Chiral boron/nitrogen doped multiple resonance thermally activated delayed fluorescence (MR‐TADF) emitters are promising for highly efficient and color‐pure circularly polarized organic light‐emitting diodes (CP‐OLEDs). Herein, we report two pairs of MR‐TADF materials (Czp‐tBuCzB, Czp‐POAB) based on planar chiral paracyclophane with photoluminescence quantum yields of up to 98 %. The enantiomers showed symmetric circularly polarized photoluminescence spectra with dissymmetry factors |gPL| of up to 1.6×10−3 in doped films. Meanwhile, the sky‐blue CP‐OLEDs with (R/S)‐Czp‐tBuCzB showed an external quantum efficiency of 32.1 % with the narrowest full‐width at half‐maximum of 24 nm among the reported CP‐OLEDs, while the devices with (R/S)‐Czp‐POAB displayed the first nearly pure green CP electroluminescence with |gEL| factors at the 10−3 level. These results demonstrate the incorporation of planar chirality into MR‐TADF emitter is a reliable strategy for constructing of efficient CP‐OLEDs.
The integration of carbazole (Cz) unit and emissive iridium(III) complexes is a wise choice to facilitate hole injection/transport, charge balance, and achieve phosphorescent emitters for high‐performance organic light‐emitting diodes (OLEDs). Herein, three efficient Cz‐based Ir(III) complexes are synthesized and applied for OLEDs. The introduction of trifluoromethyl and trimethylsilyl units alter the photoelectric properties of these complexes, achieving photoluminescence (PL) from yellow (559 nm) to orange‐red (600 nm) with high PL quantum yields between 75% and 93% and short excited state lifetimes between 1.09 and 1.90 µs in doped thin films. Multilayer OLEDs using the three emitters exhibit highest current efficiency as high as 100.4 cd A−1 and maximum external quantum efficiency (EQEmax) up to 32.2% with very low efficiency roll‐off. Even at high brightness of 5000 and 10 000 cd m−2, the device D3 still can maintain the EQE at 28.2% and 27.9%, respectively. These results indicate that these complexes incorporating Cz units are potential substituents for efficient OLEDs.
Herein, we report the structures of chiral‐at‐cage carborane derivatives bearing carbazole chromophores that emit circularly polarized luminescence (CPL) and aggregation‐induced electrochemiluminescence (AIECL). By adjusting the substituent positions on the carborane derivatives, two chiral luminescent molecules, Cb1 and Cb2, with different properties were obtained. The photoluminescence dissymmetry factors |gPL| of both (R/S)‐Cb1 and (R/S)‐Cb2 enantiomers in neat films were as high as 6.24×10−3 and 7.38×10−3, respectively. Cb1 showed a deep blue emission peak at 434 nm in n‐pentane. Interestingly, distinct fluorescence and CPL spectra were observed in solvents of different polarities due to the twisted intramolecular charge transfer effect, suggesting its potential use in solvent recognition. Meanwhile, Cb2 exhibited good AIECL property, excellent ECL stability and could be used for determining dopamine concentrations, suggesting its potential applications in biology and diagnosis.
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