The Experts below are selected from a list of 7245 Experts worldwide ranked by ideXlab platform
Fosong Wang - One of the best experts on this subject based on the ideXlab platform.
-
white electroluminescence from star like single polymer systems 2 1 3 benzothiadiazole derivatives dopant as orange cores and Polyfluorene host as six blue arms
Advanced Materials, 2011Co-Authors: Lei Chen, Lixiang Wang, Xiabin Jing, Yanxiang Cheng, Zhiyuan Xie, Fosong WangAbstract:By incorporating six blue emissive Polyfluorene arms into star-shaped orange emissive cores, two kinds of star-like white electroluminescent single-polymer systems are designed and synthesized. Energy transfer from the Polyfluorene arms to the orange emissive cores is observed and a concentration quenching effect is effectively suppressed. Through thermal annealing, a highly efficient white emissive single-layer device is achieved with CIE coordinates of (0.33, 0.35) and a current efficiency of 18.01 cd A(-1).
-
white electroluminescence from a single polymer system with simultaneous two color emission Polyfluorene as the blue host and a 2 1 3 benzothiadiazole derivative as the orange dopant
Advanced Functional Materials, 2006Co-Authors: Junkai Liu, Lixiang Wang, Quanguo Zhou, Yanhou Geng, Xiabin Jing, Y X Cheng, Fosong WangAbstract:New single-polymer electroluminescent systems containing two individual emission species—Polyfluorenes as a blue host and 2,1,3-benzothiadiazole derivative units as an orange dopant on the main chain—have been designed and synthesized. The resulting single polymers are found to have highly efficient white electroluminescence with simultaneous blue (λmax = 421 nm/445 nm) and orange emission (λmax = 564 nm) from the corresponding emitting species. The influence of the photoluminescence (PL) efficiencies of both the blue and orange species on the electroluminescence (EL) efficiencies of white polymer light-emitting diodes (PLEDs) based on the single-polymer systems has been investigated. The introduction of the highly efficient 4,7-bis(4-(N-phenyl-N-(4-methylphenyl)amino)phenyl)-2,1,3-benzothiadiazole unit to the main chain of Polyfluorene provides significant improvement in EL efficiency. For a single-layer device fabricated in air (indium tin oxide/poly(3,4-ethylenedioxythiophene): poly(styrene sulfonic acid/polymer/Ca/Al), pure-white electroluminescence with Commission Internationale de l'Eclairage (CIE) coordinates of (0.35,0.32), maximum brightness of 12 300 cd m–2, luminance efficiency of 7.30 cd A–1, and power efficiency of 3.34 lm W–1 can be obtained. This device is approximately two times more efficient than that utilizing a single Polyfluorene containing 1,8-naphthalimide moieties, and shows remarkable improvement over the corresponding blend systems in terms of efficiency and color stability. Thermal treatment of the single-layer device before cathode deposition leads to the further improvement of the device performance, with CIE coordinates of (0.35,0.34), turn-on voltage of 3.5 V, luminance efficiency of 8.99 cd A–1, power efficiency of 5.75 lm W–1, external quantum efficiency of 3.8 %, and maximum brightness of 12 680 cd m–2. This performance is roughly comparable to that of white organic light-emitting diodes (WOLEDs) with multilayer device structures and complicated fabrication processes.
-
Synthesis and properties of Polyfluorenes containing 1,8-naphthalimide moieties for white electroluminescence
Synthetic Metals, 2005Co-Authors: Quanguo Zhou, Lixiang Wang, Yangxiang Cheng, Yanhou Geng, Xiabin Jing, Fosong WangAbstract:Abstract Two Polyfluorenes containing 1,8-Naphthalimide units were synthesized by Yamamoto polycondensation reaction. The 1,8-naphthalimide moieties act as both electron and hole trap in the resulting polymers, leading to the EL spectra different from the PL spectra in film. White electroluminescence with a maximum brightness of 11100 cd/m 2 , an external quantum efficiency of 2.0% and CIE coordinates of (0.26, 0.36) has been realized through partial energy transfer from Polyfluorene to 1,8-naphthalimide moieties.
