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For drop-on-demand (DOD) inkjet printing, stable and single ink droplet formation without satellite dots is the key to improve the print quality. The formation of stable and single droplet is influenced by filament break up and the polymer chain’s coil–stretch transition behavior. In this paper, the droplet formation behaviors of polyfluorene (PFO) ink at various driving voltages (V), polymer chain’s coil–stretch transition mechanism and its effects on single ink droplet formation are investigated. It indicates that when 58 63 V, Wi > 0.5, the PFO molecular chain is stretched because of the high hydrodynamic forces, resulting unwanted satellite droplets. When 55

Analysis of stability and degradation of inverted organic solar cells (iOSCs) formed by the blend PTB7-Th:PC70BM, with different stacks of electron transport layers (ETLs) PFN, PFN/LiF, LiF/PFN, LiF and without one are manufactured under N2 environment. The degradation study of the iOSCs is done following ISOS-D1 protocols under air environment, up to 7110 h. Performance parameter obtained from J-V curves such as open circuit voltage (Voc), short circuit current density (Jsc), fill factor (FF) and power conversion efficiency (PCE) are analyzed for each group of iOSCs with the above mentioned different stacks of ETLs and compared between of them. The cell manufactured with the stack PFN/LiF shows the highest stability over time and its TS80 is reached to 201 h. Cells with the stack LiF/PFN and PFN show their TS80 to 153 h and 144 h, respectively. The S-shape is presented on all J-V curves under study and are modeled using an equivalent circuit of three-diodes, in order to understand the physical mechanism related to it.

In the tetrabutyl titanate solution via a sol-gel method, the nano-TiO2@polyfluorene composite particles were successfully prepared from the polyfluorene particles which were obtained by grinding fluorene with FeCl3 through the solid-state oxidative coupling reaction. The morphology and optical properties of the composite particles were characterized by scanning electronmicroscope, high resolution transmission electron microscopy, X-ray photo electron spectrometer, X-ray diffractometer, UV–visible diffuse reflectance spectroscopy, photoluminescence spectra and so on. The composite particles presented excellent photocatalytic activity on the degradation of triphenylmethane dyes, such as malachite green and rhodamine B under sunlight or under visible light. The photocatalytic reusability was investigated up to six successive cycles and the composite particles still retained their high activity of photodegradation ratio for malachite green. The mechanism of photocatalysis has been were discussed. The high surface area and effective photoinduced electrons and holes of TiO2@polyfluorene led to the enhanced photocatalytic activity. Consequently, the nano-TiO2@polyfluorene composite particles can be employed as an efficient photocatalyst to treat the organic pollutants.

The use of conjugated polymer blends is an option to improve technological devices. The present work used a nitrile rubber (NBR) blend as a matrix and a conjugated polymer derived from polythiophene and/or polyfluorene. These materials were prepared and exposed to UV light (365 nm) for different periods. The blends were characterized by luminescent properties (absorption and emission) and submitted to infrared spectroscopy and thermogravimetric analysis before and after exposure to the light. The results showed a good rubber protection for up to 7 h of exposure, before degradation of the conjugated polymer. Afterwards, a new band was observed in the UV–vis absorption, and the infrared spectra showFied the formation of alcohols and/or peroxides. The thermogravimetric analysis of the three copolymers did not present significant changes compared to the beginning of the degradation and the shape of the curves. Therefore, we concluded that the NBR matrix was efficient in protecting the conjugated polymer for up to 7 h of exposure to light.

An effective synthetic route for preparation of oligo(fluorene-co- dibenzothiophene-S,S-dioxide)s (trimer SOF2, pentamer SOF4, heptamer SOF6 and nonamer SOF8) based on meta- or para-linked dibenzothiophene-S,S-dioxide (SO) unit as the core was developed by convergence method, for which the intermediates unilateral boric acid esters were prepared by one-step palladium-catalysed Suzuki cross-coupling reaction. The resulting oligomers exhibited excellent thermal stability with thermal decomposition temperature exceeding 415 °C, and high photoluminescent quantum yield in the solid state (52–81%). The UV–vis absorption and photoluminescence emission maxima of the oligomers exhibited gradual bathochromic shifts from the trimer to the nonamer, approaching those of the previously reported polymer PFSO10 containing 10 mmol% of the SO unit in the polyfluorene backbone, demonstrating the similar photophysical properties of the nonamer SOF8 and polymer PFSO10. The highest occupied molecular orbital energy level gradually decreased and the lowest unoccupied molecular orbital energy level steadily increased from the trimer SOF2 to the nonamer SOF8. The obtained oligomers displayed pure blue-light emission with the maximal emission peaked at about 440 nm and superior EL spectral stability compared with PFSO10 upon varying the current density from 100 mA cm−2 to 500 mA cm−2, in addition to more balanced hole and electron fluxes. With the device configuration of ITO/PEDOT:PSS/oligomer/CsF/Al, a maximum luminous efficiency of 2.75 cd A−1 with Commission Internationale de l’Eclairage (CIE) coordinates of (0.16, 0.15) was obtained for the device based on 37SOF8. The efficiency increased by 88% compared with the device based on 37PFSO10 (1.46 cd A−1). A similar enhancement in efficiency was also achieved for the device based on 28SOF8. These results indicate that the obtained oligomers are very promising candidates for structurally well-defined blue-light- emitting materials with high efficiency and reproducibility.

Herein, we have developed an efficient approach for folate receptor (FR) over expressed cancer cell targeting and imaging through non-covalent conjugation between folic acid (FA) and a polyfluorene based amphiphilic, fluorescent polymer nanoprobes (CPF) by fluorescence “turn off” mechanism. The pH dependent supramolecular complexation/decomplexation tendency of CPF nanoprobes with FA provides the effective reversible fluorescence “turn off/turn on” of CPF fluorescence. The complete pH dependent complexation/decomplexation phenomena is characterized by photophysical and morphological characterization. The FESEM image study reveals the alteration of nanosphere structure of CPF to interconnected network after complexation with FA at pH 9 and consequently restoration of nanosphere morphology by decomplexation at pH 2. Again, the CPF nanoprobes exhibit 91% fluorescence quenching even in physiological pH 7.4 to reveal that the nanoprobes can be a suitable candidate for FA targeted turn-off fluorescent nanoprobes for FA pre-treated FR-positive cancer cells in vivo study. The fluorescence of CPF nanoprobes is significantly quenched in FA pre-treated FR-positive B16F10 cancer cell whereas it remains unchanged in FR-non overexpressed normal human corneal cell (HCE cells) even after FA pre-treatment. Furthermore, the present study can provide a dissimilar protocol to use a “turn off” fluorescent nanoprobe for FR-positive cancer cell imaging using free FA and fluorescent polymer nanoparticle rather than the conventional direct FA-fluorescent conjugated polymer complex.

