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Polymers containing π-conjugated segments are a diverse group of large molecules with semiconducting and emissive properties, with strong potential for use as active layers in Organic Light-Emitting Diodes (OLEDs). Stable blue-emitting materials, which are utilized as emissive layers in solution-processed OLED devices, are essential for their commercialization. Achieving balanced charge injection is challenging due to the wide bandgap between the HOMO and LUMO energy levels. This study examines the optical and photophysical characteristics of blue-emitting polymers to contribute to the understanding of the fundamental mechanisms of color purity and its stability during the operation of OLED devices. The investigated materials are a novel synthesized lab scale polymer, namely poly[(2,7-di(p-acetoxystyryl)-9-(2-ethylhexyl)-9H-carbazole-4,4′-diphenylsulfone)-co-poly(2,6-diphenylpyrydine-4,4′-diphenylsulfone] (CzCop), as well as three commercially supplied materials, namely Poly(9,9-di-n-octylfluorenyl-2,7-diyl) (PFO), poly[9,9-bis(2′-ethylhexyl) fluorene-2,7-diyl] (PBEHF), and poly (9,9-n-dihexyl-2,7-fluorene-alt-9-phenyl-3,6-carbazole) (F6PC). The materials were compared to evaluate their properties using Spectroscopic Ellipsometry, Photoluminescence, and Atomic Force Microscopy (AFM). Additionally, the electrical characteristics of the OLED devices were investigated, as well as the stability of the electroluminescence emission spectrum during the device's operation. Finally, the determined optical properties, combined with their photo- and electro-emission characteristics, provided significant insights into the color stability and selectivity of each material. [ABSTRACT FROM AUTHOR]

In pursuing sustainable technologies, organic electronic-based materials have witnessed remarkable progress, with polyfluorene (PF) among the blue light-emitting polymers garnering significant attention. PF, renowned for its remarkable light absorption and exceptional optoelectronic properties, exhibits great potential for various applications including display technologies, solar cells, lasers and transistors. Nonetheless, the diverse phases in PF significantly affect the performance of optoelectronic devices, predominantly due to the coexistence of different conformations in thin films, while promising, PF confronts hurdles related to stability and degradation during operation, leading to spectral changes and colour purity issue. Since the early 1990s, various studies have been devoted by researchers to determine the chemical changes in the PF chain and its functional groups after being subjected to different types of degradation with the aim of controlling and retarding the decomposition process. Another alternative strategy is to promote the formation of β-phase in PF, which is characterised by well-ordered conformation. This review aims to provide a comprehensive overview of PF degradation behaviour, modes and mechanisms. Various approaches to delay and suppress PF degradation are discussed. Meanwhile, the role of the β-phase in suppressing PF degradation and enhancing optoelectronic applications has also been highlighted. Thus, scientists are diligently attempting to enhance the formation and stability of the β-phase to improve the performance of optoelectronic applications. [ABSTRACT FROM AUTHOR]

Polymers containing π-conjugated segments are a diverse group of large molecules with semiconducting and emissive properties, with strong potential for use as active layers in Organic Light-Emitting Diodes (OLEDs). Stable blue-emitting materials, which are utilized as emissive layers in solution-processed OLED devices, are essential for their commercialization. Achieving balanced charge injection is challenging due to the wide bandgap between the HOMO and LUMO energy levels. This study examines the optical and photophysical characteristics of blue-emitting polymers to contribute to the understanding of the fundamental mechanisms of color purity and its stability during the operation of OLED devices. The investigated materials are a novel synthesized lab scale polymer, namely poly[(2,7-di(p-acetoxystyryl)-9-(2-ethylhexyl)-9H-carbazole-4,4′-diphenylsulfone)-co-poly(2,6-diphenylpyrydine-4,4′-diphenylsulfone] (CzCop), as well as three commercially supplied materials, namely Poly(9,9-di-n-octylfluorenyl-2,7-diyl) (PFO), poly[9,9-bis(2′-ethylhexyl) fluorene-2,7-diyl] (PBEHF), and poly (9,9-n-dihexyl-2,7-fluorene-alt-9-phenyl-3,6-carbazole) (F6PC). The materials were compared to evaluate their properties using Spectroscopic Ellipsometry, Photoluminescence, and Atomic Force Microscopy (AFM). Additionally, the electrical characteristics of the OLED devices were investigated, as well as the stability of the electroluminescence emission spectrum during the device’s operation. Finally, the determined optical properties, combined with their photo- and electro-emission characteristics, provided significant insights into the color stability and selectivity of each material.

Thin films of conjugated polymer and enzyme can be used to unravel the interaction between components in a biosensor. Using artificial neural networks (ANNs) improves data interpretability and helps construct models with great capacity for classifying and processing information. The present work used kinetic data from the catalytic activity of urease immobilized in different conjugated polymers to create ANN models using time, substrate concentration, and absorbance as input variables since the models had absorbance in a posterior instant as output value to explore the predictivity of the ANNs. The performance of the models was evaluated by Pearson's correlation coefficient (ρ) and mean squared error (MSE) values. After the learning process, a series of new experiments were performed to verify the generality of the models. As the main results, the best ANN model presented 0.9980 and 3.0736 × 10–5 for ρ and MSE, respectively. For the simulation step, intermediary values of substrate concentration were used. The mean absolute percentage error (MAPE) values were 3.34, 3.07, and 3.78 for 12 mM, 22 mM, and 32 mM concentrations, respectively. Overall, with the simulations, it was possible to ascertain the interpolatory capacity of the model, which has a learning mechanism based on absorbance and time as variables. Thus, the potential of ANNs would be in their use in pre-evaluations, helping to determine the substrate concentration at which there is higher catalytic activity or in determining the linear range of the sensor. [ABSTRACT FROM AUTHOR]

We synthesized a fluorene‐bithiophene co‐polymer with chiral side chains (cPFT2) and investigated its chiroptical properties via synchotronradiation circular dichroism. We observed that thin films of the polymer display an intense circular dichroism (CD) upon annealing, which is of opposite handedness to the CD reported for similar polyfluorenes bearing the same enantiomeric chiral side chain. We then contrast the properties of this polymer with chiral side chain fluorene homopolymer (cPF) and observe large differences in their thin film morphology. Using photoluminescence spectroscopy, we uncover evidence of polymer chain bending in cPFT2, which is further supported by theoretical calculations, and propose an explanation for the observed inverted optical activity. [ABSTRACT FROM AUTHOR]

