free. We report high-efficiency OLEDs with emission ranging from yellow to blue (Commission Internationale de l'Éclairage (CIE) coordinates from [0.35, 0.53] to [0.17, 0.17]). The latter show a peak electroluminescence external quantum efficiency (EQE) of 20.9 % in a polar host. We observe that the relative energies of CT and 3 LE states influence the performance of deep-blue emission from carbene-metal-amide materials. We report prototype host-free blue devices with peak external quantum efficiency of 17.3 %, which maintain high performance at brightness levels of 100 cd m -2 .