Equalized Dual Emissions from Copper Complexes via Multichannel Balanced Intersystem Crossing: Toward 100% Quantum Efficiencies

Abstract Luminescent materials have important applications in biology, medicine, catalysis, energy, information technology, and so on. However, to suppress quenching and improve efficiencies, how to balance singlet and triplet radiations for efficient dual emission composed of equalized thermally activated delayed fluorescence (TADF) and phosphorescence remains a formidable challenge. Here, we report that based on a rigid skeleton of triphosphine CuI complex, modification with carbazole donors results in high‐lying ligand‐centered charge transfer states, which provide additional channels for accurately optimizing the singlet‐triplet ratios. We achieve equalized dual emissions containing 53% TADF and 47% phosphorescence, ∼100% photo‐ and electro‐luminescence quantum efficiencies and record‐high external quantum efficiencies of ∼30% for pure‐yellow organic light‐emitting diodes. Photophysical and exciton kinetics analyses indicate the incorporation of high‐lying ligand‐centered triplet states into dual‐emissive electroluminescence is based on energy‐level matching with the first triplet states of host matrixes.