The use of conjugated polymers (CPs) and metallic nanoparticles is an interesting way to form nanocomposites with improved optical properties. For instance, a nanocomposite with high sensitivity can be produced. However, the hydrophobicity of CPs may hamper applications due to their low bioavailability and low operability in aqueous media. This problem can be overcome by forming thin solid films from an aqueous dispersion containing small CP nanoparticles. So, in this work we developed the formation of thin films of poly(9,9-dioctylfluorene-co-3,4-ethylenedioxythiophene) (PDOF-co-PEDOT) from its natural and nano form (NCP) from aqueous solution. These copolymers were then blended in films with triangular and spherical silver nanoparticles (AgNP) for future applicability as a SERS sensor of pesticides. TEM characterization showed that the AgNP were adsorbed on the NCP surface, forming a nanostructure with an average diameter of 90 nm (value according to that obtained by DLS) and with a negative potential zeta. These nanostructures were transferred to a solid substrate, forming thin and homogeneous films with different morphology of PDOF-co-PEDOT films, as observed by atomic force microscopy (AFM). XPS data demonstrated the presence of the AgNP in the thin films, as well as evidence that films with NCP are more resistant to the photo-oxidation process. Raman spectra showed characteristic peaks of the copolymer in the films prepared with NCP. It should also be noted the enhancement effect of Raman bands observed on films containing AgNP, a strong indication of the SERS effect induced by the metallic nanoparticles. Furthermore, the different geometry of the AgNP influences the way in which the adsorption between the NCP and the metal surface occurs, with a perpendicular adsorption between the NCP chains and the surface of the triangular AgNP. [ABSTRACT FROM AUTHOR]

A study of cofacially arrayed π-systems is of particular importance for the design of functional materials for efficient long-range intra-chain charge transfer through the bulk semiconducting materials in the layers of photovoltaic devices. The effect of π-stacking between a pair of aromatic rings has been mainly studied in the form of cyclophanes, where aromatic rings are forced into a sandwich-like geometry, which extensively deforms the aromatic rings from planarity. The synthetic difficulties associated with the preparation of cyclophane-like structures has prevented the synthesis of many examples of their multi-layered analogues. Moreover, the few available multi-layered cyclophanes are not readily amenable to the structural modification required for the construction of D–spacer–A triads needed to explore mechanisms of electron and energy transfer. In this review, we recount how a detailed experimental and computational analysis of 1,3-diarylalkanes led to the design of a new class of cofacially arrayed polyfluorenes that retain their π-stacked structure. Thus, efficient synthetic strategies have been established for the ready preparation of monodisperse polyfluorenes with up to six π-stacked fluorenes, which afford ready access to D–spacer–A triads by linking donor and acceptor groups to the polyfluorene spacers via single methylenes. Detailed 1H NMR spectroscopy, X-ray crystallography, electrochemistry, and He(I) photoelectron spectroscopy of F2–F6 have confirmed the rigid cofacial stacking of multiple fluorenes in F2–F6, despite the presence of rotatable C–C bonds. These polyfluorenes (F2–F6) form stable cation radicals in which a single hole is delocalized amongst the stacked fluorenes, as judged by the presence of intense charge-resonance transition in their optical spectra. Interestingly, these studies also discern that delocalization of a single cationic charge could occur over multiple fluorene rings in F2–F6, while the exciton is likely localized only onto two fluorenes in F2–F6. Facile synthesis of the D–spacer–A triads allowed us to demonstrate that efficient triplet energy transfer can occur through π-stacked polyfluorenes; the mechanism of energy transfer crosses over from tunneling to hopping with increasing number of fluorenes in the polyfluorene spacer. We suggest that the development of rigidly held π-stacked polyfluorenes, described herein, with well-defined redox and optoelectronic properties provides an ideal scaffold for the study of electron and energy transfer in D-spacer-A triads, where the Fn spacers serve as models for cofacially stacked π-systems. [ABSTRACT FROM AUTHOR]

We compare the pH sensing performance of non-functionalized carbon nanotubes (CNT) field-effect transistors (p-CNTFET) and CNTFET functionalized with a conjugated polyfluorene polymer (labeled FF-UR) bearing urea-based moieties (f-CNTFET). The devices are electrolyte-gated, PMMA-passivated, 5 µm-channel FETs with unsorted, inkjet-printed single-walled CNT. In phosphate (PBS) and borate (BBS) buffer solutions, the p-CNTFETs exhibit a p-type operation while f-CNTFETs exhibit p-type behavior in BBS and ambipolarity in PBS. The sensitivity to pH is evaluated by measuring the drain current at a gate and drain voltage of −0.8 V. In PBS, p-CNTFETs show a linear, reversible pH response between pH 3 and pH 9 with a sensitivity of 26 ± 2.2%/pH unit; while f-CNTFETs have a much stronger, reversible pH response (373%/pH unit), but only over the range of pH 7 to pH 9. In BBS, both p-CNTFET and f-CNTFET show a linear pH response between pH 5 and 9, with sensitivities of 56%/pH and 96%/pH, respectively. Analysis of the I–V curves as a function of pH suggests that the increased pH sensitivity of f-CNTFET is consistent with interactions of FF-UR with phosphate ions in PBS and boric acid in BBS, with the ratio and charge of the complexed species depending on pH. The complexation affects the efficiency of electrolyte gating and the surface charge around the CNT, both of which modify the I–V response of the CNTFET, leading to the observed current sensitivity as a function of pH. The performances of p-CNTFET in PBS are comparable to the best results in the literature, while the performances of the f-CNTFET far exceed the current state-of-the-art by a factor of four in BBS and more than 10 over a limited range of pH in BBS. This is the first time that a functionalization other than carboxylate moieties has significantly improved the state-of-the-art of pH sensing with CNTFET or CNT chemistors. On the other hand, this study also highlights the challenge of transferring this performance to a real water matrix, where many different species may compete for interactions with FF-UR. [ABSTRACT FROM AUTHOR]

