Two pyrene-functionalized oligofluorenes (TPA-PyF₃ and CBP-PyF₃) are prepared using the condensation reaction by the Friedel–Crafts procedure. In the produced oligomers, the triphenylamine or N,N′-dicarbazolyl-4,4′-biphenyl core serves as a spacer bearing spiro-linked fluorene moieties to form a multi-H shaped structure. This specific structure efficiently retards the crystallization tendency of the pyrene groups, and gives the materials completely amorphous morphological structure and film forming ability. Solution-processed OLEDs with the structure of ITO/PEDOT:PSS (25 nm)/TPA-PyF₃ or CBP-PyF₃ (40 nm)/TPBI (35 nm)/Ca (10 nm)/Ag (100 nm) show low turn-on voltages of 3.6 V, and the maximum external quantum efficiencies reach 1.78% and 2.07% for TPA-PyF₃ and CBP-PyF_3, respectively. Moreover, both devices exhibit stable deep-blue light emission with Commission International de I'Eclairage (CIE) coordinates of around (0.16, 0.09) at the brightness of 100–1000 cd m⁻². © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 795–801

Due to the advantages of good scalability, flexibility, low cost, ease of processing, 3D-stacking capability, and large capacity for data storage, polymer-based resistive memories have been a promising alternative or supplementary devices to conventional inorganic semiconductor-based memory technology, and attracted significant scientific interest as a new and promising research field. In this review, we first introduced the general characteristics of the device structures and fabrication, memory effects, switching mechanisms, and effects of electrodes on memory properties associated with polymer-based resistive memory devices. Subsequently, the research progress concerning the use of single polymers or polymer composites as active materials for resistive memory devices has been summarized and discussed. In particular, we consider a rational approach to their design and discuss how to realize the excellent memory devices and understand the memory mechanisms. Finally, the current challenges and several possible future research directions in this field have also been discussed.

A selective phosphorescent biothiols probe is synthesized based on Ir(III) complex 1, which has 2,2′-biquinoline as the N^N ligand for realizing the satisfied two-photon absorption cross-section and two-functionalized 2-phenylpyridine ligands with an α,β-unsaturated ketone moiety as the thiol reaction site. The one- and two-photon optical properties of 1 are investigated through UV–vis absorption spectrum and photoluminescence spectrum. This Ir(III) complex can act as an excellent one- and two-photon excited “OFF–ON” phosphorescent probe for biothiols based on the 1,4-addition of biothiol to α,β-unsaturated ketones. Moreover, one- and two-photon-induced luminescent imagings of biothiols in living cells are also realized. Furthermore, the experiments of time-resolved photoluminescence technique and fluorescence lifetime imaging microscopy demonstrate that 1 is able to detect biothiols in the presence of strong background fluorescence. In addition, probe 1 is adsorbed into the shell of mesoporous silica nanoparticles with core–shell structure to form a nanoprobe, which can realize the ratiometric detection of biothiols in absolute water solution and living cells based on two phosphorescent signals.

The application of a time-resolved photoluminescence technique and fluorescence lifetime imaging microscopy for biosensing and bioimaging based on phosphorescent conjugated polyelectrolytes (PCPEs) containing Ir(III) complexes and polyfluorene units is reported. The specially designed PCPEs form 50 nm nanoparticles with blue fluorescence in aqueous solutions. Electrostatic interaction between the nanoparticles and heparin improves the energy transfer between the polyfluorene units to Ir(III) complex, which lights up the red signal for naked-eye sensing. Good selectivity has been demonstrated for heparin sensing in aqueous solution and serum with quantification ranges of 0–70 μM and 0–5 μM, respectively. The signal-to-noise ratio can be further improved through time-resolved emission spectra, especially when the detection is conducted in complicated environment, e.g., in the presence of fluorescent dyes. In addition to heparin sensing, the PCPEs have also been used for specific labeling of live KB cell membrane with high contrast using both confocal fluorescent cellular imaging and fluorescence lifetime imaging microscopies. This study provides a new perspective for designing promising CPEs for biosensing and bioimaging applications.

