Tuning the Electronic Nature of Aggregation-Induced Emission Luminogens with Enhanced Hole-Transporting Property

Abstract

Triphenylamine (TPA) is a well-known hole-transporting material but suffers aggregation-caused emission quenching in the solid state. Tetraphenylethene (TPE), on the other hand, is an archetypal luminogen that shows the phenomenon of aggregation-induced emission (AIE). In this work, TPA is attached to the TPE core as peripheral group to generate new AIE luminogens with enhanced hole-transporting property. The TPA-TPE adducts, named 1-[4′-(diphenylamino)biphenyl-4-yl]-1,2,2-triphenylethene (TPATPE) and 1,2-bis[4′-(diphenylamino)biphenyl-4-yl]-1,2-diphenylethene (2TPATPE) are synthesized in satisfactory yields by Suzuki coupling of 4-(diphenylamino)phenylboronic acid with 1-(4-bromophenyl)-1,2,2-triphenylethene and 1,2-bis(4-bromophenyl)-1,2-diphenylethene, respectively. Whereas the hybrid molecules are practically nonluminescent in the solution state, their aggregates in poor solvents and thin films emit intensely with fluorescence quantum yields up to 100%. Both TPATPE and 2TPATPE are thermally and morphologically stable, showing high thermal-degradation (T d up to 430 °C) and glass transition (T g = 119 °C) temperatures. Multilayer electroluminescence (EL) devices are constructed, which emit sky blue and green EL with maximum luminance of 32230 cd/m2 and current efficiency up to 13.0 cd/A. The devices without hole-transporting layers (HTL) show performances comparable to or better than those with HTL, presumably because of the high hole mobility of TPATPE and 2TPATPE coupled with the matching of their energy levels with the anode.

A stimuli-responsive double-stranded digold(i) helicate

“…Intermolecular π···π interactions, 20 however, can have dramatic impact on the solid-state luminescence properties and can lead to red shifts in the emission spectra. 7 In I B crystal, the [Au 2 L 2 ] 2+ helicates are packed into head-to-tail fashion to form columnar stacks (Fig.…”

“…36 Eisenberg and co-workers have found that a weakly emissive thiouracil (tuH) 15 gold(I) complex, [Au 2 (μ-tuH)(μ-dppm)](CF 3 CO 2 ) after gentle crushing exhibits intense blue luminescence as a result of a molecular structure modification occurred upon a solid-state chemical reaction (release of CF 3 CO 2 H). 40 However, up to now, only two gold(I) complexes that exhibit reversible 20 mechanochromic luminescence have been reported. 42, 43 Ito and Sawamura reported the [(F 5 C 6 Au) 2 (μ-1,4-CNC 6 H 4 )] complex that shows a change in its luminescence colour from blue to yellowgreen upon grinding and subsequent reversion to its original emission colour upon solvent treatment.…”

Aggregation-induced delayed fluorescence from phenothiazine-containing donor–acceptor molecules for high-efficiency non-doped organic light-emitting diodes

“…This AIE phenomenon can be explained by the restriction of non-radiative vibrational relaxation processes in the aggregated solid state. Representative examples of AIE-active fluorophores include siloles, [6][7][8][9] cyanostilbenes, [10][11][12] o-carborane derivatives [13][14][15][16][17] and tetraphenylethenes [18][19][20][21][22][23] . Some of these fluorophores have proved useful as non-doped emission layers in fluorescent OLEDs.…”

“…Some of these fluorophores have proved useful as non-doped emission layers in fluorescent OLEDs. [19][20][21][22][23] However, these OLEDs can only utilize singlet excitons for electroluminescence (EL) and the resulting internal EL quantum efficiency (η int ) is limited to 25% because of the inherent spin-statistical limitation of electrical excitation, which generates radiative singlet excitons and non-radiative triplet excitons in a 1:3 ratio. 24 Recent research efforts in our group 25 and others [26][27][28][29][30] have focused on exploring AIE-active materials that simultaneously exhibit thermally activated delayed florescence [31][32][33][34][35][36][37][38][39] to harvest triplet excitons for EL via efficient reverse intersystem crossing.…”

“…Some of these fluorophores have proved useful as non-doped emission layers in fluorescent OLEDs. [19][20][21][22][23] However, these OLEDs can only utilize singlet excitons for electroluminescence (EL) and the resulting internal EL quantum efficiency (η int ) is limited to 25% because of the inherent spin-statistical limitation of electrical excitation, which …”