This work describes the development and characterization of fluorescent nanocomposite hydrogels, with high swelling and absorption capacity, and prepared using a green protocol. These fluorescent materials are obtained by incorporating, for the first time, polyfluorenes-based nanoparticles with different emission bands—poly[9,9-dioctylfluorenyl-2,7-diyl] (PFO) and poly[(9,9-di-n-octylfluorenyl-2,7-diyl)-alt-(1,4-benzo-{2,1,3}-thiadiazole)] (F8BT)—into a three-dimensional polymeric network based on polyacrylamide. To this end, two strategies were explored: incorporation of the nanoparticles during the polymerization process (in situ) and embedment after the hydrogel formation (ex situ). The results show that the combination of PFO nanoparticles introduced by the ex situ method provided materials with good storage stability, homogeneity and reproducibility properties, allowing their preservation in the form of xerogel. The fluorescent nanocomposite hydrogels have been tested as a transportable and user-friendly sensing platform. In particular, the ability of these materials to specifically detect the enzyme alkaline phosphatase (ALP) has been evaluated as a proof-of-concept. The sensor was able to quantify the presence of the enzyme in an aqueous sample with a response time of 10 min and LOD of 21 nM. Given these results, we consider that this device shows great potential for quantifying physiological ALP levels as well as enzyme activity in environmental samples. [ABSTRACT FROM AUTHOR]

Water‐soluble π‐conjugated polyfluorene bearing 6‐N1‐cytosinehexyl and 6‐trimethylammoniumhexyl bromide side chains, namely polymer‐1, was synthesized by Suzuki polycondensation. The absorption onset wavelength (λonset) of the polymer was longer than that of the monomer and confirmed the presence of the π‐conjugated system along the polymer chain. The cyclic voltammetry and UV–vis analyses showed that the highest occupied molecular orbital and lowest unoccupied molecular orbital energy levels of the polymer were −5.5 and −2.6 eV, respectively. The photoluminescence (PL) intensity of the polymer decreased with increasing DNA chain length (m) upon adding (TTAGGG)m (T = thymine, A = adenine, and G = guanine; m = 2, 4, 6, and 8), indicating that the polymer could detect telomere DNA chain lengths with higher precision than previously reported DNA sensors. Similarly, the PL intensity decreased with the addition of nucleosides. Photoinduced charge transfer in the complex between the polymer and DNA or nucleoside played an important role in the PL response of the polymer toward analytes. The sensing behavior was analyzed using the Stern–Volmer and Benesi–Hildebrand methods. [ABSTRACT FROM AUTHOR]

Conjugated polymers (CPs) are an intriguing material with which to build fluorescent Cr2O72− sensors with excellent sensitivity, but they often lack specific recognition groups. In this study, several typical amino acids with N and O atom-identifying groups were incorporated into fluorene, and then six polyfluorene derivatives were synthesized using electrochemical polymerization. Compared to other cations and anions, all of these amino acid-functionalized polyfluorenes have good selectivity towards Cr2O72− and enable ultra-trace responses with detection thresholds at pM or even fM level.

Anion exchange membrane water electrolysis (AEMWE) is currently paying attention as a new hydrogen (H2) production method since it can operate at high current densities using inexpensive nonnoble metal catalysts. However, the significant problems of AEMs, including their insufficient anion conductivity and alkaline stability, prevent the practical usage of AEMWE. We show a novel anion conductive polymer, alkyl trimethylammonium‐substituted polyfluorene (TMA‐PF), bearing no heteroatom bonds in the main chain. The TMA‐PF membrane possesses higher anion conductivity than conventional AEMs due to the increased flexibility and mobility of the alkylammonium side chains of TMA‐PF. The TMA‐PF membrane shows high‐alkaline stability and maintains the initial ion conductivity after immersion in an aqueous NaOH solution (8 mol L−1) at 80°C for 48 h. In the water electrolysis evaluation, the cell using the TMA‐PF membrane exhibits a higher current density (400 mA cm−2 at 2.03 V) than the cell using the conventional AEM at the same potential, indicating that the novel AEM has a high potential to generate H2 effectively. Green hydrogen produced by AEMWE using renewable energy will be an environmentally benign energy source without CO2 emissions. [ABSTRACT FROM AUTHOR]

A polyfluorene containing praseodymium complexes was synthesized with fluorene, phenanthroline, and praseodymium triisopropoxide units by way of the conventional coordination reaction and palladium-catalyzed Suzuki coupling reaction. The composition and structure of the polymers were identified by 1H NMR (nuclear magnetic resonance) spectra. The material is easy to dissolve in most common organic solvents and has high thermal stability, which is beneficial to the device preparation process. Optical characterizations including ultraviolet and visible (UV-vis) absorption spectra, photoluminescence, and electroluminescence of the target polymer were recorded and analyzed to investigate the effects of Pr triisopropoxide. The optoelectronic devices obtained were measured with the configuration ITO/PEDOT:PSS/polymer/TPBi/LiF/Al based on the resulting polymer as an emissive layer. The results show that the praseodymium triisopropoxide complexes in the polymer structure tuned the emission color and improved the performance of the optoelectronic device. Therefore, this technique can provide an inexpensive and straightforward method for the synthesis of lanthanide-complexed copolymer applied in the field of organic optoelectronic materials. A praseodymium (Pr)-bonded polymer with fluorene, phenanthroline, and Pr triisopropoxide in the main chain was synthesized via coordination reaction and Suzuki reaction. The photoluminescence and electroluminescence properties of the polymer were studied to explore the effects of Pr triisopropoxide. The introduction of Pr triisopropoxide into the polymer tuned the emission color and improved the performance of the optoelectronic device. [ABSTRACT FROM AUTHOR]

For the improvement of the electron transporting property of poly(9,9-di- n -octylfluorene) (PFO) as a conventional polymer light-emitting diode material, well-defined triblock copolymers of PFO [number-average molecular weight (M n) ≈ 10 000] with different chain length polystyrene (PSt) (M n ≈ 1000, 2000, and 3000) were synthesized via a combined synthesis strategy of Suzuki–Miyaura reaction, atom transfer radical polymerization, and Steglich coupling reaction. Electron-only devices for homopolymer and triblock copolymers were fabricated by a solution process. It was demonstrated that triblock copolymer (M n,PSt ≈ 2000) after annealing exhibited the highest electron mobility. Thermal, optical, electrochemical and morphological properties were investigated severally and revealed that the microphase separated structure was formed in block copolymers (M n,PSt ≈ 2000, and 3000) after annealing, and the introduction of PSt raised the glass transition temperature (T g) and deepened the lowest unoccupied molecular orbital level. [ABSTRACT FROM AUTHOR]