Polyfluorene-based conjugated polyelectrolytes as efficient cathode buffer layers have powerfully improved the device performance of polymer solar cells, but the p-type nature of backbones make them work efficiently only in very thin film (2∼5 nm). In this work, three new polyfluorene-based conjugated polyelectrolytes with self-doping effect, namely poly[(9,9-bis(6′-N,N,N-trimethylammoniumbromide)hexyl)fluorene-alt-(5,6-difluoro-4,7-di(thiophen-2-yl)benzo[c] [1,2,5]thiadiazole)] (PFTBT-NBr), poly[(9,9-bis(6′-N,N,N-trimethylammoniumbromide)hexyl)fluorene-alt-2,5-bis(2-octyldodecyl)-3,6-bis(thiophen-2-yl)-pyrrolo [3,4-c]pyrrole-1,4-dione (PFTDPP-NBr) and poly[(9,9-bis(6′-N,N,N-trimethylammoniumbromide)hexyl)fluorene-alt-N,N′-bis(2-decyltetradecyl)-1,7-bis(thien-2-yl)-perylene-3,4:9,10-tetracarboxylic-diimide (PFTPDI-NBr) are designed and synthesized as buffer layer for PSCs. These conjugated polyelectrolytes have the same polar side chains, but differ in the conjugated backbones which are composed of fluorene alternated with different electron-withdrawing group, benzothiadiazole (BT), diketopyrrolopyrrole (DPP) and perylenediimide (PDI) respectively. The n-type polarity of the conjugated backbones is found to be substantially strengthened by varying the electron affinity and conjugated planarity of these backbones. As a result, employing these conjugated polyelectrolytes as cathode buffer layers for PSCs can effectively boost the device performance. Notably, an excellent thickness tolerance (∼30 nm) of polyfluorene-based polyelectrolytes, especially for PFTPDI-NBr, is achieved in the PSCs, originating from the higher electron mobility and conductivity, better interface contact between active layer and electrode, and favorable morphology of active layer.

Three sets of polyfluorenes grafting one/two orange emissive groups on central or terminal fluorene unit have been synthesized successfully through the catalyst-transfer polymerization. The molecular weights linearly increase with increase in the feed ratios of [monomer]/[catalyst] in a certain molecular weight range. The initiators with bis(2,6-diisopropylphenyl)imidazolin-2-ylidene) (IPr) as the ancillary ligand show better catalytic activity, leading to higher molecular weight of up to 126.3 kDa. All polymers in toluene have the similar absorption spectra to polyfluorene homopolymer, while the weak absorption bands of 420–500 nm are observed only in the polymers with low molecular weight. Photoluminescence spectra display a dominant blue emission from the polyfluorene backbone and a weak orange emission (508–661 nm) from the orange group. The clearly enhanced orange emission in the polymers with low molecular weight is mainly ascribed to the intramolecular Forster energy transfer from the polyfluorene segment to the orange group, which is further confirmed by the electroluminescent behavior of the polymers.

It is well known that upon electronic excitation various π-stacked dimers readily exhibit excimer formation, facilitated by a perfect sandwich-like arrangement between the chromophores. However, it is unclear whether such a dimer is also capable of electron transfer upon excitation, if a strong electron-donating group is covalently attached. In this work, we probe the nature of the excited state in a series of cofacially arrayed polyfluorene derivatives with electron-rich aromatic donor attached via a methylene linker. Our studies show that in all cases excimer formation is energetically favorable, and promotion of a charge-transfer state in such systems is possible but requires a free energy for electron transfer far exceeding 1 V. These findings shed light on important design principles for molecular scaffolds capable of stabilizing both excimeric and charge-transfer states upon their excitation.

The application of emissive intermolecular states of non–planar Iridium (III) phosphors in white emitting phosphorescent electroluminescent devices is almost unexplored. Here, I investigate the competing mechanisms of energy transfer and charge trapping as function of temperature in devices whose active layer contains an Ir(III) complex with a rigid cyclometallated ligand structure blended in a polyfluorene host. Keeping a low doping ratio it is possible to boost the formation of the low–energy β phase in the polymer matrix as well as generate the intermolecular emissive state in the Ir compound so as to enable white emission with CIE coordinates (0.32, 0.23) and external quantum efficiency of 2.32 ± 0.11% at 25 mAcm-2 in a single–layer device structure. This device performance is higher than those previously reported for fully solution–processed devices based on intermolecular excited states.

Highly efficient inverted polymer solar cells were demonstrated by incorporating a polyfluorene electrolyte to mitigate the intrinsic external defects of ITO cathode. The interfacial compatibility of solution-processed active layer and the cathode was improved using PFN/PFBT composite interlayer due to the optimized surface morphology and increased interfacial area. The hybrid PFN/PFBT electron transport layer suppressed recombination of the photo-excited carriers at the interface and facilitated subsequent charge transfer into the cathode. The leakage current as well as the series resistance of the device was decreased and the device reliability was improved. As a result, the electron collection efficiency from the active layer to the cathode was enhanced and the highest power conversion efficiency of 9.74% was achieved. The incorporated PFBT layer aimed to overcome the intrinsic defects of conventional transparent buffer layer based on the transition metal oxides, which make it spendable to fabricate the commercially viable photovoltaic devices.

A novel conjugated polyfluorene derivative (PCFSe) was successfully synthesized, with benzo[c][1,2,5]selenadiazole in polyfluorene backbone and N-alkylcarbazole in the side chain. PCFSe shows an orange-red fluorescence emission at 570 nm with a high glass transition temperature and excellent thermal stability. In the fluorescence titration experiments, PCFSe as fluorescent sensor exhibits varying degrees of fluorescence quenching towards different nitroaromatics, in which picric acid (PA) detection has the highest sensitive response with the Stern-Volmer quenching constant KSV value of 1.2 × 104 M−1 and the calculated detection limit of 0.27 ppm. Meanwhile, the quenching effect of PA to PCFSe has no significant change even in the presence of other nitroaromatics, indicating a selective PA detection. Furthermore, the paper strips were also fabricated to detect PA, achieving a practical application in fast, easy and on-site detection of nitroaromatic explosives.