Homocysteine (Hcy) and cysteine (Cys) are two important kinds of amino acids in human bodies. Herein, we synthesized an iridium(III) complex-functionalized poly(N-isopropylacrylamide) and its hydrogel, which could be used as the excellent phosphorescent bioprobe for sensing Hcy and Cys. Their detection can be realized in aqueous system through the variations in absorption and photoluminescence spectra. Furthermore, living cell imaging experiments demonstrate that the phosphorescent bioprobe is membrane permeable and can monitor the changes of Hcy and Cys within living cells. In addition, the probe is also thermoresponsive, and its photoluminescence intensified with increasing temperature. These results suggests that this bioprobe has promising application in biomedical fields.

In this paper, recent progress in polymer white light-emitting materials and devices published until April 2012 was reviewed according to the kinds of the materials and devices. The polymer light-emitting materials were reviewed by the classification of small-molecule-doped polymer type, polymer blend type, polymer doped small molecule type, molecule-dispersed polymer type, dye-terminated polymer type, and excimer white EL polymer type. The polymer light-emitting devices were reviewed by the classification of fabricating PWLED through the multilayer device and improving efficiency through the multilayer device. The relationship between the structures of materials or devices and properties was the main content during review. At last, some scientific problems and developing trends on PWLED are discussed.

The purposeful modulation of the optoelectronic properties was realised on the basis of a series of the large, conjugated, phosphine oxide hosts 9,9-bis-{4′-[2-(diphenylphosphinoyl)phenoxy]biphenyl-4-yl}-9H-fluorene (DDPESPOF), 9,9-bis-{3′-(diphenylphosphinoyl)-4′-[2-(diphenylphosphinoyl)phenoxy]biphenyl-4-yl}-9H-fluorene (DDPEPOF), 9-[4′-(9-{4′-[2-(diphenylphosphoryl)phenoxy]biphenyl-4-yl}-9H-fluoren-9-yl)biphenyl-4-yl]-9H-carbazole (DPESPOFPhCz) and 9-[4′-(9-{3′-(diphenylphosphoryl)-4′-[2-(diphenylphosphoryl)phenoxy]biphenyl-4-yl}-9H-fluoren-9-yl)biphenyl-4-yl]-9H-carbazole (DPEPOFPhCz). The last two are quaternary with fluorenyls as linking bridges, diphenylphosphine oxide (DPPO) moieties as electron acceptors and diphenylethers and carbazolyls as two different kinds of electron donors. Owing to the fine-organised molecular structures and the mixed indirect and multi-insulating linkages, all of these hosts achieve the same first triplet energy levels (T₁) of 2.86 eV for exothermic energy transfer to phosphorescent dopants. The first singlet energy levels (S₁) and the carrier injection/transportation ability of the hosts were accurately modulated, so that DPESPOFPhCz and DPEPOFPhCz revealed extremely similar optoelectronic properties. However, the T₁ state of the former is localised on fluorenyl, whereas the carbazolyl mainly contributes to the T₁ state of the latter. A lower driving voltages and much higher efficiencies of the devices based on DPESPOFPhCz indicated that the chromophore-localised T₁ state can suppress the quenching effects through realising independent contributions from the different functional groups to the optoelectronic properties and the embedding and protecting effect on the T₁ states by peripheral carrier transporting groups.