The use of conjugated polymers (CPs) and metallic nanoparticles is an interesting way to form nanocomposites with improved optical properties. For instance, a nanocomposite with high sensitivity can be produced. However, the hydrophobicity of CPs may hamper applications due to their low bioavailability and low operability in aqueous media. This problem can be overcome by forming thin solid films from an aqueous dispersion containing small CP nanoparticles. So, in this work we developed the formation of thin films of poly(9,9-dioctylfluorene-co-3,4-ethylenedioxythiophene) (PDOF-co-PEDOT) from its natural and nano form (NCP) from aqueous solution. These copolymers were then blended in films with triangular and spherical silver nanoparticles (AgNP) for future applicability as a SERS sensor of pesticides. TEM characterization showed that the AgNP were adsorbed on the NCP surface, forming a nanostructure with an average diameter of 90 nm (value according to that obtained by DLS) and with a negative potential zeta. These nanostructures were transferred to a solid substrate, forming thin and homogeneous films with different morphology of PDOF-co-PEDOT films, as observed by atomic force microscopy (AFM). XPS data demonstrated the presence of the AgNP in the thin films, as well as evidence that films with NCP are more resistant to the photo-oxidation process. Raman spectra showed characteristic peaks of the copolymer in the films prepared with NCP. It should also be noted the enhancement effect of Raman bands observed on films containing AgNP, a strong indication of the SERS effect induced by the metallic nanoparticles. Furthermore, the different geometry of the AgNP influences the way in which the adsorption between the NCP and the metal surface occurs, with a perpendicular adsorption between the NCP chains and the surface of the triangular AgNP.

[Display omitted] • S0 → S1 electron excitation in polyfluorene in most cases is localized in central 8–9 units. • Changing conformation may lead to small changes of effective conjugation length. • Substituents in side radicals do not have a significant effect on the localization of excitation. This study investigates the excited states within oligomeric fluorene compounds containing up to 20 monomer units in various conformations. Furthermore, it explores the impact of donor and acceptor substituents in the side chain. Time-dependent density functional theory (TD-DFT) simulations were conducted at the B3LYP/def2-svp level of theory. Results indicate localized excitation, primarily spanning 8–13 monomer units, irrespective of donor and acceptor substituents. These findings offer insights into charge carrier mobility, electroluminescent properties of polyfluorenes, and facilitate the design of novel materials within this class. [ABSTRACT FROM AUTHOR]

A study of cofacially arrayed π-systems is of particular importance for the design of functional materials for efficient long-range intra-chain charge transfer through the bulk semiconducting materials in the layers of photovoltaic devices. The effect of π-stacking between a pair of aromatic rings has been mainly studied in the form of cyclophanes, where aromatic rings are forced into a sandwich-like geometry, which extensively deforms the aromatic rings from planarity. The synthetic difficulties associated with the preparation of cyclophane-like structures has prevented the synthesis of many examples of their multi-layered analogues. Moreover, the few available multi-layered cyclophanes are not readily amenable to the structural modification required for the construction of D–spacer–A triads needed to explore mechanisms of electron and energy transfer. In this review, we recount how a detailed experimental and computational analysis of 1,3-diarylalkanes led to the design of a new class of cofacially arrayed polyfluorenes that retain their π-stacked structure. Thus, efficient synthetic strategies have been established for the ready preparation of monodisperse polyfluorenes with up to six π-stacked fluorenes, which afford ready access to D–spacer–A triads by linking donor and acceptor groups to the polyfluorene spacers via single methylenes. Detailed 1H NMR spectroscopy, X-ray crystallography, electrochemistry, and He(I) photoelectron spectroscopy of F2–F6 have confirmed the rigid cofacial stacking of multiple fluorenes in F2–F6, despite the presence of rotatable C–C bonds. These polyfluorenes (F2–F6) form stable cation radicals in which a single hole is delocalized amongst the stacked fluorenes, as judged by the presence of intense charge-resonance transition in their optical spectra. Interestingly, these studies also discern that delocalization of a single cationic charge could occur over multiple fluorene rings in F2–F6, while the exciton is likely localized only onto two fluorenes in F2–F6. Facile synthesis of the D–spacer–A triads allowed us to demonstrate that efficient triplet energy transfer can occur through π-stacked polyfluorenes; the mechanism of energy transfer crosses over from tunneling to hopping with increasing number of fluorenes in the polyfluorene spacer. We suggest that the development of rigidly held π-stacked polyfluorenes, described herein, with well-defined redox and optoelectronic properties provides an ideal scaffold for the study of electron and energy transfer in D-spacer-A triads, where the Fn spacers serve as models for cofacially stacked π-systems.

We compare the pH sensing performance of non-functionalized carbon nanotubes (CNT) field-effect transistors (p-CNTFET) and CNTFET functionalized with a conjugated polyfluorene polymer (labeled FF-UR) bearing urea-based moieties (f-CNTFET). The devices are electrolyte-gated, PMMA-passivated, 5 µm-channel FETs with unsorted, inkjet-printed single-walled CNT. In phosphate (PBS) and borate (BBS) buffer solutions, the p-CNTFETs exhibit a p-type operation while f-CNTFETs exhibit p-type behavior in BBS and ambipolarity in PBS. The sensitivity to pH is evaluated by measuring the drain current at a gate and drain voltage of −0.8 V. In PBS, p-CNTFETs show a linear, reversible pH response between pH 3 and pH 9 with a sensitivity of 26 ± 2.2%/pH unit; while f-CNTFETs have a much stronger, reversible pH response (373%/pH unit), but only over the range of pH 7 to pH 9. In BBS, both p-CNTFET and f-CNTFET show a linear pH response between pH 5 and 9, with sensitivities of 56%/pH and 96%/pH, respectively. Analysis of the I–V curves as a function of pH suggests that the increased pH sensitivity of f-CNTFET is consistent with interactions of FF-UR with phosphate ions in PBS and boric acid in BBS, with the ratio and charge of the complexed species depending on pH. The complexation affects the efficiency of electrolyte gating and the surface charge around the CNT, both of which modify the I–V response of the CNTFET, leading to the observed current sensitivity as a function of pH. The performances of p-CNTFET in PBS are comparable to the best results in the literature, while the performances of the f-CNTFET far exceed the current state-of-the-art by a factor of four in BBS and more than 10 over a limited range of pH in BBS. This is the first time that a functionalization other than carboxylate moieties has significantly improved the state-of-the-art of pH sensing with CNTFET or CNT chemistors. On the other hand, this study also highlights the challenge of transferring this performance to a real water matrix, where many different species may compete for interactions with FF-UR.