Blue light-emitting polymers were synthesized by Suzuki polycondensation via introducing 9,9-dioctylfluorene [2,3-b]benzo [d]thiophene-S,S-dioxide (BTOF) unit into the polyfluorene and polycarbazole backbone, respectively. All the polymers show high fluorescence quantum yield and thermal stability. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of the polymers reduce slightly with increasing the content of BTOF in the polymers. The polymers exhibit stable electroluminescence spectra with the variation of applied current densities up to 300 mA cm−2. The peak luminous efficiencies (LEmax) of 3.7 and 3.1 cd A−1 (corresponding to a maximum external quantum efficiencies (EQEmax) of 3.5 and 2.5%) with the luminances of 10085 and 19662 cd m−2 were obtained at a turn on voltage of 3.0 and 3.2 V, respectively, based on PF-BTOF30 and PCz-BTOF20 with a single-layer configuration of ITO/PEDOT:PSS/polymer/CsF/Al. Compared to the homopolymers PF and PCz, the enhanced device efficiencies about 6–8 times and the improved device lifetime exceeded an order of magnitude of the copolymers implied that introducing BTOF unit into the polymer backbone could be a promising strategy for the development of highly efficient blue light-emitting polymers.

The photo- and electroluminescent properties of a copolymer containing fluorene, terpyridine and complexed sites with trivalent europium ions (LaPPS66Eu) was investigated. The non- complexed backbone (LaPPS66) and an analogous chemical structure of the ligand/Eu3+ site (LaPPS66M) as a model compound were used for comparison and interpretation of the photophysical properties. Experiments were carried out using PVK as a dispersive matrix either in a blend form or in a bilayer configuration. Absorption and emission spectra, time-resolved emission spectra (TRES) and Forster Resonance Energy Transfer efficiency ( ) were used to account for the differences found for the photophysical properties of each configuration.

Unique coplanar β-conformation of polyfluorene, endowed with long effective conjugated length, is promising to form ordered and oriented structures that can result in improved carrier mobility, polarization emission and excellent spectral stability. Herein, a series of polydiarylfluorenes of different side-chains (PHDPF, PODPF or PNDPF) and poly (9-vinylcarbazole) composite nanofibers were prepared via electrospinning approach. It is observed that β-phase can be obtained in PODPF electrospun nanofibers whereas absent in those of PHDPF and PNDPF systems. It can be demonstrated that the optimal chain length for polydiarylfluorenes to β-conformation is an octyl side chain in electrospinning. In contrast with the electrospun nanofibers, there was no β-phase in the corresponding spin-coated film. For the β-phase electrospun nanofibers, the fluorescence quenching sensitivity on 2, 4-dinitrotoluene (DNT) vapor was obviously higher than that of amorphous electrospun nanofibers and spin-coated film, respectively. Synergistic molecular design and electrospun processing may offer a fascinating strategy for the control of polymer conformation to the adjustment of nano and micro optical devices such as organic fluorescence sensors, lasers and light-emitting diodes.

The paper focuses on the preparation of phenothiazine based nanoparticles, both in liquid and solid states, by reprecipitation in water and solvent induced phase separation respectively. Polymethylmethacrylate was used as an inert matrix and polyfluorene as a luminescent matrix. The morphological features of the nanoparticles were investigated by dynamic light scattering, and SEM, AFM and POM microscopy, which revealed their supramolecular ordering as nanocrystals. Their photophysical behaviour was monitored by UV–vis and photoluminescence spectroscopy. The nanocrystals emitted green light, with higher efficiency compared to the bulk crystals, reaching an absolute quantum yield of 35% in water, 45% in polymethylmethacrylate, and 39% in polyfluorene.

A series of novel red-emitting conjugated polymers were synthesized, adopting host-guest technique, with fluorene-carbazole backbone and low bandgap unit, 1,1-dimethyl-3,4-di(triphenylamine)-2,5-dithienyl)silole, as the guest chromophore. Those materials were well characterized by nuclear magnetic resonance, elemental analysis, absorption and fluorescence spectra, and cyclic voltammetry. The HOMO energy levels of these three copolymers locate within the range of −5.40∼−5.33 eV which are greatly elevated compared with that of polyfluorene and match the work funtions of ITO and ITO/PEDOT:PSS (about −4.7 eV and −5.0 eV, respectively) better, indicating smaller hole-injection barrier. Polymeric light-emitting diodes (PLED) with the configuration of ITO/PEDOT:PSS(40 nm)/PFO-Cz-TPATST(80 nm)/CsF(1.5 nm)/Al(100 nm) and ITO/PEDOT:PSS(40 nm)/PFO-Cz-TPATST(80 nm)/1,3,5-tris(2-N-phenylbenzimidazolyl)benzene (TPBI) (30 nm)/CsF(1.5 nm)/Al(100 nm) were fabricated respectively. Highest luminous efficiency of 1.06 cd A−1 was achieved.

It is well known that hypoxia is a critical parameter with respect to several pathologies, like solid tumors. Hence, it is necessary to realize highly sensitive and selective monitoring of oxygen levels in biological systems. Phosphorescent iridium(III) complexes are an excellent class of oxygen probe through the energy transfer from triplet excitons to oxygen molecules. Current research mainly focuses on the neutral and cationic complexes, while the anionic ones received few attentions. Herein, we designed a series of anionic iridium(III) complexes with different C^N ligands and investigated their oxygen-sensing capability in solution and living cells. Importantly, based on the metathesis reactions of the anionic iridium(III) complexes with oxygen-insensitive cationic polyfluorene, water-soluble polymer soft salt P1 was synthesized successfully. Thus, ratiometric luminescent and reversible polymer hypoxia probe can be obtained because P1 can give dual emission with oxygen-sensitive phosphorescence from the iridium(III) complexes and reference fluorescence from polyfluorene, respectively. Furthermore, the photoluminescence lifetime imaging at different oxygen levels exhibited that P1 is an excellent oxygen probe utilizing the sensitive phosphorescent lifetime to oxygen level. To our knowledge, this is the first report about the application of anionic iridium(III) complexes and their conjugated polymer soft salts in biosensing and bioimaging fields.

Stable and single droplet generation is essential in drop-on-demand (DOD) inkjet printing process to deposit homogeneous and flat film. However, polymer's rheological properties and viscoelasticity can influence filament break up and droplet formation, which may lead to the formation of satellite droplets. Controlling the Z constant (related to fluid viscosity, and surface tension) and Weissenberg (Wi) number can suppress the satellite droplets and get stable and single droplet. Here, mixed solvents (chloride benzene (CB) and high viscosity cyclohexylbenzene (ChB)), different molecular weight and concentration were employed to tune the polyfluorene (PFO) viscosity, surface tension and viscoelasticity. According to the droplet ink-jetting behavior of different CB/ChB ratio, PFO molecular weight and concentration, it's found that only when the speed of the secondary droplet is faster than that of the primary droplet, a single droplet could be formed. At last, we concluded that for PFO inks 9 ≤ Z ≤ 55, Re ≥ 3 and Wi = 0.5 were adequate judgement for a stable and single droplet formation and the two factors should be controlled simultaneously to ensure a stable and single droplet.

