Coordination-Induced Thermally Activated Delayed Fluorescence: From Non-TADF Donor–Acceptor-Type Ligand to TADF-Active Ag-Based Complexes

Herein, we present a new strategy in which highly emissive thermally activated delayed fluorescence (TADF) materials can be obtained from modifying or tuning a non-TADF donor (D)–acceptor (A)-type organic molecule via coordination of the metal ionic fragment. Theoretical calculation and photophysical properties reveal that the D–A-type free ligand emits both weak fluorescence and dual room-temperature phosphorescence, whereas the two Ag(I) complexes display efficient blue TADF, exhibiting photoluminescence quantum yields nearly 100% in films with short decay lifetimes (τ ≈ 6 μs). This is attributed to the four optimized parameters induced by Ag(I) coordination: (1) narrow singlet (S1)–triplet (T1) energy gaps (ΔEST). (2) T1 states have a hybrid local excitation and charge transfer (CT) character, and S1 states have a predominant CT character. Both the parameters facilitate reverse intersystem crossing. (3) Radiative rate constant (kr(S1→S0)) is increased. (4) Molecular rigidity is strengthened. For the first time, this work shows a powerful method to design efficient ligand-centered TADF in Ag(I) complexes based on the conventional D–A-type molecule, which significantly enriches the chemical space for the development of TADF materials.