Development
of simple chiral materials with tunable circularly polarized photoluminescence
(CPPL) and circularly polarized electroluminescence (CPEL) for efficient
circularly polarized organic light-emitting diodes (CP-OLEDs) is the
key toward future 3D displays. In this study, four pairs of chiral
1,2-diaminocyclohexane-based fluorescence enantiomers were efficiently
prepared with high yields (up to 92%) and enantiomeric excesses (ee
>99%). By the introduction of N-methyl, carbazole,
and diphenylamine-donating groups, these materials showed multicolor
CPPL and CPEL from blue (420 nm) to red (610 nm) with good thermal
and conformational stability. The multilayer CP-OLEDs based on these
enantiomers show high external quantum efficiency of up to 5.5% with
low-efficiency roll-off and microimage circularly polarized electroluminescence
with a dissymmetry factor (g
EL) of up
to −1.4 × 10–3/+1.3 × 10–3. These results push forward the development of future multicolor
circularly polarized electroluminescent materials.
The exploitation of novel fused carbazole/carbonyl emitters is essential to broaden the application of thermally activated delayed fluorescence (TADF) materials for organic light‐emitting diodes (OLEDs). Here, with the aid of the addition and cyclization of the cyano group with the ortho‐carbazole, fused carbazole/carbonyl based TADF emitters are effectively synthesized via this new synthetic strategy. The attachment of ancillary donors including carbazole, diphenylamine, and phenolazine to the fused carbazole/carbonyl skeletons further tunes their emissions from blue to yellow‐green. Particularly, pure‐blue OLEDs incorporating the peripheral carbazole attached emitter exhibit a maximum external quantum efficiency (EQEmax) of 22.3%, with a small full width at half maximum (FWHM) of 48 nm. In addition, the peripheral phenolazine attached yellow‐green emitter shows extremely small singlet−triplet state energy gap (ΔEST) of 0.01 eV, high photoluminescence quantum efficiency of 82.5%, short delayed fluorescence lifetime of 6.2 µs and good OLED performances with an EQEmax of 21.7%, an FWHM of 68 nm and low efficiency roll‐off. These results demonstrate that the new synthetic strategy for fused carbazole/carbonyl molecules provide a valuable reference for the design of high‐efficient TADF emitters.
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