Design of supramolecular organization to produce large optical activity involves multiple factors either internal as external. In this paper, we report on the synthesis, systematic study and theoretical modeling of a series of chiral polyfluorene derivatives, whereby we identify the main parameters controlling the chiroptical activity of polymer films. For each polymer, five empirical/theoretical properties were chosen, due to their effect on the chirality parameter: glass transition temperature, dissymmetry factor, molar mass, helix tightness and the inverse of interconversion energy. We introduce a radar graph exhibiting the influence of chirality metric on these five parameters and their interplay. The polygonal area in the radar graph and the chirality parameter presented a direct relationship. Such graph can provide pre-screening of polymer properties, based on both experimental measurements and theoretical considerations and help choosing the right combination of parameters, leading to a material with the best properties.

Different weight composition of polyfluorene (PFO) ((0.625 mg, 1.250 mg, and 2.500 mg) have been prepared and dissolved in toluene before spin coating on indium tin oxide (ITO) glass substrates. Post-deposition annealing was carried out to transform the wet film to solid film. High resolution X-ray diffraction analysis has detected the presence of broad diffraction peaks belonged to β-phase of PFO in all of the investigated samples. An onset of crystallization for the β-phase happened in the 2.500 mg PFO coated sample. Photoluminescence emission spectra of the β-phase was increased in intensity. Besides, a red shift happened due to an increase in energy transfer from glassy to β-phase, following an increase in conjugation length in the PFO backbone. The formation of crystalline β-phase and increased conjugation in the 2.500 mg PFO coated sample. Hence, the corresponding current-voltage characteristic showed that the highest current conduction has been perceived by the sample. A schematic diagram showing energy band diagram of the Al/PFO/ITO structure was presented and discussed in association with structural, morphological, and optical characteristics of the PFO films.

Conjugated polyelectrolytes (CPEs) have achieved vast success in organic electronics due to their appealing opt-electrical properties and convenient solution-processability. However, most of the existing n-type CPEs commonly exhibit distinct light capture in visible region. The attainment of novel n-type CPEs possessing both high electron conductivity and high visible light transparency is significant while still challenging. Herein, optimized amount of organic diradicals achieved by benzobisthiadiazo (BBT) unit are intentionally introduced into the backbone of the representative wide-band-gap polyfluorene-based conjugated polyelectrolyte via ternary copolymerization. The incorporation of diradical canonical structure could promote the quinoid resonance of conjugated skeleton, leading to increased self-doping effect. Consequently, the copolymerized CPE exhibits high visible light transmittance (AVT over 85%) and enhanced electron conductivity compared to the referenced CPE. The fabricated organic solar cell devices with the new-designed polyelectrolyte as the cathode interface layer can achieve high power conversion efficiencies of more than 16%, which is not susceptible to the thickness up to 50 nm. This work provides a feasible molecular modification strategy via organic diradicals regulation to obtain high performance n-type self-doped conjugated polyelectrolytes.

In this work, a series of hyperbranched white-emitting conjugated polymers were synthesized with polyfluorene (PF) as the branches and three-dimensional-structured spiro[3.3]heptane-2,6-dispirofluorene (SDF) as the conjugated branching point by one-pot Suzuki polycondensation, where 4,7-dithienyl-2,1,3-benzothiadiazole (DBT) as orange-light emitting unit and fluorene-containing polyhedral oligomericsilsesquioxanes (POSSs) as conjugated linking monomer were introduced into the backbones to obtain white-light emission. The influence mechanism of POSSs for hyperbranched white-emitting polymers was explored by adjusting the feeding ratios of fluorene-containing POSSs (from 1 to 20 ​mol%). The results indicated that the synthesized polymers still maintained the high thermal stabilities, and exhibited the improved amorphous film morphology and hydrophobicity, which were beneficial for obtaining optimized interface between the aqueous hole transport layer Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT: PSS) layer and polymer light-emitting layer in device fabrication. As a consequence, all of the fabricated devices with the hyperbranched polymers as light-emitting layers realized white light-emission, and the optimized device exhibite good electroluminescent (EL) performance with Commission Internationale de l’Eclairage (CIE) coordinates at (0.32, 0.33) and maximum color rendering index (CRI) of 96. The fluorene-containing POSSs modified hyperbranched copolymers with broad full width at half maximum (>284 ​nm) are attractive candidates for sunlight-style white polymer light-emitting diodes.

We presented comprehensive photoluminescence (PL) and electroluminescence (EL) studies of polyfluorene based electroactive polymer (SF4) containing double bond side chain to investigate its characteristics as a function of temperature. Annealing treatment was conducted for thin films on glass substrates and also for the organic light emitting diodes (OLEDs) at different temperatures. While polymer thin film coated on to glass substrate annealed at 150 °C shifted white color emission. It was implying that the emission was taking place interchain interaction. Phase modulation at higher annealing temperatures was occurred on the thin film as shown AFM images. Further, annealed polymer film with 120 °C exhibited the best performance in OLED device with luminance 5241 cd m −2 , a maximum efficiency 1.54 cd A −1 and external quantum efficiency 0.54% compared to other polymer films annealed with different temperatures.

Polyfluorene (PF) and oligofluorene (OF) with N1-hexylcytosine side chains were synthesized by Pd-complex-catalyzed condensation reactions starting from a newly synthesized monomer. The UV–vis spectra of the PF exhibit the absorption maximum at a longer wavelength than that of the OF, thus revealing that a π-conjugation system extends along the polymer chain. The PF and OF are photoluminescent in solution, and their photoluminescence (PL) intensities are gradually decreased by the addition of nucleosides such as adenosine, cytidine, and guanosine to the solution. The decrease in PL intensity is likely caused by photoinduced charge transfer (PCT) from the PF's and OF's backbones to the nucleosides, within the complexes generated by hydrogen bonding between the PF and OF cytosine group at their side chains and the nucleosides. Among the nucleosides, guanosine acted as the most effective PL quenching agent. Cyclic voltammetry (CV) analysis of the OF showed that it is electrochemically active.

The electroluminescent (EL) properties of two polyfluorene-based (poly(9,9-di-n-octylfluorenyl-2,7-diyl) (PFO) and poly[(9,9-di-n-octylfluorenyl-2,7-diyl)-alt-(benzo[2,1,3]thiadiazol-4,8-diyl)] (F8BT)) organic light-emitting diodes (OLEDs) were investigated. Two diode configurations were tested: blends with emissive layers of PFO (higher weight percentage, from 98 to 99.8 wt.%) and F8BT (lower weight percentage, from 0.2 to 2 wt.%) and bilayers of PFO/F8BT. To understand the diode performances, we compared the photoluminescence (PL) and the EL emissions of both configurations. PL emission decays showed that the fluorescence resonant energy transfer (FRET) efficiency is higher for blends that have less of the F8BT component than in bilayers. For the bilayer systems, however, the FRET efficiency is approximately 50%, confirming the significant inter-penetration of these two polymers. Upon decreasing the F8BT concentration in the blend or the F8BT film thickness in the bilayer, the EL emission shifted toward the blue color due to a more significant contribution from the PFO emission. The EL color can be tuned between green (from the F8BT) and blue (from the PFO) shades by adjusting the polymer composition. The differences between the PL and EL band profiles were discussed.