This work describes the development and characterization of fluorescent nanocomposite hydrogels, with high swelling and absorption capacity, and prepared using a green protocol. These fluorescent materials are obtained by incorporating, for the first time, polyfluorenes-based nanoparticles with different emission bands—poly[9,9-dioctylfluorenyl-2,7-diyl] (PFO) and poly[(9,9-di-n-octylfluorenyl-2,7-diyl)-alt-(1,4-benzo-{2,1,3}-thiadiazole)] (F8BT)—into a three-dimensional polymeric network based on polyacrylamide. To this end, two strategies were explored: incorporation of the nanoparticles during the polymerization process (in situ) and embedment after the hydrogel formation (ex situ). The results show that the combination of PFO nanoparticles introduced by the ex situ method provided materials with good storage stability, homogeneity and reproducibility properties, allowing their preservation in the form of xerogel. The fluorescent nanocomposite hydrogels have been tested as a transportable and user-friendly sensing platform. In particular, the ability of these materials to specifically detect the enzyme alkaline phosphatase (ALP) has been evaluated as a proof-of-concept. The sensor was able to quantify the presence of the enzyme in an aqueous sample with a response time of 10 min and LOD of 21 nM. Given these results, we consider that this device shows great potential for quantifying physiological ALP levels as well as enzyme activity in environmental samples.

In this study, the authors report a series of conjugated block copolymers, PF‐b‐Piso comprising poly[2,7‐(9,9‐dihexylfluorene)] (PF), and poly(pendent isoindigo) (Piso) for polymer electret in the photonic field‐effect transistor (FET) memory device. The optical properties, surface morphology, and molecular organization of these BCPs are investigated systematically. Accordingly, Piso with absorption in the Ultraviolet C range (UVC, 200–280 nm) possibly rendered the device with a multiband photoresponse, and a good memory performance is achieved by optimizing the polymer composition. Therefore, the memory device comprising PF‐b‐Piso could perform a high current contrast of 106 to 405 nm light and 105 to 254 nm light over 104 s. In addition, a current contrast of 104 and 102 is achieved in response to 650 and 530 nm light, and this phenomenon can be attributed to the charge transfer between channel and memory layers. The experimental results indicate that the block copolymer design not only conduces to forming a self‐assembled microphase separation to stabilize the trapped charge in the polymer electret, but also triggers multiband photoresponding of the photonic FET memory. [ABSTRACT FROM AUTHOR]

A key challenge in the realization of circularly polarized polymer light‐emitting diodes (CP‐PLEDs) is the generation of highly circularly polarized deep‐blue electroluminescence (EL). Here, by blending the achiral luminescent polymer poly(9,9‐dioctylfluorene) (PFO) with a helically chiral molecule 1‐aza[6]helicene the authors present CP‐PLEDs with state‐of‐the‐art device performance for deep‐blue CP emission: for an inverted device with a semicrystalline microstructure a current efficiency (CE) of 1.13 cd A−1, a power efficiency (PE) of 0.81 lm W−1, and an EL dissymmetry (gEL) of −0.42 are achieved; for the planarized and extended "β‐phase" chain conformation a CE of 1.23 cd A−1, a PE of 0.63 lm W−1, and a gEL of −0.44 are achieved. While these two phases achieve both high CE, as well as gEL, the latter affords the first demonstration of chiral β‐phase emission from solid‐state PFO devices. Such strongly circularly polarized light is generated from a supramolecular assembly of interacting planar polymer backbones. The authors rationalize that the strong chiroptical effects observed within such chiral β‐phase PFO domains originate from coupled interchain aggregates. The findings not only demonstrate efficient deep‐blue CP‐PLEDs, but also provide insight into the mechanisms that underpin the strong CP emission from excitonically coupled polymer chains. [ABSTRACT FROM AUTHOR]

It is well known that macromolecular structure, including composition, topology and sequence, significantly determines the properties of conjugated polymers/oligomers. To accurately understand the structure‐induced properties, discrete oligomers/polymers with molecularly defined structures are the ideal model because they provide distinct nonstatistical results. Herein, a series of discrete conjugated fluorene‐azo oligomers with different positions of the azobenzene units along the main chain (i.e., sequence) are efficiently prepared based on CuAAC "click" chemistry via a stepwise chain‐growth strategy. Position‐dependent behavior has an evident impact on the properties of oligomers, such as thermal properties, optical properties and photoresponsive behavior in both solution and thin film states. In addition, the fluorene‐azo oligomers show less photodegradation of 9,9‐dioctyl‐fluorene in the solid‐state than oligofluorene during UV light irradiation; however, position‐dependent photodegradation is found in solution. Optimized configurations and UV–vis absorption spectra of fluorene‐azo oligomers are calculated by density functional theory. Experimental results and theoretical analysis indicate that the location of azobenzene can play a dominant role in determining the properties of fluorene‐azo oligomers resulting from sequence‐mandated conformational changes. Undoubtedly, this work can provide deeper insight into the structure–property relationships based on precisely sequence‐defined polymer structures. [ABSTRACT FROM AUTHOR]