-
Polyfluorenes containing 1.8-naphthalimide dye as endcapping groups
Synthetic Metals, 2005Co-Authors: Jianxin Cao, Lixiang Wang, Quanguo Zhou, Yanhou Geng, Xiabin Jing, Yanxiang Cheng, Fosong WangAbstract:Abstract A series of Polyfluorene derivatives endcapped by 0.1–2 mol% 1,8-naphthalimide dye were synthesized by Yamamoto coupling reaction. The resulting polymers show the promising electroluminescence (EL) performance with emission predominantly from the 1,8-naphthalimide unit due to energy transfer and charge trapping from Polyfluorene backbone to 1,8-naphthalimide dye. Single-layer devices were fabricated with a device configuration of ITO/PEDOT/polymer/Ca/Al. Among all the devices tested, the device of NFP50 exhibited the current efficiency of 7.40 cd/A, the power efficiency of 2.89 lm/W and the maximum brightness of 19280 cd/m 2 , about 30 times more efficient than that of Polyfluorene without endcapping groups.
Wei Huang - One of the best experts on this subject based on the ideXlab platform.
-
energy transfer in Polyfluorene copolymer used for white light organic light emitting device
Organic Electronics, 2013Co-Authors: Hua Wang, Taiju Tsuboi, Zhuxia Zhang, Yanqin Miao, Yuying Hao, Xuguang Liu, Wei HuangAbstract:Abstract Luminescence properties of a type of Polyfluorene copolymer (PFO–DBT5) used for white-light organic light emitting device (OLED) were studied and discussed, in which a very low concentration of 0.05 mol% 4,7-bithienyl-2,1,3-benzothiadiazole (DBT) molecules were inserted in Polyfluorene chain as orange-light unit. From the spectroscopic analysis of PFO–DBT5 in solution and nanoparticles, it is concluded that inter-chain Forster energy transfer from Polyfluorene segments to DBT units play major role in process of white-light emission of PFO–DBT5. By measurement of electroluminescent properties, it is found that annealing of PFO–DBT5 film in vacuum is favorable for improving white-light emission owing to enhancement in inter-chain Forster energy transfer. CIE coordinates (0.38, 0.33) were obtained under the annealing temperature of 140 °C. It was found that the annealing temperature affects the luminance and efficiency of white-light OLED. The optimum annealing temperature was 100 °C.
-
conjugated polymers with cationic iridium iii complexes in the side chain for flash memory devices utilizing switchable through space charge transfer
Journal of Materials Chemistry, 2012Co-Authors: Mingdong Yi, Qiang Zhao, Wenjuan Xu, Chao Tang, Shanghui Ye, Wei HuangAbstract:Polycarbazole and Polyfluorene containing cationic iridium(III) complexes in the side-chain have been designed and synthesized. Both polymers have been demonstrated to show conductance switching behavior and non-volatile flash memory devices based on them were successfully realized, in which the formation and dissociation of through-space charge-transfer states from the conjugated polymer “sea” to the Ir(III) complex “island”, controlled by voltage, are responsible for the conductance switching behavior and memory effect. The devices exhibit low reading, writing, and erasing voltages and a high ON/OFF current ratio. Both ON and OFF states are stable up to 107 read cycles at a read voltage of −1.0 V. Due to the different chemical structures of the polymer main-chain, the two devices show different threshold voltages. The polycarbazole derivative exhibits higher HOMO and LUMO levels compared with the Polyfluorene analogue. Thus, the threshold voltage from the OFF to ON state of the device based on the polycarbazole derivative is obviously lower than that of the Polyfluorene derivative-based device because of the low energy barrier between the work function of the ITO anode and the HOMO level of the polycarbazole derivative. Similarly, the threshold voltage from the ON to OFF state is evidently higher because the energy barrier of electron injection from Al into the LUMO of the polycarbazole derivative is slightly higher than that of the Polyfluorene analogue. Thus, the threshold voltages of memory devices may be rationally modulated by modifying the chemical structure of polymers.