Biothiols, such as cysteine (Cys) and homocysteine (Hcy), play very crucial roles in biological systems. Abnormal levels of these biothiols are often associated with many types of diseases. Therefore, the detection of Cys (or Hcy) is of great importance. In this work, we have synthesized an excellent “OFF-ON” phosphorescent chemodosimeter 1 for sensing Cys and Hcy with high selectivity and naked-eye detection based on an Ir^III complex containing a 2,4-dinitrobenzenesulfonyl (DNBS) group within its ligand. The “OFF-ON” phosphorescent response can be assigned to the electron-transfer process from Ir^III center and C^N ligands to the DNBS group as the strong electron-acceptor, which can quench the phosphorescence of probe 1 completely. The DNBS group can be cleaved by thiols of Cys or Hcy, and both the ³MLCT and ³LC states are responsible for the excited-state properties of the reaction product of probe 1 and Cys (or Hcy). Thus, the phosphorescence is switched on. Based on these results, a general principle for designing “OFF-ON” phosphorescent chemodosimeters based on heavy-metal complexes has been provided. Importantly, utilizing the long emission-lifetime of phosphorescence signal, the time-resolved luminescent assay of 1 in sensing Cys was realized successfully, which can eliminate the interference from the short-lived background fluorescence and improve the signal-to-noise ratio. As far as we know, this is the first report about the time-resolved luminescent detection of biothiols. Finally, probe 1 has been used successfully for bioimaging the changes of Cys/Hcy concentration in living cells.

A new phosphorescent dinuclear cationic iridium(III) complex (Ir1) with a donor–acceptor–π-bridge–acceptor–donor (DAπAD)-conjugated oligomer (L1) as a N^N ligand and a triarylboron compound as a C^N ligand has been synthesized. The photophysical and excited-state properties of Ir1 and L1 were investigated by UV/Vis absorption spectroscopy, photoluminescence spectroscopy, and molecular-orbital calculations, and they were compared with those of the mononuclear iridium(III) complex [Ir(Bpq)₂(bpy)]⁺PF₆⁻ (Ir0). Compared with Ir0, complex Ir1 shows a more-intense optical-absorption capability, especially in the visible-light region. For example, complex Ir1 shows an intense absorption band that is centered at λ=448 nm with a molar extinction coefficient (ε) of about 10⁴, which is rarely observed for iridium(III) complexes. Complex Ir1 displays highly efficient orange–red phosphorescent emission with an emission wavelength of 606 nm and a quantum efficiency of 0.13 at room temperature. We also investigated the two-photon-absorption properties of complexes Ir0, Ir1, and L1. The free ligand (L1) has a relatively small two-photon absorption cross-section (δ_max=195 GM), but, when complexed with iridium(III) to afford dinuclear complex Ir1, it exhibits a higher two-photon-absorption cross-section than ligand L1 in the near-infrared region and an intense two-photon-excited phosphorescent emission. The maximum two-photon-absorption cross-section of Ir1 is 481 GM, which is also significantly larger than that of Ir0. In addition, because the strong BF interaction between the dimesitylboryl groups and F⁻ ions interrupts the extended π-conjugation, complex Ir1 can be used as an excellent one- and two-photon-excited “ON–OFF” phosphorescent probe for F⁻ ions.

A novel conjugated polymer, containing carbazole which acted as an electron-donor moiety, and a Pt(II) complex which acted as an electron-acceptor moiety, was synthesized and characterized. Electrical characterizations for the sandwiched polymer memory device (ITO/polymer/Al) indicate that the polymer possesses electrical bistability and the device exhibits resistive random-access memory. The memory mechanism has been investigated through theoretical calculations and attributed to the formation and dissociation of a charge-transfer state under the applied voltage. The device exhibits excellent memory performances, such as low threshold voltage, high ON/OFF current ratio, and good stability.

Terahertz time-domain spectroscopy (THz-TDS) technique allows us to analyze plastic additives. A series of hindered amine light stabilizers (HALSs), including TMP, PMP, BB-PMP, Chimassorb 944 and 119, and a nitroxide free radical of 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy (HTEMPO) in the matrix of high-density polyethylene are characterized in the range of 0.2–2.6 THz. TMP, PMP, and BB-PMP exhibit individual well-resolved terahertz (THz) absorption spectra at room temperature. Furthermore, a linear relationship of the content of TMP versus the intensity of it first THz absorption peak are demonstrated with the detection limit of about 1.6% (w/w). In addition, PMP exhibit water-dependent characteristic THz absorption spectra. THz-TDS will afford a potential tool to investigate the stabilizing mechanism of HALS and monitor their evolution.

