Towards Blue AIE/AIEE: Synthesis and Applications in OLEDs of Tetra-/Triphenylethenyl Substituted 9,9-Dimethylacridine Derivatives

Abstract

Aiming to design blue fluorescent emitters with high photoluminescence quantum yields in solid-state, nitrogen-containing heteroaromatic 9,9-dimethylacridine was refined by tetraphenylethene and triphenylethene. Six tetra-/triphenylethene-substituted 9,9-dimethylacridines were synthesized by the Buchwald-Hartwig method with relatively high yields. Showing effects of substitution patterns, all emitters demonstrated high fluorescence quantum yields of 26–53% in non-doped films and 52–88% in doped films due to the aggregation induced/enhanced emission (AIE/AIEE) phenomena. In solid-state, the emitters emitted blue (451–481 nm) without doping and deep-blue (438–445 nm) with doping while greenish-yellow emission was detected for two compounds with additionally attached cyano-groups. The ionization potentials of the derivatives were found to be in the relatively wide range of 5.43–5.81 eV since cyano-groups were used in their design. Possible applications of the emitters were demonstrated in non-doped and doped organic light-emitting diodes with up to 2.3 % external quantum efficiencies for simple fluorescent devices. In the best case, deep-blue electroluminescence with chromaticity coordinates of (0.16, 0.10) was close to blue color standard (0.14, 0.08) of the National Television System Committee.

Multifunctional properties of D–A luminophores based on acenaphtopyrido[2,3-b]pyrazine core: photophysics, photochemistry, and efficient solution-processed OLEDs

“…In addition, the aggregate environment is much more rigid than the solution, which can also contribute to the PL blue shift. [63][64][65] We studied the initial THF solutions ( f w = 0%) and the final suspensions ( f w = 90%) using the time-correlated single photon counting (TCSPC) technique to identify the long-lived luminescence components originating from the aggregates (Fig. S30, ESI †).…”

AIEE-active V-shaped fused-biscoumarins: synthesis, photophysical and electroluminescence properties

“…The compounds CC-TPE and CC-TriPE in CH 2 Cl 2 exhibited similar UV-vis absorption spectra with absorption bands at 297, 391 and 464 nm for CC-TPE and 295, 402 and 464 nm for CC-TriPE. The intense absorption bands at 297 nm for CC-TPE and 295 nm for CC-TriPE could be assigned to the pp* transitions of the tetraphenylethylene and triphenylethylene moieties, 21,[40][41][42] and the moderate absorption bands at 391 nm for CC-TPE and 402 nm for CC-TriPE could be ascribed to the pp* transitions of the V-shaped fused-biscoumarin skeletons. 36,37 The strong absorption band at 464 nm of CC-TPE and CC-TriPE could be attributed to the intramolecular charge transfer (ICT) transitions from the tetraphenylethylene and triphenylethylene moieties to the V-shaped fused-biscoumarin cores, 35 respectively.…”

“…Surprisingly, CC-TPE in dichloromethane displayed strong green emission, but in the solid power and thin solid film, CC-TPE showed yellow emission with a swift decrease in the F f , which does not correspond with the AIE characteristics normally exhibited by the compounds containing tetraphenylethene groups. [14][15][16]18,21 From the structures of CC-TPE, CC-TriPE and CC-TPA, CC-TPE and CC-TPA were obtained by linking the tetraphenylethene (TPE) and triphenylamine (TPA) units to the V-shaped fusedbiscoumarin core through the phenyl group of the TPE and TPA units, while CC-TriPE was obtained by directly linking the V-shaped fused-biscoumarin core to the ethylene group of the triphenylethene (TriPE) unit, which could result in a more rigid structure and considerably twisted conformation upon aggregation for CC-TriPE.…”

“…13–18 AIE and AIEE effects can be ascribed to the restricted intramolecular rotation (RIR) and highly twisted molecular conformations in the aggregation that inhibit strong intermolecular π–π stacking interactions, which are advantageous with respect to the highly efficient nondoped OLEDs. 19–23…”

“…[13][14][15][16][17][18] AIE and AIEE effects can be ascribed to the restricted intramolecular rotation (RIR) and highly twisted molecular conformations in the aggregation that inhibit strong intermolecular p-p stacking interactions, which are advantageous with respect to the highly efficient nondoped OLEDs. [19][20][21][22][23] Heterocycle-fused coumarin derivatives with the p-extended conjugation systems possess promising photophysical properties in comparison with the simple coumarin derivatives. [24][25][26][27][28][29][30] Among the heterocycle-fused coumarins, V-shaped fused-biscoumarins have attracted significant attention due to their distinguished properties, such as bathochromic-shift in the emission and excitation wavelengths, colorimetric properties, and larger Stokes shift, [31][32][33][34][35] and the photophysical properties and applications of V-shaped fused-biscoumarins are strongly dependent on the fused coumarin ring systems.…”