Spiro-Based Thermally Activated Delayed Fluorescence Emitters with Reduced Nonradiative Decay for High-Quantum-Efficiency, Low-Roll-Off, Organic Light-Emitting Diodes

Herein, we report the use of spiro-configured fluorene-xanthene scaffolds as a novel, promising, and effective strategy in thermally activated delayed fluorescence (TADF) emitter design to attain high photoluminescence quantum yields (ΦPL), short luminescence lifetime, external efficiency (EQE), minimum roll-off characteristics organic light-emitting diodes (OLEDs). The optoelectronic electroluminescence properties SFX (spiro-(fluorene-9,9'-xanthene))-based emitters (SFX-PO-DPA, SFX-PO-DPA-Me, SFX-PO-DPA-OMe) were investigated both theoretically experimentally. All three exhibited sky blue green emission enabled by Herzberg-Teller mechanism excited state. They possess excited-state lifetimes (<10 μs), (ΦPL ∼ 70%), small singlet-triplet splitting energies (ΔEST < 0.10 eV) doped films an mCP host matrix. OLEDs showed some highest EQEs using spiro-containing where maximum efficiencies (EQEmax) 11 16% obtained for devices SFX-PO-DPA SFX-PO-DPA-OMe, respectively. Further, record EQEmax 23% spiro-based coupled with low (19% at 100 cd m-2) was attained SFX-PO-DPA-Me.