As eries of donor-acceptor-donor triazine-based molecules with thermally activated delayedf luorescence (TADF) properties were synthesized to obtain highly efficient blue-emitting OLEDs with non-doped emitting layers (EMLs). The targeted molecules use at riazinec ore as the electron acceptor,a nd ab enzene ring as the conjugated linker with different electrond onors to alternate the energy level of the HOMO to further tune the emission color.T he introduction of long alkyl chains on the triazine core inhibits the unwanted intermolecular D-D/A-A-type p-p interactions, resulting in the intermolecularD -A charget ransfer.T he weak aggregation-causedq uenching (ACQ) effectc aused by the sup-pressed intermolecular D-D/A-A-type p-p interaction further enhancest he emission.T he crowded molecular structure allows the electrond onor and acceptort ob en early orthogonal, thereby reducing the energy gap between triplet and singlet excited states (DE ST ). As ar esult, blue-emitting devices with TH-2DMAC and TH-2DPAC non-doped EMLs showed satisfactory efficiencies of 12.8 %a nd 15.8 %, respectively,w hichi so ne of the highest external quantum efficiency (EQEs) reported for blue TADF emitters( l peak < 475 nm), demonstratingt hat our tailored molecular designsare promising strategies to endow OLEDs with excellent electroluminescent performances.
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