Inverted polymer light-emitting diodes (IPLED) were fabricated by using polyfluorene (PF-FSO10) as the emissive layer, polyethyleneimine ethoxylate (PEIE) as the interlayer, and 1,3,5-tris(N-phenylbenzimidazol-2-yl)benzene (TPBI) as the electron-transport layer with the configuration of ITO/ZnO/PEIE/TPBI/PF-FSO10/MoO 3 /Al. Thermal annealing PF-FSO10 made the hole transporting ability decreased, the electron transporting ability enhanced, and thus, jointly promoted the carrier balances in the emissive layer. Inserting a TPBI layer between the PEIE and PF-FSO10 much enhanced the electron transportation and reduced the exciton quench on the ZnO interface. Therefore, the inverted blue light-emitting diode was obtained with a luminous efficiency of 6.8 cd A −1 (an external quantum efficiency of 7.1%), and the CIE color coordinates of (0.15, 0.15), which was among the highest efficiency values in solution-processed inverted blue fluorescent light-emitting diodes.

Two kinds of novel single white polymers, lateral-chain type and star-like type, were designed and synthesized by introducing di( p -methoxyphenyl)maleimide (λ em = 540 nm) or dithienylmaleimide (λ em = 558 nm) guest into the side chain of linear polyfluorene (LPF-TMs and LPF-PMs), and diphenylmaleimide (λ em = 500 nm) guest into the core of star-like polyfluorene (SPF-PMs). By adjusting the feed ratio of maleimide and fluorene units, the resulting single white polymers exhibited a dual emission including blue emission (ca 430 nm) from polyfluorene host and yellow (ca 536 nm) emission from diarylmaleimide guest. Their electroluminescent properties were investigated in the single-emitting-layer devices fabricated by solution process with the configuration of ITO/PEDOT:PSS/polymer/TPBI/LiF/Al. Compared with main-chain type polymers, LPF-PMs and SPF-PMs displayed better electroluminescent performance with the maximal current efficiency of 8.77 cd/A and 10.30 cd/A, respectively. Due to the balanced blue and yellow emission, LPF-TM03 containing 0.3% guest get the relatively pure white light with CIE coordinates value of (0.31,0.33). The results indicate that diarylmaleimide is a kind of utility guest to construct easily synthesized, structurally diverse and highly efficient white polymers.

A novel polymer is designed to serve as the conductive binder for high-capacity silicon anodes in lithium ion batteries (LIBs), aiming to address fast capacity fade and poor cycle life of silicon anodes caused by large volume change during repeated cycles. Abundant carboxyl groups in the polymer chain can effectively enhance the binding force to Si nanoparticles (NPs) and the n-type polyfluorene backbones of the polymer significantly promote the electronic conductivity under the reducing environment for anodes, dual-features of which can maintain electronic integrity during lithiation/delithiation cycles. Notably, the polymer can react with the polar groups on the surface of Si NPs to form strong chemical bonds, thus truly maintaining the electrode mechanical integrity and good electronic conductivity after repeated charge/discharge process. The as-assembled batteries based on the polymer without any conductive additive exhibit a high reversible capacity (2806 mA h g−1 at 420 mA g−1) and good cycle stability (85.2% retention of the initial capacity) after 100 cycles.

The film quality is the core to produce long-life and efficient organic light emitting devices by ink-jetting printing technology which is deeply related to the ink droplet coalescence process, especially the coalescence bead morphology and thickness. However, the fluid flow from impacted drop to the previously deposited drops (drop to bead flow) usually leads to an asymmetry and heterogeneity of coalescence beads during droplets coalescence process in the substrate. Here we reduce the spreading speed of impacted drops to achieve a symmetric and homogeneous coalescence effect, by controlling the drops to deposit firstly and then coalescence. A uniform linear line morphology with a smooth straight edge and symmetric ends was obtained at drop distance 1.35 ≤ y ≤ 1.60. Via adjusting the chloride benzene (CB)/cyclohexylbenzene (ChB) proportion of ink formula, when the γ/η value decreases to 4.73 m/s, the h1/h2 value is nearly 1.04, homogeneous bead obtained. Uniform and homogeneous bead was formed for 80/20 CB/ChB sample with a 4.73 m/s surface tension/viscosity ratio. The appropriate matching of the relationships of the spreading and coalescence speed of impacted drops plays a critical role for the final bead morphology during the droplet coalescence. The spreading and coalescence speed have a finite matching for the 80/20 CB/ChB sample with a 4.73 γ/η value, forming uniform beads.

The blue light-emitting polymers PF-CzBTOs and PCz-CzBTOs were synthesized by Suzuki polycondensation via introducing ortho -linking N -(2-decyltetradecyl) carbazole bis- [2,3-b,6,7-b]benzo[ d ]thiophene- S,S -dioxide (CzBTO) into the polyfluorene (PF) and polycarbazole (PCz) backbone, respectively. All the resulted copolymers showed high thermal stability with the glass transition temperatures (T g ) of over 130 ° C. The fluorescence quantum yields (Ф PL ) are in the range of 41%–59% and 20%–31% for PF-CzBTOs and PCz-CzBTOs, respectively. The highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy levels of the copolymers are basically unchanged with the increase of CzBTO content in the copolymers. The PL spectra of copolymers showed only a faint broadening with the increase of CzBTO content in the copolymers, and with the increase of the solvent polarities, indicating no remarkable ICT effect in polymers containing ortho -linking CzBTO moiety. The copolymers showed a pure blue emission with a CIE coordinates of (0.15, 0.11) for the PF-CzBTO10, and a CIE coordinates of (0.17, 0.18) for PCz-CzBTO15. The results indicated that the strategy of introducing ortho -linking CzBTO unit into the polyfluorene or polycarbazole backbone can effectively restrain ICT effect and result in the pure blue emission.

