Through Space Charge Transfer for Efficient Sky‐Blue Thermally Activated Delayed Fluorescence (TADF) Emitter with Unconjugated Connection

Abstract Through‐space charge transfer, which exists in nonconjugation linker based thermally activated delayed fluorescence (TADF) materials, excites chemists to explore more possibilities in organic light‐emitting diodes (OLEDs). Herein, an sp 3 ‐hybrid carbon‐centered donor–σ–acceptor type chromophore, QAFCN, is tentatively developed by exploring bi‐acridine based electron‐donor, i.e., 5,5‐dimethyl‐5,9‐dihydroquinolino[3,2,1‐de]acridine (QA). It is interesting to find that the QA moiety shows downshift in highest occupied molecular orbital because of its deformed geometry, which makes it qualified for sky‐blue electroluminescence emission. Together with the blue‐shift, enhanced photoluminescence quantum yield and faster reverse intersystem crossing rate are also observed in QAFCN, which can be attributed to the close through‐space distance between donor/acceptor. As compared to the ACRFLCN without these special features, QAFCN has obvious TADF property and achieves efficient OLEDs of ≈18% external quantum efficiency.