Two fluorene and triphenyl pyridine-based linear and dendronized copolymers, P1 and P2, were synthesized and fully characterized by ¹H-NMR, ¹³C-NMR, and matrix assistant laser desorption/ionization time-of-flight mass spectra, respectively. The absorption, photoluminescence (PL) behavior, and energy band gaps of P1 and P2 relative to those of polyfluorene end-capped with benzene (P0) were examined through UV–vis, photoluminescent spectra, and cyclic voltammetry. The UV–vis absorption and PL emission behavior of P0 and P1 were hardly affected by molecular architecture, while those of P2 were strongly correlated with the dendronized molecular frameworks. Cyclic voltammetry studies indicated the lower highest occupied molecular orbital energy level and wider band gap of P2 thin solid film relative to those of P0 and P1. The new polymers were thermally stable up to 410°C. The better luminance and external quantum efficiencies of P1 relative to those of P0 in polymer light-emitting diode (PLED) applications are due to improved electron injection, charge trapping and recombination at the pyridine sites. Through the experiments, it is found that the triphenyl pyridyl segments and excimers-formation make pronounced contribution to long wavelength emission in P1-based blue light-emitting materials, and the analogous materials containing 2,4,6-triphenyl pyridyl unit of P1 constitute highly attractive materials for white PLED applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

A novel conjugated asymmetric donor–acceptor (CADA) strategy for preventing the redshift in photoluminescence, as well as preserving the merits of donor–acceptor architectures, was proposed and demonstrated for two triazine derivatives, which showed highly efficient, narrow, and blueshifted ultraviolet light emission in solid films along with special aggregation-induced emission behavior. A mechanism of aggregation-induced locally excited-state emission by suppressing the twisted intramolecular charge-transfer emission for the spectacular optoelectronic phenomena of these CADA molecules was suggested on the basis of both experimental measurements and theoretical calculations. By taking advantage of this special CADA architecture, fluorescent probes based on aggregates of conjugated asymmetric triazines in THF/water for the detection of explosives show superamplified detection of picric acid with high quenching constants (>1.0×10⁷ M⁻¹) and a low detection limit of 15 ppb.

This work describes a new one-step large-scale electrochemical synthesis of graphene/polyaniline (PANI) composite films using graphite oxide (GO) and aniline as the starting materials. The size of the film could be controlled by the area of indium tin oxide (ITO). Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and ultraviolet–visible absorption spectrum (UV–vis) results demonstrated that the graphene/PANI composite film was successfully synthesized. The obtained graphene/PANI composite film showed large specific area, high conductivity, good biocompatibility, and fast redox properties and had perfect layered and encapsulated structures. Electrochemical experiments indicated that the composite film had high performances and could be widely used in applied electrochemical fields. As a model, horseradish peroxidase (HRP) was entrapped onto the film-modified glassy carbon electrode (GCE) and used to construct a biosensor. The immobilized HRP showed a pair of well-defined redox peaks and high catalytic activity for the reduction of H₂O₂. Furthermore, the graphene/PANI composite film could be directly used as the supercapacitor electrode. The supercapacitor showed a high specific capacitance of 640 F g⁻¹ with a retention life of 90% after 1000 charge/discharge cycles.

Polyfluorenes containing Ir(III) complexes in the main chain are demonstrated to have promising application in a polymer memory device. A flash-memory device is shown whereby a polymer solution is spin-coated as the active layer and is sandwiched between an aluminum electrode and an indium tin oxide electrode. This device exhibits very good memory performance, such as low reading, writing, and erasing voltages and a high ON/OFF current ratio of more than 10⁵. Both ON and OFF states are stable under a constant voltage stress of −1.0 V and survive up to 10⁸ read cycles at a read voltage of −1.0 V. Charge transfer and traps in polymers are probably responsible for the conductance-switching behavior and the memory effect. The fluorene moieties act as an electron donor and Ir(III) complex units as the electron acceptor. Furthermore, through the modification of ligand structures of Ir(III) complex units, the resulting polymers also exhibit excellent memory behavior. Alteration of ligands can change the threshold voltage of the device. Hence, conjugated polymers containing Ir(III) complexes, which have been successfully applied in light-emitting devices, show very promising application in polymer memory devices.