Recently, significant efforts have been made to develop highly efficient organic light-emitting diodes (OLEDs) employing reverse intersystem crossing (RISC) owing to its capability of harvesting non-emissive triplet states. Up to date, most of such emitters were small-molecular-weight materials that needed to be doped into a host material. Due to the advantages of ease device fabrication and excellent photoluminescent properties, polymer-based RISC emitters should be developed. In this study, we reported a polyfluorene-based copolymer of poly[{9,9-dioctyl-2,7-divinylene-fluorenylene-alt-co-{2-methoxy-5-(2-ethylhexyloxy)-1,4-phenyene}] (PFOPV), which is a solution-processable, non-doped, high-molecular-weight material exhibiting RISC characteristics. A systematical magneto-electroluminescence study joint by time-resolved spectra revealed that charge transfer (CT) states would be generated between PFO and MEH-PPV components of PFOPV, and triplet CT states can participate in RISC process and contribute significantly to the emission. The PFOPV device shows excellent EL performance with EL efficiency of 12.7 cd/A and EQE of 2.2%, which is about 10–15 times and 2–4 times higher than those of PFO (0.9 cd/A, 0.63%) and MEH-PPV (1.2 cd/A, 1.1%) homopolymer devices, respectively.

A comprehensive study of the electrical and optical performance of white polymer light-emitting diodes (PLEDs) based on blends of polyfluorene (PFO) and poly (2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV) is reported in this paper. MEH-PPV concentration was varied from 0 to 15 wt.%. Maximum luminance and current efficiency was obtained at 2.0 wt.% of MEH-PPV. To understand the origin of this enhancement, electrical and emission properties of the blends were investigated over the entire range of MEH-PPV concentration. Charge carrier mobility was estimated using an electroluminescent transient technique (ELT) which was found to be increased at the lower concentrations of MEH-PPV, however, at higher concentration it was lower than that of pristine PFO.The highest carrier mobility of 2.6 × 10 −5 cm 2 v −1 s −1 was observed at 1.2 wt.% MEH-PPV in PFO. Fowler–Nordheim (F-N) model was used to estimate the potential barrier height at anode interface. It was found that the blending with MEH-PPV reduced the hole injection barrier in the PLEDs up to 5.0 wt.% of MEH-PPV. At concentrations greater than 5.0 wt.%, barrier values started increasing again. Correlating these properties with the current density-voltage curves of PLED, it was observed that current density in the device increased up to 5.0 wt.% of MEH-PPV, this was in good agreement with the behavior of barrier height with MEH-PPV concentration. Therefore, it was inferred that reduction in the barrier height is the dominant effect in improving the luminance of blend based PLEDs. However, it was also observed that maximum current efficiency (1.92 cd/A) occurred at 2.0 wt.% of MEH-PPV blend in PFO with Commission Internationale de l’Enclairage (CIE) coordinates close to white light (0.33, 0.33). This meant that emissive characteristics of the blends were also changing with wt.% of MEH-PPV. To investigate this, photophysical properties, photoluminescence (PL) and photoluminescence quantum efficiency (PLQE) of the binary blends were also studied. It was observed that blending lead to lower PLQE and hence would lead to decrease in the current efficiency with MEH-PPV wt.%, if energy transfer from host to guest was the only mechanism for exciton formation in blend based PLEDs. However, comparing the electroluminescence (EL) and PL behavior of blends, enhancement in current efficiency was observed due to direct excitation of MEH-PPV in PLEDs. These two opposite effects, reduction in PLQE of the blend and direct excitation of MEH-PPV, resulted in best current efficiency of PLED at 2.0 wt.%.

A novel benzoxazine-containing temperature T -sensitive fluorescent polyfluorenes (BluePF-BZ) had been prepared. A benzoxazine monomer (BHPF-paa) was firstly synthesized with 9,9-Bis(4-hydroxyphenyl)fluorene, propargylamine and paraformaldehyde through Mannich condensation reaction. The as-prepared BHPF-paa was then incorporated into the preparation of polyfluorenes, and the main-chain BluePF-BZ could finally be obtained. The structures of the obtained monomer and polyfluorenes were characterized by 1 H NMR and FTIR. The BluePF-BZ was finally incorporated into epoxy resin (E44 + D230) to fabricate the T -sensitive material. The thermal stability, optical stability, and T -sensitive fluorescent properties of BluePF-BZ/E44 + D230 were investigated. The BluePF-BZ/E44 + D230 system showed high spectral thermal stability and reversible T -sensitive fluorescent response in relative high temperature (>433 K). To the best of our knowledge, this is the first report about the T -sensitive fluorescent property of PF. Its mechanism of T -sensitive fluorescent property was also studied by comparative experiment and molecular simulation.

Highly efficient and stable blue quantum-dot light-emitting diodes (QD-LEDs) have been realized by using poly (9,9-bis(N-(2′-ethylhexyl)-carbazole-3-yl)-2,7-fluorene) (PFCz) as hole-transporting layers (HTLs). Due to the carbazole units as substituents at the 9-position of polyfluorene, PFCz shows higher hole mobility and better electrochemical stability than poly (N-vinlycarbazole) (PVK). As a result, the maximum current efficiency (CE) and external quantum efficiency (EQE) of the blue QD-LEDs increased from 4.32 cd A−1 to 7.9% for PVK HTL to 7.38 cd A−1 and 12.61% for PFCz HTL, respectively. Furthermore, the PFCz-based blue QD-LED exhibited lower turn-on voltage and longer device lifetime than the PVK-based device. The improvement performance of blue QD-LED should be attributed to the conjugated fluorene backbone and the substituents of the carbazole active sites, thus enhancing hole mobility and electrochemical stability. This result demonstrates that polyfluorenes with pendent carbazole groups is a promising hole-transporting materials for improving performance of blue QD-LEDs.

It is an important challenge to develop a chemosensor for trace uranyl ion in an aqueous medium for sustainable development of nuclear energy and environmental conservation. A conjugated fluorescent polymer sensor P2 based on amidoxime groups and polyfluorene, which showed good hydrophilous resulting adequate contact with uranyl ions and selectivity and sensitivity even in the presence of other metal ions in DMA/H2O (v/v = 20:80, pH = 6.0) solution, for uranyl ion was designed and prepared in this work. And it possesses good thermal stability and a larger Stokes shift (108 nm). Importantly, the fluorescence quenching occurred when P2 combining uranium. It had a good linear relationship with UO22+ concentration in the range of 10 to 200 nM with a fairly low LOD 7.4 × 10−9 M. Interaction properties between the sensor P2 and UO22+ and the fluorescent mechanism were investigated by density functional theory (DFT). More importantly, the sensor can be successfully used for the detection of uranyl ion in environmental solutions. This work suggests that conjugated fluorescent polymer with amidoxime groups will be a prospective sensor of uranyl ion in the environmental sample.

