Cyclic Array of Twisted Donor–Acceptor Conjugates Leading to Deep Blue Thermally Activated Delayed Fluorescence

Achieving thermally activated delayed fluorescence (TADF) from covalently assembled multiple donor–acceptor (D-A) units is challenging due to complex design issues. Here, we use a cyclic multiple donor–acceptor (CPCQ) design approach that includes four nonconjugated TADF active D-A units. Spectroscopic analysis revealed that CPCQ emits deep blue TADF (430 nm) with (a) a high photoluminescence quantum yield (PLQY, 78–80%), (b) a high reverse intersystem crossing rate (kRISC = 2.68 × 107 s–1), and (c) a low singlet–triplet energy gap (ΔEST = 0.13 eV) compared to the parent D-A conjugate. The CPCQ blend (1.0 wt%) also shows blue TADF with a PLQY of 63%. Quantum studies reveal that this strategy enables through-space charge transfer that lowers ΔEST and boosts local triplet densitymissing in PCQdriving faster, more efficient RISC in CPCQ. This finding holds great promise for new directions for designing energy-efficient TADF emitters.