The diarylethene derivative 1,2-bis-(5′-dimesitylboryl-2′-methylthieny-3′-yl)-cyclopentene (1) containing dimesitylboryl groups is an interesting photochromic material. The dimesitylboryl groups can bind to F⁻, which tunes the optical and electronic properties of the diarylethene compound. Hence, the diarylethene derivative 1 containing dimesitylboryl groups is sensitive to both light and F⁻, and its photochromic properties can be tuned by a fluoride ion. Herein, we studied the substituent effect of dimesitylboron groups on the optical properties of both the closed-ring and open-ring isomers of the diarylethene molecule by DFT/TDDFT calculations and found that these methods are reliable for the determination of the lowest singlet excitation energies of diarylethene compounds. The introduction of dimesitylboron groups to the diarylethene compound can elongate its conjugation length and change the excited-state properties from ππ* transition to a charge-transfer state. This explains the modulation of photochromic properties through the introduction of dimesitylboron groups. Furthermore, the photochromic properties can be tuned through the binding of F⁻ to a boron center and the excited state of the diarylethene compound is changed from a charge-transfer state to a ππ* transition. Hence, a subtle control of the photochromic spectroscopic properties was realized. In addition, the changes of electronic characteristics by the isomerization reaction of diarylethene compounds were also investigated with theoretical calculations. For the model compound 2 without dimesitylboryl groups, the closed-ring isomer has better hole- and electron-injection abilities, as well as higher charge-transport rates, than the open-ring isomer. The introduction of dimesitylboron groups to diarylethene can dramatically improve the charge-injection and -transport abilities. The closed isomer of compound 1 (1 C) has the best hole- and electron-injection abilities, whereas the charge-transport rates of the open isomer of compound 1 (1 O) are higher than those of 1 C. Importantly, 1 O is an electron-accepting and -transport material. These results show that the diarylethene compound containing dimesitylboryl groups has promising potential to be applied in optoelectronic devices and thus is worth to be further investigated.

An intensive investigation of structure–property relationships in the aggregation-induced enhanced emission (AIEE) of luminescent compounds is essential for the rational design of highly emissive solid-state materials. In the AIEE-active compounds N,N′-bis[3-hydroxy-4-(2′-benzothiazolyl)phenyl]isophthalamide and N,N′-bis[3-hydroxy-4-(2′-benzothiazolyl)phenyl]-5-tert-butylisophthalamide, fast photoinduced twisted intramolecular charge transfer (TICT) of the enol excited state is found to be mainly responsible for the weak emission of their dilute solutions. The photoinduced TICT enol excited state is formed with a greatly distorted configuration, due to the large rotation about the CN single bond. This facilitates nonradiative TICT decay from the normal enol excited state to the highly twisted enol excited state, rather than proton-transfer decay to the keto excited state. In aggregates, photoinduced nonradiative deactivation of TICT is strongly prohibited, so that excited-state intramolecular proton transfer (ESIPT) becomes the dominant decay, and hence contributes greatly to the subsequent emission enhancement of the keto form. Molecular design and investigation of analogous single-armed compounds further verifies this kind of AIEE mechanism.

Conjugated asymmetric donor-substituted 1,3,5-triazines (ADTs) have been synthesized by nucleophilic substitution of organolithium catalyzed by [Pd(PPh₃)₄]. Theoretical and experimental investigations show that ADTs possess high solubility and thermostability, high fluorescent quantum yield (35 %), low HOMO (−6.0 eV) and LUMO (−2.8 eV), and high triplet energy (E_T, 3.0 eV) according to the different substitution pattern of triazine. The application as host materials for blue PHOLEDs yielded a maximum current efficiency of 20.9 cd A⁻¹, a maximum external quantum efficiency of 9.8 %, and a brightness of 9671 cd m⁻² at 5.4 V, making ADTs good candidates for optoelectronic devices.