An innovative gas sensor based on Forster Resonance Energy Transfer (FRET) has been developed. It comprises the optimization of thin blend films composed of a conjugated semiconducting polymer (host) and a conveniently chosen pH indicator dye (guest) as sensing agent for acid vapors. Spectroscopic characterization of the films demonstrates that upon exposure to HCl gas, quenching of the polymer emission due to energy transfer process is enlarged. Hence, the dramatic spectral change experienced by the dye in acid atmospheres even at low concentration constitute the principle to achieve a quantitative and sensitive detector using the Forster mechanism modulation of the polymer fluorescence as transduction signal. At low and moderate acid concentration, the detector shows relatively fast response and repeatability after consecutive exposure-recovery cycles, whilst these features wipe away at higher acid vapor contents. The concentration dependence of the fluorescence can be described by an appropriate model that takes into account resonant and non-resonant contributions to the observed photoluminescence.

Two novel polyfluorene-based blue-light emitting copolymers consisting of aromatic carbazole or dibenzothiophene- S , S -dioxide (SO) moiety in side chain are designed and synthesized based on a palladium-catalyzed Suzuki polymerization. The UV–vis absorption, photoluminescence characteristics and wide-angle X-ray diffraction measurements of the resulting copolymers demonstrate that the incorporation of such aromatic units can induce the formation of the β -phase. The resulting copolymers consisting of aromatic units exhibit improved electroluminescence properties relative to the pristine PFO film. A maximum luminous efficiency of 2.25 cd A −1 with Commission Internationale de l’Eclairage coordinates of (0.17, 0.09) is obtained from the light-emitting device based on the copolymer consisting of SO unit (PFO-SO). Device based on copolymer PFO-SO also exhibits stable electroluminescent spectra and relatively low roll-off of luminous efficiency at high current densities. These observations indicate that the incorporation of aromatic moiety in side chain is a promising strategy to obtain stable blue-light-emitting polyfluorenes with enhanced efficiency.

We investigated the effect of blending of a bulky copolymer on the hole transport properties of poly (9,9-dihexyl fluorenyl-2,7-diyl)(PFO) thin films (∼120 nm) at different temperatures by obtaining the current density-voltage measurement. The poly (phenylenevinylene) based copolymer ‘‘Super Yellow” (SY) has been used as a blending component. Such polymer blending matrix is useful as it combines the host polymer (PFO) with the guest polymer of bulky side groups where pi-pi stacking is hindered by bulky side groups. This makes polyflorene much interesting and versatile material for lighting application. It has been found that the current density decreases on blending for a given applied bias. We demonstrated that the current conduction mechanism is bulk limited. It has been analyzed by trapped charge limited currents (TCLC) with electric field. We conclude that the relatively low hole mobility in blends as compared to pristine PFO would result due to increase in the pi-pi stacking distance and disorder.

The photophysical properties of conjugated polymers are sensitive to the environment; hence they can be used as probe for local interactions. Here we report on the effect of a ferroelectric polymer in the photoluminescence of a conjugated polymer and show that the local electric field, created by the ferroelectric polymer, induces a photoluminescence quenching, translated into a reduction of the fluorescence intensity and lifetime. Blends and bi-layer systems were studied, with the blends showing a more pronounced effect.

This paper reports the multifunctional responsive fluorescence chemosensory phenomena of two terpyridine-functionalized conjugated polyfluorenes (PFs), poly[2,7-(9,9-dihexylfluorene)- alt -4′-((4-[N,N-(4-phenyl)amino]styryl)phenyl)-2,2′:6′,2″-terpyridine] ( P1 ) and poly[2,7-(9,9-dihexylfluorene)- alt -4′-phenyl-2,2′:6′,2″-terpyridine] ( P2 ), which were exposed to solvents, metal ions, and protons through Suzuki polymerization. Compared with P2 , P1 exhibited enhanced sensing ability that resulted from efficient interactions between the specific triphenylamine-linked terpyridine units with protons and metal ions. P1 and P2 both showed high sensitivity toward Cu 2+ , with the Stern-Volmer constants of 2.30 × 10 5 M −1 and 1.05 × 10 5 M −1 , respectively. Because of the very high stability constants of the CN − –Cu 2+ complexes, the fluorescence of P1 and P2 solutions that were quenched by Cu 2+ recovered upon addition of trace CN − , with a detection limit as low as 3.7 × 10 −6 M −1 and 5.2 × 10 −6 M −1 for P1 and P2 , respectively. P1 showed fluorescence quenching when pH decreased from 5.0 to 1.0; however, a pH of 13.0 had little effect on fluorescence intensity. Our results suggest that P1 is a promising material for chemosensory applications.

A new kind of single triple-color hyperbranched polymer PF-Ir(ppy) 2 (pytzph)m-Ir(piq) 2 (pytzph)n was designed and synthesized, in which green and red iridium(III) complexes acted as cores and blue polyfluorene acted as backbone. PF-Ir(ppy) 2 (pytzph)m-Ir(piq) 2 (pytzph)n (m = 5, n = 5 and m = 25, n = 5) had higher quantum efficiency than PF-Ir(piq) 2 (pytzph)5. The energy transfer from green core bis(2-phenylpyridine)[3-(2-pyridyl)-5-phenyl-1,2,4-triazole]iridium(III) [Ir(ppy) 2 (pytzph)] with high triplet energy level (E T = 2.58 eV) to red core bis(1-phenylisoquinolinato)[3-(2-pyridyl)-5-phenyl-1,2,4-triazole]iridium(III) [Ir(piq) 2 (pytzph)] (E T = 2.12 eV) could realize by intermediate poly(9,9-dioctylfluorene) (PF) segments. A typical single emitting-layer device with the configuration of ITO/PEDOT:PSS (40 nm)/PF-Ir(ppy) 2 (pytzph)m-Ir(piq) 2 (pytzph)n (80 nm)/TPBi (40 nm)/LiF (0.8 nm)/Al (100 nm) was fabricated. Among the white polymers, PF-Ir(ppy) 2 (pytzph)5-Ir(piq) 2 (pytzph)5 exhibited excellent electroluminescent properties with a Commission Internationale Ed I'eclairage (CIE) coordinate of (0.32, 0.34) and a maximum luminous efficiency of 11.49 cd/A.

We report enhanced color purity of hybrid organic-inorganic light emitting diode based on polyfluorene-CdSe/ZnS quanum dot (QD) blend as emissive layer. Effect on structural, optical and electrical properties of different doping concentration (0–100 wt.%) of QD in polyfluorene (PFO) was studied. Photoluminescence and electroluminescence spectra confirm the β-formation of PFO by incorporation of CdSe/ZnS QD. Photoluminescence (PL) of blend film was also compared with another method based on one dimensional photonic band gap (1D-PBG) structure that has been used for color purity. In both the cases, that is, QD doped device and 1D-PBG based structures the narrowing of PL spectra was observed. But the fabrication of QD-doped device for color purity is easier than fabricating 1D-PBG structure using multilayer dielectric coating. The present study might find application for QD based color displays, where color purity is an important requirement.

