Dinuclear Ag(I) Complex Designed for Highly Efficient Thermally Activated Delayed Fluorescence

The dinuclear Ag(I) complex has been designed to show thermally activated delayed fluorescence (TADF) of high efficiency. Strongly electron-donating terminal ligands are introduced to destabilize the d orbitals of the Ag+ ions. Consequently, the orbitals distinctly contribute to the HOMO, whereas the LUMO is localized on the bridging ligand. This ensures charge transfer character of the lowest excited singlet S-1 and triplet T-1 states. Accordingly, a small energy gap Delta E(S-1-T-1) is obtained, being essential for TADF behavior. Photophysical investigations show that at ambient temperature the complex exhibits TADF reaching a quantum yield of Phi(PL) = 70% with the decay time of only tau = 1.9 mu s, manifesting one of the fastest TADF decays observed so far. Such an outstanding TADF efficiency is based on a small value of Delta E(S-1-T-1) = 480 cm(-1) combined with a large transition rate of k(S-1 -> S-0) = 2.2 X 10(7) s(-1).