Organic light-emitting diodes (OLEDs) have rapidly progressed in recent years due to their unique characteristics and potential applications in flat panel displays. Significant advancements in top-emitting OLEDs have driven the development of large-size screens and microdisplays with high resolution and large aperture ratio. After a brief introduction to the architecture and types of top-emitting OLEDs, the microcavity theory typically used in top-emitting OLEDs is described in detail here. Then, methods for producing and understanding monochromatic (red, green, and blue) and white top-emitting OLEDs are summarized and discussed. Finally, the status of display development based on top-emitting OLEDs is briefly addressed.

The molecular packing structure in the self-assembled p-n and n-p-n heterostructure oligomers (OT₂O and T₂O₂) was investigated. The macroscopic properties of the two oligomers were systemically investigated by differential scanning calorimetry (DSC), polarized optical microscopy (POM) and X-ray diffraction (XRD), which revealed that the 3D (three-dimensional) assemblies of the two oligomers exhibited obvious differences. The two-dimensional assemblies (2D) of them were identified by scanning tunneling microscopy (STM) on a highly oriented poyrolytic graphite (HOPG) surface. Well-ordered monolayer assembly structures were fabricated by symmetric molecules (OT₂Os), while the ordered dormain of asymmetric molecule (T₂O₂s) could not be clearly resolved. This system, as an excellent example, may provide guidance for the design of the novel p-n heterostructure oligomer and polymer.

Carbazole end-capped starburst molecule based on pyrene core “4CzFP” was synthesized and characterized. The starburst material shows good film-forming ability and bright blue fluorescence. In cyclic voltammetry test, 4CzFP shows a high highest occupied molecular orbital energy level of −5.26 eV, indicating it has good hole-injection ability. The material is quite stable under series of cyclic voltammetry scans, implying its good electrochemical stability. Single-layered electroluminescent device takes on stable blue emission with a peak current efficiency of 0.84 cd/A. Double-layered device by adding Poly(N-vinylcarbazole) (PVK) as a hole-injection layer does not show any improvement, indicating that 4CzFP could be efficiently used as the hole-injection/light-emitting layer. The device performance is largely improved by adding a thin TPBI electron-injection/transporting layer. The peak efficiency reaches 3.28 cd/A and the maximum brightness is over 2200 cd/m². © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010

For the development of excellent optical probes for mercury(II), a series of simple conjugated polymers that contain phosphorescent iridium(III) complexes as receptors for mercury(II) were designed and synthesized. These conjugated polymers showed energy transfer from the polymer host to iridium(III) complex guest in both solution and the solid state. Unexpectedly, they can work as excellent polymer chemodosimeters for mercury(II) by utilizing the mercury(II)-induced decomposition of iridium(III) complex. They exhibit a pronounced optical signal change with switchable phosphorescence and fluorescence, even when the concentration of a solution of mercury(II) in THF was as low as 0.5 ppb. With the addition of mercury(II), the phosphorescent emission intensity of iridium(III) complexes was quenched completely. As the emission from polymer backbones increased, the emission wavelength was redshifted simultaneously, thereby realizing ratiometric detection. Excellent selectivity toward mercury(II) over other potentially interfering cations was also realized. In addition, an obvious emission color change of polymer solution from red to yellow-green was observed, thus realizing a “naked-eye” detection of mercury(II). More importantly, the solid films of these polymer chemodosimeters also exhibited high sensitivity and rapid response to mercury(II), thereby demonstrating the possibility of the fabrication of sensing devices with fast and convenient detection of mercury(II). The sensing mechanism was also investigated in detail. This is the first report on chemodosimeters based on conjugated polymers with phosphorescent iridium(III) complexes.