A series of novel star-shape like white polymers were synthesized by employing the benzene as the core, and incorporating different amount of bis (4-methoxyphenyl) maleimide guest onto the side-chain of the polyfluorene (PF) arm host. Due to the large feed ratio of core, such a construction strategy could efficiently avoid or suppress the formation of linear PF which always existed in the previous star-like polymers employing guest as core. When applied to the single emitting layer devices fabricated by solution spin-coating method, the efficiency of the devices enhanced gradually with the amount of guest increasing from 0.01% to 2%. The device performance was further improved substantially by annealing at 140 °C. A typical device base on P1 containing 1% dopant exhibited maximal luminous efficiency of 6.13 cd/A. Interestingly, the increase of efficiency is not originated from the self-dopant effect of α or β crystalline phase, which was always produced by thermal treatment at 120 °C in linear or previous star-like polyfluorenes. Morphology analysis disclosed that annealing made the polymeric molecules stack become closer, consequently resulting in a more effectively charge transfer and energy transfer from host to guest. As a result, the compact molecular stacking of the star-shape like polymers should be responsive for the high efficiency of annealed devices. The results would be conducive to design new star-shape like polymers with more arms, and improve the performance of white devices.

In this study, a sulfonated polyfluorene, poly-[9,9-bis(3-propylamide-2-methylpropyl sulfonic acid) fluorene]-co-(4,4′-diphenyl) (PFDBSO3H), was synthesized and characterized. The poly(3,4-ethylenedioxythiophene) (PEDOT) water dispersions with PFDBSO3H as a template were synthesized and investigated. Results showed that conductivity increment of PEDOT film was observed when the semiconductor, PFDBSO3H, was used as the template and doping agent, and square resistance of the PEDOT film decreased as the amount of PFDBSO3H increased in the template. This increase of conductivity of the PEDOT film was mainly attributed to the semiconductive nature of PFDBSO3H template and better phase separation between PFDBSO3H and poly(styrenesulfonate) (PSS). The PEDOT film with PFDBSO3H template showed good transparency in the 400–800-nm wavelength region and good electrochemical stability. However, a slight decrease in thermal stability was observed.

Fluorescence quenching of polyfluorene-based polymer (PFO-BPy) attached to single-wall carbon nanotubes (SWNT) has been investigated by means of fluorescence and transient absorption spectroscopy. Fluorescence of SWNT/PFO-BPy complex suspension in chlorobenzene decays nonexponentialy on a time scale from several to several hundreds of picoseconds, and experiences slower depolarization if compared with free polymer in solution. We attribute the slowly quenched and more polarized fluorescence to the polymer tail segments that are not in direct contact with the SWNT. Polymer fluorescence in SWNT/PFO-BPy solid films is quenched about 10 times faster than in suspensions. The initial excited state quenching in films occurs with a 2.3 ps time constant, which we attribute to the polymer chains intimately attached to the SWNT. Slow changes of the spectroscopic properties of the SWNT/PFO-BPy suspensions with time revealed that their aging is associated with the desorption of polymers from SWNT, increasing their tendency to aggregate.

A series of triple-color hyperbranched polymers based on poly(9,9-dioctylfluorene) (PF) were designed and synthesized, in which phosphorescent tris(1-phenylisoquinoline)iridium(Ш) (Ir(piq)3) acts as red core and poly[(9,9-dioctylfluorene-2,7-diyl)-alt-(benzo[2,1,3]thiadiazol-4,7-diyl)] (PFBT) is inserted as green-emission segment. The synthesized polymers have good thermostability, film forming ability and high fluorescence quantum yield. By tuning the contents of red core and green-emission segment, the optimized triple-color hyperbranched polymer is acquired, named PF-BT250-Ir(piq)325. Furthermore, the PF-BT250-Ir(piq)325 is utilized as single emission layer in white polymer light emitting diode with the configuration of ITO/PEDOT:PSS (50 nm)/PF-BT250-Ir(piq)325 (80 nm)/TPBI (40 nm)/LiF (1 nm)/Al (100 nm). The diode exhibits a maximum luminous efficiency of 1.60 cd/A, a maximum luminance of 3267 cd/m2 and the Commission Internationale de l’Eclairage coordinate of (0.32, 0.34) very close to the pure white point of (0.33, 0.33).

We report that the supramolecular liquid-crystal (LC) physical gel can be formed through the fibrous self-assembly of the polyfluorene-based π-conjugated polymer, poly(9,9-dioctylfluorene-alt-benzothiadiazole) (F8BT), in twisted nematic LC system for the first time. With the utility of alignment layers, the F8BT molecules can be aligned and formed the LC physical gels with the formation of self-assembled supramolecular structures in the twisted nematic LCs. In contrast to conventional LC physical gels, the presence of anisotropic π-conjugated structure makes the twisted nematic LC system exhibit excellent electro-optical properties of driving voltage reduction and contrast ratio enhancement owing to the conjugated polymer having a high π-electron delocalization degree which can efficiently drive LC molecules in much lower operating voltages. The self-assembled supramolecular network has revealed the potential for applying in various LC display devices with the ability of improving their electro-optical performance.

Polyfluorene copolymers containing 33 mol% of 2,5-difluoro-1,4-phenylene units and other comonomers comprising chargetransporting triphenylamine, carbazole, and 1,8-naphthalimide groups were synthesized by the Suzuki polycondensation under microwave irradiation. On heating the obtained copolymers to 180 °C, their photoluminescence spectra remain stable. The best sample herein obtained provided the OLED brightness of 2830 cd m–2, current efficiency of 0.5 cd A–1 and CIE coordinates of x = 0.168 and y = 0.228.

Vibrational effects are crucial for optimizing the performances of phosphorescent Ir compounds as emitters in OLEDs. But, usually purely electronic spin–orbit coupling, where the coupling remains unchanged by vibrational motion, is taken into account as the sole mechanism for mixing singlets and triplets states, and mechanisms that depend on molecular vibrations are largely overlooked. Here I investigate a doubly doped system with iridium(III)tris(2-(4-tolyl)phenylpyridine [Ir(mppy)3] as assistant dopant, and bis(2–(9,9–dihexylfluorenyl)–1–pyridine)–(acetylacetonate) iridium(III) [Ir((dhfpy)2(acac)] as phosphorescent emitter dopant blended into a mixed phase polyfluorene matrix. The electroluminescence of the fully solution–processed single–layer devices show a well–resolved structured emission of the triplet emitter that can be interpreted in terms of Franck–Condon activity in the presence of the assistant dopant. Changes in the local environment of the emitter brought about by modifying the doping levels lead to different ratios of these vibronic bands, whose balanced combination along with blue fluorescent emission from the polymer host enable white electroluminescence with CIE coordinates (0.37, 0.33) in a simple device structure. Furthermore, the introduction of the assistant dopant boots significantly device performance.