Search

A multidentate tetrazole molecule based on a TPE core, tetrakis[4-(1H-tetrazol-5-yl)phenyl]ethylene (H4ttpe) with combined advantages of two functional groups, was synthesized by cycloaddition reaction of the corresponding organic benzonitrile derivative and azide salt. Coordination self-assembly of the in situ formed aggregation-induced emission polytetrazole luminogen with cadmium(II) ion produces an unprecedented tetrazolyl-TPE-based microporous cationic metal–organic framework (MOF) with an unusual (4,5,8T14)-connected net of {[Cd4(H4ttpe)2Cl5]·(N3)3}, in which the H4ttpe serves as the first undeprotonated tetrazole ligand of octa-coordinating bridging mode. We investigate, for the first time, the utilization of the luminescent MOF containing a TPE core decorated with tetrazolyl terminals for explosive detection based on the change in fluorescence intensity, which shows high selectivity and efficiency in fluorescence quenching toward TNP detection in water solution.

Cross-linking is demonstrated to be an effective strategy to resolve the interface erosion problem facing solution process technique for large area commercial applications of organic electronics. However, most of the reported cross-linkable materials require a high temperature of over 150 °C, which is detrimental to device performance. In this study, an in situ cross-linking protocol is proposed based on a triphenylamine/carbazole core linked with a hexyl chain and styryl moiety, and a low cross-linking temperature down to 120 °C is achieved for the first time. The resultant thermally cross-linkable hole transportation molecules of TPA-VBCz and HTPA-VBCz possess high triplet energy levels of around 3.0 eV and high decomposition temperatures over 410 °C. The solution-processed hole transportation layer (HTL) is cured at 120 °C in 30 min to finish the cross-linking net structure. Applications of this HTL in solution-processed multilayer thermally delayed fluorescent green OLEDs are explored with significantly improved current efficiency up to 78.3 cd A–1and external quantum efficiency of 24.6%.

In this paper, a pair of rigid chiral D-A type enantiomers (S-/R-2) incorporating the pyrene moiety as the donor and 1,8-naphthalimide as the acceptor was chosen as circularly polarized electroluminescence (CP-EL) emitters. This kind of chiral emitter exhibits good thermal stability (Td= 389 °C, Tg= 112 °C), high fluorescence quantum yields (46.4/42.4%), and CPL-active materials (glum= +1.46 × 10–3/–1.40 × 10–3for S-/R-2) in the solid state. The nondoped OLEDs with the structure of ITO/PEDOT:PSS (25 nm)/S-2 or R-2 (35 nm)/TPBi (35 nm)/Ca (10 nm)/Ag (100 nm) show turn-on voltages of 4.4 and 4.2 V, maximum luminance values of 19575 and 18411 cd m–2, maximum current efficiencies of 2.8 and 3.2 cd A–1, and high green brightness CP-EL signals with gELvalues of +2.15 × 10–3and −2.23 × 10–3for S-2 and R-2, respectively.

A pair of chiral binaphthyl enantiomers (S-/R-6) incorporating a tetraphenylethene (TPE) moiety as an aggregation-induced emission (AIE) active group exhibits bright yellow circularly polarized electroluminescence (CP-EL) emission with a remarkable gELvalue, low turn-on voltage, and high brightness in the nondoped CP organic light emitting diodes (CP-OLEDs). This work provides a new strategy to develop doping-free CP-OLED materials.

The use of mixed hosts has been demonstrated to be an effective way to improve the efficiency of phosphorescent organic light-emitting diodes (PhOLEDs). In this study, a macrospirocyclic oligomer (Cz-F)4based on carbazole and fluorene is synthesized as a solution-processable matrix host material for blue PhOLEDs. The oligomer exhibits a high triplet level, good film-forming ability, solution processability, and doping compatibility. As a result, a blue solution-processed PhOLED based on a (Cz-F)4/TAPC [1,1-bis((di-4-tolylamino) phenyl) cyclohexane] mixed host achieves a maximum current efficiency of 18.8 cd/A with a turn-on voltage of 3.3 V. When a ternary mixed-host system composed of (Cz-F)4, TAPC, and OXD-7 [1,3-bis(5-(4-(tert-butyl)phenyl)-1,3,4-oxadiazol-2-yl)benzene] is employed, the device exhibits a low turn-on voltage of 2.8 V, and the driving voltages are only 3.8–4.6 V at the practical luminance of 100–1000 cd/m2. Even at 5000 and 10 000 cd/m2, the driving voltages are only 5.7 and 6.6 V, respectively. The current efficiency roll-off is only 12% from 100 to 5000 cd/m2. This study demonstrates that monodisperse oligomers can serve a matrix host for highly efficient blue solution-processed PhOLEDs with low turn-on voltage, low driving voltage, and suppressed efficiency roll-off.