[Display omitted] • Conjugated polyelectrolytes with FRET pairs act as proximity sensors in an assembly. • Polycationic spermine can be detected via binding-induced fluorescence quenching. • Bulky tryptamine dissociates charge-driven complexes by creating steric hindrance. • Charge-driven complexes serve as a platform for small analyte detection via FRET. We developed sensing platforms to detect and differentiate various types of biogenic amines, cadaverine, putrescine, spermine, histamine, tyramine and tryptamine by monitoring the changes in fluorescence signal. The sensing platforms comprised a carboxylated polyfluorene derivative doped with benzothiadiazole acceptor moieties in a small fraction (20%). When utilized as an individual sensing component, the conjugated polyelectrolyte detects all BAs nonselectively via binding-induced fluorescence quenching. If the conjugated polyelectrolyte forms an intermediary charge-driven complex with an oppositely charged surfactant, a Förster resonance energy transfer (FRET) response is triggered. Biogenic amines are detected through their effects on the FRET signal as enhancement, reduction, or no effect. We formed intermediary charge-driven complexes at nonstoichiometric, cation deficient and excess conditions. Supramolecular interactions governed the co-assembly and disassembly caused by the targeted amines on the conjugated polyelectrolyte-surfactant complex. Therefore, structural and charge-related differences enabled their selective detection in our sensing platforms. Among them, spermine exhibited the highest FRET enhancement effect due to its polycationic aliphatic structure by engaging in multi-point interchain contacts among conjugated polyelectrolyte chains. In contrast, tryptamine showed a unique quenching effect on the FRET signal due to the steric hindrance created by its bulky, heterocyclic structure, leading to the dissociation of the complexes. [ABSTRACT FROM AUTHOR]

Photonic transistor memory, which adopts the structure of a field-effect transistor, combines optical and electronic principles. Conjugated block copolymers (BCPs) are promising electret materials for optoelectronic applications. In this study, a series of BCPs comprising poly[2,7-(9,9-dioctylfluorene)] (PFO: A block) and poly(n -butyl acrylate- random -2-ureido-4[1H]pyrimidinone acrylate) (n BA- r -UPyA: B block), with linear-diblock (AB), branched (AB 2), and linear-triblock (BAB) architectures, are synthesized to investigate hydrogen bonding effect stemming from UPyA groups. After thermal annealing, the soft segments of BCPs lead to self-assembled arrangements and smoother morphologies, providing an excellent interface for the deposition of the semiconducting channel layer. Furthermore, forming vertical phase-separated structures through thermal annealing significantly enhances the electron-capture capability. Subsequently, the BCP materials are applied in photonic transistor memory and conducted with electrical characterization. Our study reveals that different compositions of BCP architectures have a corresponding impact on the performance of photonic transistor memory devices. Consequently, AB of PFO- b -P(n BA- r -UPyA)s with a linear-diblock architecture presents an outperforming memory ratio of ∼105, outstanding memory stability over 104 s, and durability to consecutive write/erase processes. [Display omitted] • Architectural optimization of conjugated block copolymers. • Polyfluorene-based block copolymers with hydrogen-bonded coils. • Self-assembled arrangements of vertical phase separations. • Photonic transistor memory with a high memory ratio of 105. • Outstanding memory stability over 104 s and durability to consecutive write/erase cycles. [ABSTRACT FROM AUTHOR]

In this study, we successfully fabricated an intrinsically stretchable light‐emitting diode (LED) by using a new conjugated rod–coil block copolymer, poly[2,7‐(9,9‐dioctylfluorene)]‐block‐poly(isoprene) (PF‐b‐PI). (PF conjugated rods and PI coils exhibited fluorescent and intrinsically stretchable properties, respectively. Copolymers with three different rod/coil ratios, namely PF18K‐b‐PI5K, PF12K‐b‐PI5K and PF12K‐b‐PI10K, were utilized for elastic LED demonstration. Notably, PF18K‐b‐PI5K and PF12K‐b‐PI5K LEDs can work under a strain of 140% because of suitable ratios of rod/coil lengths. Finally, a stretchable PF12K‐b‐PI5K LED was measured with a low voltage of 2 V and with a brightness of 70 cd m−2 at 10 V. This LED was subjected to 100 cycles of luminance–strain testing under 50% strain and it maintained a stable level of brightness. These results demonstrated that the luminescent PF12K‐b‐PI5K rod–coil block copolymers exhibit exceptional stretchability and high stability; these copolymers can be used in stretchable LEDs for a wide range of applications. © 2020 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Aromatic high-performance triphenylamine-based polyfluorenes (PTPAFs) have been successfully constructed by palladium-catalyzed polycondensation reaction. The chemical structures of the resulting PTPAFs are confirmed by means of Fourier-transform infrared spectroscopy and nuclear magnetic resonance, and the testing results showed a good agreement with the proposed structures. The resulted polymers show excellent solubility, high thermal stability with the decomposition temperatures (Td5%) over 320 °C and the glass transition temperatures (Tg) over 305 °C. The PTPAF1 and the PTPAF2 exhibit the enhanced high occupied molecular orbital (HOMO) energy levels (− 3.93 eV, − 4.00 eV, respectively) and the depressed low unoccupied molecular orbital (LUMO) energy levels (− 0.99 eV, − 1.41 eV, respectively). Owing to their special structures, PTPAFs showed encouraging photonic luminescence and good electroactivity and could be used as a potential light source in the blue region. [ABSTRACT FROM AUTHOR]

Simultaneous enhancement of photoluminescence quantum efficiency (PLQE) and optical gain in semiconducting polymer films is desirable for optically‐ or electrically‐pumped organic solid‐state lasers. In this work, a simple self‐dilution effect is achieved by introducing a small amount (≈10% by weight) of 2,5‐dimethyl‐1,4‐phenylene (DP) units in the backbone of poly(9,9‐dioctylfluorene) (PFO). The resulting copolymers, compared with PFO (PLQE 39%), exhibit a significantly increased PLQE (66%) while keeping similar absorption and photoluminescence profile, concomitant with an enhancement in optical gain properties. The radiative decay rate increases sharply along with a sustaining reduction in the non‐radiative decay rate in these copolymers, following similar principle of physical dilution of a luminescent compound in solution or in a polymer matrix. Among all the copolymers, the one containing 10% DP units exhibits the lowest amplified spontaneous emission/distributed feedback laser threshold (10.9 nJ/1.4 nJ, eightfold reduction), and the highest gain coefficient (54.4 cm−1). The results demonstrate that a moderate DP/fluorene ratio can maximize the beneficial self‐dilution effects. These investigations shed light on new design strategies to achieve conjugated polymers with concurrent high PLQE and large optical gain properties. [ABSTRACT FROM AUTHOR]

