Motivation on Intramolecular Through-Space Charge Transfer for the Realization of Thermally Activated Delayed Fluorescence (TADF)-Thermally Stimulated Delayed Phosphorescence (TSDP) in C^C^N Gold(III) Complexes and Their Applications in Organic Light-Emitting Devices.

Thermally activated delayed fluorescence (TADF) and the very recently established thermally stimulated delayed phosphorescence (TSDP) are two promising approaches for enhancing the performance of organic light-emitting devices (OLEDs). Here, we have developed a new class of through-space charge transfer (TSCT) carbazolylgold(III) C^C^N complexes with unique TADF-TSDP properties by introducing a rigid arylamine on the carbazolyl auxiliary ligand. The highly twisted conformation between the C^C^N and carbazolyl ligands induces strong through-bond ligand-to-ligand charge transfer (TB-LLCT) character in their lowest singlet and triplet excited states, with small singlet-triplet energy gaps for efficient TADF. Moreover, the close spatial proximity between the cyclometalating ligand and the lateral arylamine enables appreciable intramolecular through-space electronic coupling that allows the generation of relatively low-lying triplet through-space ligand-to-ligand charge transfer (TS-LLCT) excited states. The TADF-TSDP properties are verified by temperature-dependent emission, lifetimes, and ultrafast transient absorption studies. Interestingly, through better alignment with extended planarity and the strengthening of the electron-donating ability of the lateral arylamine, the enhanced through-space electronic coupling can effectively perturb the energies of TBCT, TSCT, and intraligand (IL) excited states and thus manipulates the TSDP efficiency. Orange-emitting vacuum-deposited OLEDs made with these gold(III) complexes demonstrate respectable maximum external quantum efficiencies of >10% and long operational half-lifetimes of up to 65,314 h at a luminance of 100 cd m. This work not only demonstrates the realization of interesting TADF-TSDP and TSCT properties in the gold(III) C^C^N cyclometalated system but also enriches the diversity of molecular design for high-performance TSDP and TSCT emitters.