Three solution-processable exciplex-type host materials were successfully designed and characterized by equal molar blending hole transporting molecules with a newly synthesized electron transporting material, which possesses high thermal stability and good film-forming ability through a spin-coating technique. The excited-state dynamics and the structure–property relationships were systematically investigated. By gradually deepening the highest occupied molecular orbital (HOMO) level of electron-donating components, the triplet energy of exciplex hosts were increased from 2.64 to 3.10 eV. Low temperature phosphorescence spectra demonstrated that the excessively high triplet energy of exciplex would induce a serious energy leakage from the complex state to the constituting molecule. Furthermore, the low energy electromer state, which only exists under the electroexcitation, was found as another possible channel for energy loss in exciplex-based phosphorescent organic light-emitting diodes (OLEDs). In particular, as quenching of the exciplex-state and the triplet exciton were largely eliminated, solution-processed blue phosphorescence OLEDs using the exciplex-type host achieved an extremely low turn-on voltage of 2.7 eV and record-high power efficiency of 22.5 lm W–1, which were among the highest values in the devices with identical structure.

Three bipolar hosts, namely TPA-DAF, TPA-DAF2, and TPA-DAF3, comprising an electron-donating triphenylamine (TPA) group and electron-accepting 4,5-diazafluorene (DAF) units are investigated for phosphorescent organic light-emitting diodes (PhOLEDs). Given the nonplanar structure of the sp3-hybridized C9 atom in DAF unit, these molecules have a highly nonplanar configuration, good film-forming property, and high triplet energy (ET) of 2.88–2.89 eV. Among them, TPA-DAF shows more balanced carrier injecting/transporting ability, suitable highest occupied molecular orbital (MO) energy level and higher current density, and therefore TPA-DAF-based devices exhibit the best performances, having an extremely slight efficiency roll-off with current efficiency of 20.0 cd/A at 973 cd/m2, 19.5 cd/A at 5586 cd/m2, and 17.6 cd/A at 9310 cd/m2for blue PhOLEDs; 23.5 cd/A at 1059 cd/m2and 15.3 cd/A at 8850 cd/m2for green PhOLEDs; and 12.2 cd/A at 1526 cd/m2, 10.5 cd/A at 5995 cd/m2, and 9.2 cd/A at 8882 cd/m2for red PhOLEDs, respectively. The results also provide a direct proof for the influence of charge balance on the device performance.

Taking all crosssectional sizes as design variables, the paper presents a method that transforms the original optimal design model of frame structures to standard signomial geometric programming SGP through the generalized polynomial approach. The SGP is then solved by the condensationally based cuttingplane method. To decrease the scale of the problem, the strength constraints are changed to size constraints by the fully stressed design method in the transformation. Several numerical examples are presented, and it is proved that this method is successful.

Tetraphenylethene (TPE) is a popular luminogen characterized by aggregation-induced emission and has been widely used to construct solid-state emissive materials. In this work, two thermally stable polymers (P1and P2) consisting of TPE conjugated to the 2,7-positions of fluorene and carbazole, respectively, are synthesized and characterized. Both polymers are weakly fluorescent in solutions but show greatly enhanced emission as the aggregate formation, presenting an aggregation-enhanced emission feature. Two kinds of polymer light-emitting diodes are fabricated utilizing P1and P2as emitters (EML) (device I: ITO/PEDOT:PSS (45 nm)/PVK:EML (1:1 wt%, 55 nm)/TPBI (38 nm)/Ca:Ag; device II: ITO/PEDOT:PSS (45 nm)/PVK:OXD-7:EML (3:1:3 wt%, 55 nm)/TPBI (38 nm)/Ca:Ag). The device II of P2shows the best performances, affording a maximum luminance of 6500 cd/m2and a high peak efficiency of 2.11 cd/A.

