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.
Highlights
IntroductionOrganic fluorophores emitting prompt blue fluorescence are required by industry since they are characterized by many advantages including high photoluminescence quantum yield (PLQY), fast fluorescent decays (in ns range, which are of interest for displays and for visible light communications), good blue color purity, chromaticity coordinates which meet the NationalTelevision System Committee requirements, etc. [1,2,3,4]
Organic fluorophores emitting prompt blue fluorescence are required by industry since they are characterized by many advantages including high photoluminescence quantum yield (PLQY), fast fluorescent decays, good blue color purity, chromaticity coordinates which meet the National
Based devices, blue fluorescent emitters are used in commercial organic light‐emitting diodes (OLEDs) of display and lighting technologies [7]
Summary
Organic fluorophores emitting prompt blue fluorescence are required by industry since they are characterized by many advantages including high photoluminescence quantum yield (PLQY), fast fluorescent decays (in ns range, which are of interest for displays and for visible light communications), good blue color purity, chromaticity coordinates which meet the NationalTelevision System Committee requirements, etc. [1,2,3,4]. Based devices, blue fluorescent emitters are used in commercial organic light‐emitting diodes (OLEDs) of display and lighting technologies [7]. Such interest in blue fluorescence is mainly explained by its higher stability under electrical excitation, than that of mentioned blue phosphorescent and TADF emitters, the stability of which is fundamentally limited due to the Molecules 2020, 25, 445; doi:10.3390/molecules25030445 www.mdpi.com/journal/molecules. Materials exhibiting AIE or AIEE phenomena are established as multifunctional materials They are useful for OLEDs and for chemical sensing, for detection of stimuli responses, bio and surface visualizations etc. They are useful for OLEDs and for chemical sensing, for detection of stimuli responses, bio and surface visualizations etc. [16]
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