A novel cationic Ir^III complex [Ir(Bpq)₂(CzbpyCz)]PF₆ (Bpq=2-[4-(dimesitylboryl)phenyl]quinoline, CzbpyCz = 5,5′-bis(9-hexyl-9H-carbazol-3-yl)-2,2′-bipyridine) containing both triarylboron and carbazole moieties was synthesized. The excited-state properties of [Ir(Bpq)₂(CzbpyCz)]PF₆ were investigated through UV/Vis absorption and photoluminescence spectroscopy and molecular-orbital calculations. This complex displayed highly efficient orange-red phosphorescent emission with an emission peak of 583 nm and quantum efficiency of Φ=0.30 in dichloromethane at room temperature. The binding of fluoride ions to [Ir(Bpq)₂(CzbpyCz)]PF₆ can quench the phosphorescent emission from the Ir^III complex and enhance the fluorescent emission from the N^N ligand, which corresponds to a visual change in the emission from orange-red to blue. Thus, both colorimetric and ratiometric fluoride sensing can be realized. Interestingly, an unusual intense absorption band in the visible region was observed. And the detection of F⁻ ions can also be carried out with visible light as the excitation wavelength. More importantly, the linear response of the probe absorbance change at λ=351 nm versus the concentration of F⁻ ions allows efficient and accurate quantification of F⁻ ions in the range 0–50 μM.

The combination of π-stacked with π-conjugated building blocks offers an essential strategy to construct multifunctional organic semiconductors (MOSs) with the unique optoelectrical properties. Covalent hybrids can efficiently avoid the intrinsic phase-separation defects in corresponding blend system. In this contribution, poly(vinylcarbazole) tethered with terfluorene, PVK-TF, as a double-channeled π-stacked and π-conjugated hybrid (SCH), has been constructed via Friedal-Crafts click postmodification (FCCP). The chemical structure and optoelectrical property were determined by GPC, UV–vis, PL, TGA, DSC, and CV. Its PL spectra in the annealing thin film at N₂ atmosphere without low-energy emission bands centered at the 530 nm indicates that no π-stacks between carbazole and TF or among TFs dominate the whole condensed phase, which is in agreement with the intrachain T-shaped π-pitched motifs in molecular modeling simulation due to steric hindrance effect in complicated diarylfluorenes (CDAFs). A supporting prototype stable deep-blue PLED was successfully obtained with an Internationale de l'Eclairage (CIE) coordinates of (0.20, 0.10) and a width at half maximum (FWHM) of about 60 nm at high current density of 100 mA/cm² (35 V). Deep-blue PVK-TF is a promising MOS for hole-transporting and host materials. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5221–5229, 2009

A novel series of kinked star-shaped oligofluorene/triazatruxene hybrids are conveniently prepared via a powerful microwave-enhanced multiple coupling methodology. Constructing kinked star-shaped architectures can effectively suppress crystallization and aggregation. The resulting materials are highly amorphous, showing stable amorphous morphology against crystallization. A triazatruxene core endows the materials with elevated highest occupied molecular orbital (HOMO) levels that are well matched to the anode work function, leading to a significantly improved hole-injection property. They hybrids are highly luminescent in both solution (quantum yield is 0.52–0.80) and the solid-state (quantum yield is 0.45–0.76) with bright blue emission. Remarkably, solution-processed devices displaying single-layer electroluminescence (EL) based on these oligomers exhibit efficient blue EL and demonstrate striking color stability, almost unchanged with increasing driving voltage. The best device performance has a rather low turn-on voltage (3.3 V) and a high device efficiency (2.16 % @ 2382 cd m^–2) as well as a high brightness (7714 cd m^–2 @ 10 V) with CIE coordinates of (0.16, 0.15); it shows remarkably better EL performance than devices based on linear oligofluorene or polyfluorene counterparts. The results prove that an oligomer with kinked star-shaped architecture is extremely promising for efficient and stable blue EL. The reasons for the enhanced functional properties and the improved color stability are discussed in relation to the chemical structures and components.