Diarylethene derivatives are a class of fascinating photochromic materials because of their open and closed isomers with different absorption spectra and many other characteristics. To reveal the detailed structure and optoelectronic properties as well as the effect of metal centres and substituents on them, a systematic study on a series of diarylethene derivatives and their Re(I), Pt(II), and Ir(III) complexes was performed via theoretical calculation. The optimized geometries, electronic properties, frontier molecular orbitals, ionization potentials, electron affinities, reorganization energies, and absorption spectra for both of their open- and closed-isomers have been calculated and analyzed. Metal-coordination and substituents exhibit great influence on the photophysical, charge-injection and -transporting characteristics. In addition, the binding of F-with the boron atom of dimesitylboryl group through Lewis acid/base interactions also induces great changes of structural, photophysical and electronic properties for these diarylethene derivatives, and consequently the compound with the substituent of dimesitylboryl group can be used as selective near-infrared phosphorescent F-probe.Diarylethene derivatives are a class of fascinating photochromic materials because of their open and closed isomers with different absorption spectra and many other characteristics. To reveal the detailed structure and optoelectronic properties as well as the effect of metal centres and substituents on them, a systematic study on a series of diarylethene derivatives and their Re(I), Pt(II), and Ir(III) complexes was performed via theoretical calculation. The optimized geometries, electronic properties, frontier molecular orbitals, ionization potentials, electron affinities, reorganization energies, and absorption spectra for both of their open- and closed-isomers have been calculated and analyzed. Metal-coordination and substituents exhibit great influence on the photophysical, charge-injection and -transporting characteristics. In addition, the binding of F-with the boron atom of dimesitylboryl group through Lewis acid/base interactions also induces great changes of structural, photophysical and electronic properties for these diarylethene derivatives, and consequently the compound with the substituent of dimesitylboryl group can be used as selective near-infrared phosphorescent F-probe.

With the aim to develop new tetraphenylethylene (TPE)‐based conjugated hyperbranched polymer, TPE units, one famous aggregation‐induced emission (AIE) active group, are utilized to construct hyperbranched polymers with three other aromatic blocks, through an “A2+B4” approach by using one‐pot Suzuki polycondensation reaction. These three hyperbranched polymers exhibit interesting AIEE behavior and act as explosive chemsensors with high sensitivity both in the nanoparticles and solid states. This is the first report of the AIE activity of the TPE‐based conjugated hyperbranched polymers. Their corresponding PLED devices also demonstrate good performance.

A new donor–acceptor type polyfluorene derivative, poly[9,9‐dioctyl‐2,7‐fluorene‐alt‐(4,7‐bis(2′‐thienyl)‐2‐octyl‐2,1,3‐benzotriazole)] (PFDTBTz), is synthesized by a Suzuki cross‐coupling polymerization reaction. The optical, electrochemical, photovoltaic, and electroluminescence properties of PFDTBTz are investigated in detail. The maximum power conversion efficiency (PCE) of the PSCs based on PFDTBTz/PC71BM (1:2 w/w) reaches 2.1% with a short circuit current density (Jsc) of 5.73 mA · cm−2, an open circuit voltage (Voc) of 0.84 V, and a fill factor (FF) of 0.44 under AM 1.5G, 100 mW · cm−2illumination. Polymer light‐emitting diodes (PLEDs) are fabricated in an ITO/PEDOT:PSS (30 nm)/PFDTBTz (60 nm)/BAlq (40 nm)/Cs2CO3:Ag configuration and light emission is observed at a voltage greater than 8.0 V. The EL device shows almost pure red and the efficiency is very stable when the current density is increased, making it useful for commercial applications.

A new series of full hydrocarbons, namely 4,4′‐(9,9′‐(1,3‐phenylene)bis(9H‐fluorene‐9,9‐diyl))bis(N,N‐diphenylaniline) (DTPAFB), N,N′‐(4,4′‐(9,9′‐(1,3‐phenylene)bis(9H‐fluorene‐9,9‐diyl))bis(4,1‐phenylene))bis(N‐phenylnaphthalen‐1‐amine) (DNPAFB), 1,3‐bis(9‐(4‐(9H‐carbazol‐9‐yl)phenyl)‐9H‐fluoren‐9‐yl)benzene, and 1,3‐bis(9‐(4‐(3,6‐di‐tert‐butyl‐9H‐carbazol‐9‐yl)phenyl)‐9H‐fluoren‐9‐yl)benzene, featuring a highly twisted tetrahedral conformation, are designed and synthesized. Organic light‐emitting diodes (OLEDs) comprising DNPAFB and DTPAFB as hole transporting layers and tris(quinolin‐8‐yloxy)aluminum as an emitter are made either by vacuum deposition or by solution processing, and show much higher maximum efficiencies than the commonly used N,N′‐di(naphthalen‐1‐yl)‐N,N′‐diphenylbiphenyl‐4,4′‐diamine device (3.6 cd A−1) of 7.0 cd A−1and 6.9 cd A−1, respectively. In addition, the solution processed blue phosphorescent OLEDs employing the synthesized materials as hosts and iridium (III) bis[(4,6‐di‐fluorophenyl)‐pyridinato‐N, C2] picolinate (FIrpic) phosphor as an emitter present exciting results. For example, the DTPAFB device exhibits a brightness of 47 902 cd m−2, a maximum luminescent efficiency of 24.3 cd A−1, and a power efficiency of 13.0 lm W−1. These results show that the devices are among the best solution processable blue phosphorescent OLEDs based on small molecules. Moreover, a new approach to constructing solution processable small molecules is proposed based on rigid and bulky fluorene and carbazole moieties combined in a highly twisted configuration, resulting in excellent solubility as well as chemical miscibility, without the need to introduce any solubilizing group such as an alkyl or alkoxy chain.