After a fluorene‐based anion exchange membrane (AEM) containing 1‐isopropyl‐2‐methylimidazolium with alkyl side chains was prepared, the membrane properties, including OH– conductivities, ion exchange capacity (IEC), water uptake, swelling ratio, and chemical and thermal stabilities of the obtained membrane were assessed. The synthesized membrane exhibited low water uptake and good dimensional stability with adequate hydroxide conductivity. For example, the AEM showed a swelling ratio of 7% and hydroxide conductivity of 46 mS cm−1 at 80 °C in liquid water. The chemical stability was investigated in 1 M NaOH solution at room temperature and at 80 °C. At both temperatures, degradation of the imidazolium cationic groups was observed, although the main chain was chemically stable. All results obtained from this research are expected to provide important direction and insight for AEM synthesis for practical applications in anion exchange membrane fuel cells. [ABSTRACT FROM AUTHOR]

We investigated the synthesis of polyfluorene with a pinacol boronate (PinB) moiety at one end and with controlled molecular weight by means of Suzuki–Miyaura coupling polymerization of pinacol (7‐bromo‐9,9‐dioctyl‐9H‐fluoren‐2‐yl)boronate (1) with a palladium(0) precatalyst in the presence of pinacol 4‐trifluoromethylphenylboronate (2) as a chain terminator and CsF/18‐crown‐6 as a base. When we used AmPhos Pd G2, which has a propensity for intramolecular catalyst transfer on a π‐electron face, polyfluorene with the PinB moiety at one end and PhCF3 (derived from 2) at the other end was obtained, and the molecular weight increased in proportion to the feed ratio of [1]0/[catalyst]0, though the molecular weight distribution was broad. Since the molecular weight also linearly increased with respect to the conversion of 1 until the middle stage of polymerization, the polymerization appears to involve chain‐growth polymerization through intramolecular catalyst transfer from the Pd catalyst inserted into the CBr bond of 1. The broad molecular weight distribution might be mainly due to slow initiation and slow termination with 2, rather than polymer–polymer coupling. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 2498–2504 [ABSTRACT FROM AUTHOR]

Pendant carboxyl groups were introduced into donor–acceptor polyfluorene carrying benzothiadiazole as an acceptor moiety. The emission color from its solution was different depending on the solvent. While the methanol solution of the polymer exhibited blue emission, yellow emission was observed from its tetrahydrofuran solution. Influence of solvent polarity, solution concentration, temperature, and addition of acid on photoluminescence properties indicated that the observed change in emission color was due to polymer aggregation coming from inter and/or intramolecular interaction between pendant carboxyl groups. Polyfluorene carrying benzothiadiazole moiety with pendant amino groups also exhibited emission color change and was useful as a fluorimetric sensor for polyacid. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel graphene quantum dots-polyfluorene (GQD@PF) hybrid was synthesized. • GQD@PF was used to modify pencil graphite electrode (PGE) surface. • Modified electrode was used as a DNA biosensor to test MC-dsDNA interactions. • 24 fold enhance in electroactive surface area was achieved with GQD@PF modification. • GQD@PF-PGE allows an approximately 56 times more sensitive DNA analysis. A novel graphene quantum dots (GQD) / polyfluorene (PF) nanocomposite was deposited on the disposable pencil tip graphite electrode (PGE) and proven to be an efficient nanosensor for analysis of the electrochemical interaction between the antitumor compound mitomycin C (MC) with double stranded DNA (ds-DNA). This modified electrode (GQD@PF-PGE) was prepared in four steps: hydrothermal, chemical oxidation, ultrasonication and electro-oxidation processes. GQD, PF, GQD@PF and GQD@PF-PGE have been characterized by different analytical techniques such as SEM, TEM, XRD, FTIR, UV–Vis, EIS. Compared to bare PGE, GQD@PF modified PGE performed approximately 56 times more sensitive analysis when evaluating the guanine oxidation signals measured by DPV. CV and EIS measurements also showed that GQD@PF-PGE possesses a fast electron transfer as compared to bare electrode and exhibit a remarkable electrocatalytic activity towards both guanine and MC electrooxidation. Comprehensive optimization studies have also been carried out for the developed new nanobiosensor. [ABSTRACT FROM AUTHOR]

Fluorene-containing poly(aryl ether nitrile) (FPAN) was prepared by a typically aromatic nucleophilic substitution polymerization. The chemical structure of FPAN was confirmed by FTIR and 1H NMR spectroscopy. Different morphologies of FPAN fibers could obtain through electrospinning. The light-emission properties of polymer in solution, casting film and fibrous membrane were examined by spectrofluorometry. This polymer had good thermal properties with glass-transition temperatures at 280 °C and 10 % weight loss temperatures in the range of 497–502 °C. Additionally, the contact angles in the thin-film state and electrospun fiber membranes were examined. The water contact angle of fiber membrane was improved compared to that of casting film which could reach to the 137 °. The resulting material exhibited stable luminescent intensity, possessed considerable thermal stability, and could be facilely processed into device for optical field applications. [ABSTRACT FROM AUTHOR]

• Preparation of cationic polyfluorene based fluorescent nanoparticle (CPF). • pH dependent reversible "turn off/turn on" emission of CPF with folic acid (FA). • CPF is highly sensitive to FA at biological pH of 7.4 to turn off 91% fluorescence. • FA pre-treated folate receptor positive cancer cell imaging by CPF nanoprobe. 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. [ABSTRACT FROM AUTHOR]

• NBR as a matrix is efficient to protect conjugated polymer. • The blends support 7 h of UV-light exposure. • The degradation showed the formation alcohols and/or peroxides. • Blends of conjugated and non-conjugated polymer were prepared by spin coating technique. 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. [ABSTRACT FROM AUTHOR]