A series of ionic diiminoiridium complexes [Ir(piq-C∧N)₂(L-N∧N)](PF₆) were prepared, where piq-C∧N is 1-phenylisoquinolinato and L-N∧N are bidentate N-coordinating ligands: 2,2′-bipyridine (bpy), 4,4′-dimethyl-2,2′-bipyridine (mbpym), 5,5′-bis(thiopen-2-yl)-2,2′-bipyridine (tbpyt), and 5,5′-bis(9,9-dioctylfluoren-2-yl)-2,2′-bipyridine (FbpyF). X-ray diffraction studies of [Ir(piq)₂(mbpym)](PF₆) revealed that the iridium center adopts a distorted octahedral geometry. All complexes exhibited intense and long-lived emission at room temperature. The substituents on the 2,2′-bipyridine moieties influence the photophysical and electrochemical properties. The excited states were investigated through theoretical calculations together with photophysical and electrochemical properties. It was found that the excited state of the [Ir(piq)₂(FbpyF)](PF₆) complex can be assigned to a mixed character of ³LC (π_N∧Nπ*_N∧N), ³MLCT, ³LLCT (π_C∧Nπ*_N∧N), and ³LC (π_C∧Nπ*_C∧N). In addition, the alkylfluorene-substituted complex, [Ir(piq)₂(FbpyF)](PF₆), hadrelatively high quantum efficiency and good film-forming ability, and it was expected to be a good candidate for lighting and display applications. A nondoped, single-layer device that incorporates this complex as a light-emitting layer was fabricated and red phosphorescence was obtained.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

The photoluminescence (PL), electrochemical, and electroluminescence (EL) properties of Eu^III complexes, [Eu(cppo)₂(tta)₃] (1) and [Eu(cpo)₂(tta)₃] (2; TTA=2-thenoyltrifluoroacetonate) with two carbazole-based phosphine oxide ligands, 9-[4-(diphenylphosphinoyl)phenyl]-9H-carbazole (CPPO) and 9-(diphenylphosphoryl)-9H-carbazole (CPO), which have different bipolar structures, donor–π-spacer–acceptor (D–π–A) or donor–acceptor (D–A) systems respectively, are investigated. The CPPO with D–π–A architecture has improved PL properties, such as higher PL efficiency and more efficient intramolecular energy transfer, than CPO with the D–A architecture. Gaussian simulation proved the bipolar structures and the double-carrier injection ability of the ligands. The carrier injection abilities of triphenylphosphine oxide, CPO, and CPPO are gradually improved. Notably, the Gaussian and electrochemical investigations indicate that before and after coordination, the carrier injection ability of the ligands show remarkable changes because of the particularity of the D-π–A and D–A systems. The electrochemical studies demonstrate that coordination induces the electron cloud to migrate from electron-rich carbazole to electron-poor diphenylphosphine oxide, and consequently increases the electron-cloud density on diphenylphosphine oxide, which weakens its ability for electron affinity and induces the elevation of LUMO energy levels of the complexes. Significantly, the π-spacer in the D–π–A system exhibits a distinct buffer effect on the variation of the electron-cloud density distribution of the ligand, which is absent in the D–A system. It is demonstrated that the adaptability of the D–π–A systems, especially for coordination, is stronger than that of D–A systems, which facilitates the modification of the complexes by designing multifunctional ligands purposefully. 1 seems favorable as the most efficient electroluminescent Eu^III complex with greater brightness, higher efficiencies, and more stable EL spectra than 2. These investigations demonstrate that the phosphine oxide ligands with D–π–A architecture are more appropriate than those with D–A architecture to achieve multifunctional electroluminescent Eu^III complexes.

To investigate the fine optoelectronic difference of the target oligomers with or without peripheral fluorene moieties, two dumbbell-shaped oligomers (F0 and F1) were designed and convergently prepared via Suzuki coupling reaction. The molecular structures of the oligomers were fully characterized by ¹H NMR, ¹³C NMR, and MALDI-TOF mass spectra, respectively. The absorption, photoluminescent behavior, and energy band gaps of the oligomers were examined through UV–vis, photoluminescent spectra and cyclic voltammetry. The experimental results demonstrate that the absorption and photoluminescent properties are little affected by molecular architecture, while the absolute photoluminescence quantum efficiency of films and energy band gaps derived from cyclic voltammetry in solution are strongly correlated with the molecular frameworks. The observed energy band gaps of oligomers are further validated by the different molecular orbital contours of the HOMO energy levels from theoretical calculations. Preliminary electroluminescent investigations for F1 have also been conducted and discussed. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1548–1558, 2008