A new linear six thiophene‐fused systemof hexathienoacene (HTA) has been synthesized, which has also been compared with pentathienoacene (PTA) in terms of optical, electrochemical, and charge‐transfer properties of organic semiconductors. The highest mobility of 0.06 cm2V−1s−1with a current on/off ratio of 105on n‐octadecyltrichlorosilane (OTS)‐treated SiO2/Si substrates has been achieved.

Asymmetrical heteroacene up to six fused rings, tetraceno[2,3-b]benzo[d]thiophene (TBT), was synthesized facilely and its physicochemical properties and device applications were investigated. Field-effect transistors (FETs) fabricated with TBT as semiconducting layers showed carrier mobility up to 0.13 cm2V−1s−1. The transistors also exhibited a photoeffect and a ratio of photocurrent to dark-current as high as 104was achieved. Density functional theory and FET results demonstrated that, for bent heteroacenes, increasing a benzene ring in conjugation length would not result in higher field-effect mobility, and the FET performance is more influenced by the thin film morphology. All these results suggest that the introduction of heteroatoms provides an efficient route for exploring the chemistry of larger acenes.

A series of novel asymmetrical fused compounds containing the backbone of fluorene[2,3‐b]benzo[d]thiophene (FBT) were effectively synthesized and fully characterized. Single‐crystal X‐ray studies demonstrated that the length of the substituent side chains greatly affects the solid‐state packing of the obtained fused compounds. DFT, photophysical, and electrochemical studies all showed that the FBTs have large band gaps, low‐lying HOMO energy levels, and therefore good stability toward oxidation. Moreover, the substituents strongly influence the fluorescence properties of the resulting FBT derivatives. The di‐n‐hexyl compound exhibits intense fluorescence in solution with the highest quantum yield of up to 91 %. Solution‐processed green phosphorescent organic light‐emitting diodes with the di‐n‐butyl derivative as the host material exhibited a maximum brightness of 14 185 cd m−2and a luminescence efficiency of 12 cd A−1.

High‐performance organic transistor memory elements with donor‐polymer blends as buffer layers are presented. These organic memory transistors have steep flanks of hysteresis with an ON/OFF memory ratio of up to 2 × 104, and a retention time in excess of 24 h. Inexpensive materials such as poly(methyl methacrylate), ferrocene and copper phthalocyanine are used for the device fabrication, providing a convenient approach of producing organic memory transistors at low cost and high efficiency.

Novel blue‐light‐emitting fluorene derivatives 5a–cand 7a–ccontaining bulky and highly emissive groups, namely pyrene, 10‐phenylanthracene‐9‐yl and 10‐(4′‐diphenylaminophenyl)anthracene‐9‐yl groups, as well as hole‐injecting/transporting triarylamines were synthesized. Single crystals of compounds 5a, 5c, 7a, and 7cwere grown and their crystal structures were determined by X‐ray diffraction. The four fluorene derivatives have nonplanar molecular structures, which reduce the intermolecular interaction and the likelihood of molecular aggregation or excimer formation. No unwanted long‐wavelength emission was observed in the photoluminescence (PL) spectra of the 5a–cand 7a–cthin films. Their PL spectra reveal excellent thermal stability after annealing treatment under air and ambient light. All of the six compounds show high fluorescence quantum yields and outstanding thermal stabilities. The 2‐aryl and 2,7‐diaryl substituents at the fluorene molecule have a significant effect on the photophysical properties and the thermal characteristics. The six compounds show almost the same energy levels for the highest occupied molecular orbitals (HOMOs) of about −5.20 eV, which allows effective hole injection. The C2‐ and C7‐aryl substituents play a relatively less‐important role in the HOMO energy levels, which depend mainly on the triphenylamino groups at the C9 position. The molecular orbitals, excitation energy, and emission energy were calculated to explain the real origin of their photophysical characteristics. The HOMOs are mainly localized on the triphenylamino groups at the C9 position, while the lowest unoccupied molecular orbitals (LUMOs) have a significant orbital density at the C2‐ and/or C7‐aryl substituents. Pure‐blue‐light‐emitting diodes based on 2,7‐diaryl‐9,9‐di(triarylamino)fluorenes were fabricated.