-
Polyfluorene‐Based Blue‐Emitting Materials
Macromolecular Chemistry and Physics, 2009Co-Authors: Qiang Zhao, Shujuan Liu, Wei HuangAbstract:Polyfluorenes are a class of promising blue light-emitting conjugated polymer due to their excellent optoelectronic properties. However, the applications of Polyfluorenes in polymer light-emitting diodes (PLEDs) have been hampered by the appearance of long-wavelength green emission, leading to the problem of color purity and stability. Hence, the preparation of pure blue-emitting Polyfluorenes becomes very important for the realization of real blue-emitting PLEDs. In this short review, we introduce the efforts made by our group to realize Polyfluorenes with pure blue emission, including the incorporation of spirobifluorene units, hetero-fluorene units, hyperbranched, and star-shaped structures into polymer backbones.
-
Novel blue light-emitting hyperbranched Polyfluorenes incorporating carbazole kinked structure
European Polymer Journal, 2008Co-Authors: Wen-yong Lai, Daoyong Chen, Wei HuangAbstract:Abstract A novel series of soluble hyperbranched Polyfluorenes P1 − P6 with various branching degrees and contents of kinked carbazole units were successfully synthesized with good yields and high molecular weight via a facile “A2 + B2 + C3 + D2” approach. The thermal, optical, and electrochemical properties as well as thermal spectral stability of the resulting hypberbranched polymers were investigated. All polymers exhibited good thermal stabilities and bright blue emission in both solutions and solid-states. Hyperbranched Polyfluorenes ( P3 and P6 ) exhibited improved spectral stability upon annealing at 200 °C in air, in sharp contrast to the linear poly(9,9-dihexylfluorene) ( PDHF ) that showed significant additional green emission at ca. 530 nm within minutes. In particular, outstanding spectral stability was observed with carbazole-incorporating hyperbranched Polyfluorene P6 . Electrochemical characterization indicated that the presence of carbazole also effectively raised the HOMO level with respect to that of Polyfluorene homopolymer, suggesting better hole-injection properties. Hence, the incorporation of kinked carbazole unit into hyperbranched Polyfluorenes could provide a new methodology for preparing blue light-emitting polymers with improved optoelectronic characteristics.
-
Blue-light-emitting hyperbranched Polyfluorenes with photocrosslinkable group
Journal of Optoelectronics and Advanced Materials, 2007Co-Authors: Duo-feng Tang, Lianhui Wang, Guian Wen, Wei Wei, Yu Xin, Xing-rong Zhu, Wei HuangAbstract:The blue-light-emitting crosslinkable hyperbranched Polyfluorene P2 with higher content of branched unit were synthesized by the palladium-catalyzed Suzuki coupling reaction. The molecular weight and thermal behavior was analysized by GPC, DSC and TG By contrast with the lower branched unit content hyperbranched Polyfluorene P1 and linear Polyfluorene PO, the photoluminescence (PL) spectra of P2 shows excellent stability even annealing in air at 200 °C after 3 hours after crosslink. The stabilized hyperbranched Polyfluorene can be used in multilayer and multicolor PLED.
Lixiang Wang - One of the best experts on this subject based on the ideXlab platform.
-
white electroluminescence from star like single polymer systems 2 1 3 benzothiadiazole derivatives dopant as orange cores and Polyfluorene host as six blue arms
Advanced Materials, 2011Co-Authors: Lei Chen, Lixiang Wang, Xiabin Jing, Yanxiang Cheng, Zhiyuan Xie, Fosong WangAbstract:By incorporating six blue emissive Polyfluorene arms into star-shaped orange emissive cores, two kinds of star-like white electroluminescent single-polymer systems are designed and synthesized. Energy transfer from the Polyfluorene arms to the orange emissive cores is observed and a concentration quenching effect is effectively suppressed. Through thermal annealing, a highly efficient white emissive single-layer device is achieved with CIE coordinates of (0.33, 0.35) and a current efficiency of 18.01 cd A(-1).
-
phosphonate functionalized Polyfluorene film sensors for sensitive detection of iron iii in both organic and aqueous media
Macromolecules, 2010Co-Authors: Hui Tong, Lixiang WangAbstract:A novel conjugated polymer (CP) based thin film sensor toward Fe3+ was prepared by covalent immobilization of a phosphonate-functionalized Polyfluorene on glass surface. Contact angle, XPS and steady-state fluorescence measurements proved that the Polyfluorene was successfully chemically conjugated on the substrate surface. Like the organic solution and spin-casting film of this Polyfluorene, the fluorescence of the immobilized film can be selectively quenched by Fe3+ in both organic and aqueous solutions. Limit of detection of this film sensor for Fe3+ could be down to 8.4 ppb in THF solution and 0.14 ppm in aqueous solution, which were among the best results for Fe3+ sensing by fluorescence film sensors reported so far. Compared with the fluorescence quenching properties of the same Polyfluorene in THF solution and in spin-casting film, both quenching constant and detection limit of the immobilized film were improved by 1 order of magnitude, which demonstrated the advantage of the immobilized film fluor...