We report on solution aggregates and backbone conformation of poly(9‐undecyl‐9‐methyl‐fluorene) (PF1‐11) and poly(9‐pentadecyl‐9‐methyl‐fluorene) (PF1‐15), having two different side chains compared with poly(9,9‐dihexylfluorene) (PF6) and poly(9,9‐dioctylfluorene) (PF8) with two identical side chains. In the poor solvent methylcyclohexane (MCH), X‐ray scattering indicates that PF1‐11 and PF1‐15 appear as three‐dimensional aggregates (5–10 nm wide and thick), forming ribbon‐like agglomerates (correlation lengths of 100 nm). PF6 and PF8 appear as two‐dimensional aggregates (>10 nm wide and 2–3 nm thick) involving ribbon‐like agglomerates (correlation lengths much greater than 100 nm). Upon heating, all aggregates undergo a gel–sol transition which occurs at lower temperatures for PF1‐11 and PF1‐15 (<60°C) than for PF6 and PF8 (>80°C). In the good solvent toluene, PF1‐11 and PF1‐15 form networks of cylindrical particles. The mesh size and the cylinder radius are smaller in 24°C toluene (60 nm, 0.5 nm) than in 60°C MCH (300 nm, 1–2 nm). Nuclear magnetic resonance spectra in toluene‐d8 together with density functional theory calculations suggest higher torsion angles between polymer repeat units for PF6, PF8, and PF1‐11 (less planar conformation) and a gauche arrangement of the dihedral angles between the bridge carbon atom and the side chain methylene groups in PF1‐15. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 826–837 [ABSTRACT FROM AUTHOR]

Polyfluorenes bearing imidazole and triphenylamine moieties in the main chain were synthesized. The imidazole/triphenylamine molar ratios in the polymer backbone were 100/0 (PFIM100), 50/50 (PFIM50) and 25/75 (PFIM25). Cyclic voltammetry revealed reversible oxidation only for polymers containing triphenylamine moieties (PFIM50 and PFIM25) and irreversible reduction for all polymers. Optical properties of the polymers were investigated using UV‐visible and photoluminescence spectroscopies in solution. The sensing properties of PFIM100 were investigated. The polymer showed recognition towards two analytes, Fe2+ and Hg2+. PFIM100 exhibited selective fluorescence 'turn‐off' response to Fe2+ cations. Interaction of PFIM100 with I− anions produced a non‐emissive complex. The PFIM100/I− complex exhibited excellent 'turn‐on' sensing properties for detection of Hg2+. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Emulsion-based, resonant infrared matrix-assisted pulsed laser evaporation (RIR-MAPLE) was used to deposit thin films of polyfluorene (PFO) with semi-crystalline phase domains (β-PFO), which has been performed, previously, only by solution phase processing. Various target emulsion recipes were studied, with emphasis on the primary solvent choice, emulsion mixing time, secondary solvent concentration, or total water concentration. The emulsified particle size for each recipe was compared using dynamic light scattering. Additionally, elevated growth temperature of the substrate was considered for controlling film formation. The surface quality of films was determined by atomic force microscopy, and β-PFO concentration was monitored using photoluminescence or UV–visible absorbance spectroscopy. Importantly, in contrast to solution-based deposition of β-PFO in thin films, emulsion-based RIR-MAPLE demonstrated the ability to increase β-PFO content without degrading, simultaneously, the surface properties of the films. This initial result helps establish the ability of RIR-MAPLE to control and promote semi-crystalline phases in polymer films. [ABSTRACT FROM AUTHOR]

We report on X‐ray scattering measurements of helical poly[9,9‐bis(2‐ethylhexyl)‐fluorene‐2,7‐diyl] by mapping the sample with 10 μm spatial resolution from 0.3 GPa to 36 GPa. We follow the strongest 00l reflection, which moves toward higher scattering angles with pressure indicating planarization of helical polyfluorene. Lateral inhomogeneity is increased for >10 GPa concomitant with the solidification of the pressure transmitting medium (a 4:1 mixture of methanol and ethanol). We also follow the 00l reflection with increasing temperature at the constant pressure of 4.3 GPa in neon. We observe a sharp shift toward higher scattering angles indicative of a phase transition at 167–176 °C. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 392–396 X‐ray scattering data from polyfluorene polymer is collected by mapping the sample with 10 μm spatial resolution from 0.3 GPa to 36 GPa. The structural inhomogeneity is characterized. The data are also collected with increasing temperature at 4.3 GPa. A phase transtion is identified at about 170°C. [ABSTRACT FROM AUTHOR]

We studied the effects of postannealing on the performance of polyfluorene organic light-emitting diodes (OLEDs) with a pure poly(9, $9'$ -dioctylfluorene-co-benzothiadiazole) (F8BT) emissive layer. After annealing at 150 °C–200 °C, the OLED exhibited the lowest voltage and highest luminance. This correlated well with the highest crystallinity of the F8BT film, as revealed by X-ray diffraction. As the temperature was raised up to 300 °C, the voltage at 50 mA/cm2 increased by 2.7 V, and the luminance decreased by 44%, whereas the device lifetime was markedly extended by as much as 13 times. The loss of crystallinity at high temperatures suggested that structural disorders were created, resulting in degraded charge transport and radiative process. Our study demonstrates the necessity of posttreatment above the glass transition temperature to obtain desirable efficiency and lifetime of solution-processed polyfluorene OLEDs. [ABSTRACT FROM AUTHOR]

An organic compound (1'-4-iodophenyl) trihidroxysilane (OHIPhSi) functionalized as hole transporting material was synthesized and used as interface self-assembled monolayers (SAM) on ITO film. To analyze the effect of a SAM layers on the characteristics an organic light emitting diode (Organic LED), a typical Organic LED device (ITO/OHIPhSi/polymer/LiF/Al) was fabricated. The SAM-treatment ITO device performed a higher mobility than the bare ITO device. The carrier mobility properties were calculated by space-charge-limited current measurements (SCLC) technique for polyfluorene (PFO) polymer Organic LED devices. [ABSTRACT FROM AUTHOR]

Results of studying the optical and electrical characteristics of single- and two-layer polymer OLED structures with different thicknesses of radiating layers are presented. It is shown that the efficiency of the OLED structures with thick layers reaches 6.9 cd/A, while similar thin-layer structures have the efficiency 10 times smaller. An increase in the thickness of the radiating layer of the polymer as well as incorporation of additional electron transport layer leads to a decrease in the leakage current and an increase in the efficiency; however, it changes the electroluminescence spectrum of the device. [ABSTRACT FROM AUTHOR]