-
white electroluminescence from a single polymer system with simultaneous two color emission Polyfluorene as the blue host and a 2 1 3 benzothiadiazole derivative as the orange dopant
Advanced Functional Materials, 2006Co-Authors: Junkai Liu, Lixiang Wang, Quanguo Zhou, Yanhou Geng, Xiabin Jing, Y X Cheng, Fosong WangAbstract:New single-polymer electroluminescent systems containing two individual emission species—Polyfluorenes as a blue host and 2,1,3-benzothiadiazole derivative units as an orange dopant on the main chain—have been designed and synthesized. The resulting single polymers are found to have highly efficient white electroluminescence with simultaneous blue (λmax = 421 nm/445 nm) and orange emission (λmax = 564 nm) from the corresponding emitting species. The influence of the photoluminescence (PL) efficiencies of both the blue and orange species on the electroluminescence (EL) efficiencies of white polymer light-emitting diodes (PLEDs) based on the single-polymer systems has been investigated. The introduction of the highly efficient 4,7-bis(4-(N-phenyl-N-(4-methylphenyl)amino)phenyl)-2,1,3-benzothiadiazole unit to the main chain of Polyfluorene provides significant improvement in EL efficiency. For a single-layer device fabricated in air (indium tin oxide/poly(3,4-ethylenedioxythiophene): poly(styrene sulfonic acid/polymer/Ca/Al), pure-white electroluminescence with Commission Internationale de l'Eclairage (CIE) coordinates of (0.35,0.32), maximum brightness of 12 300 cd m–2, luminance efficiency of 7.30 cd A–1, and power efficiency of 3.34 lm W–1 can be obtained. This device is approximately two times more efficient than that utilizing a single Polyfluorene containing 1,8-naphthalimide moieties, and shows remarkable improvement over the corresponding blend systems in terms of efficiency and color stability. Thermal treatment of the single-layer device before cathode deposition leads to the further improvement of the device performance, with CIE coordinates of (0.35,0.34), turn-on voltage of 3.5 V, luminance efficiency of 8.99 cd A–1, power efficiency of 5.75 lm W–1, external quantum efficiency of 3.8 %, and maximum brightness of 12 680 cd m–2. This performance is roughly comparable to that of white organic light-emitting diodes (WOLEDs) with multilayer device structures and complicated fabrication processes.
-
Synthesis and properties of Polyfluorenes containing 1,8-naphthalimide moieties for white electroluminescence
Synthetic Metals, 2005Co-Authors: Quanguo Zhou, Lixiang Wang, Yangxiang Cheng, Yanhou Geng, Xiabin Jing, Fosong WangAbstract:Abstract Two Polyfluorenes containing 1,8-Naphthalimide units were synthesized by Yamamoto polycondensation reaction. The 1,8-naphthalimide moieties act as both electron and hole trap in the resulting polymers, leading to the EL spectra different from the PL spectra in film. White electroluminescence with a maximum brightness of 11100 cd/m 2 , an external quantum efficiency of 2.0% and CIE coordinates of (0.26, 0.36) has been realized through partial energy transfer from Polyfluorene to 1,8-naphthalimide moieties.
-
Polyfluorenes containing 1.8-naphthalimide dye as endcapping groups
Synthetic Metals, 2005Co-Authors: Jianxin Cao, Lixiang Wang, Quanguo Zhou, Yanhou Geng, Xiabin Jing, Yanxiang Cheng, Fosong WangAbstract:Abstract A series of Polyfluorene derivatives endcapped by 0.1–2 mol% 1,8-naphthalimide dye were synthesized by Yamamoto coupling reaction. The resulting polymers show the promising electroluminescence (EL) performance with emission predominantly from the 1,8-naphthalimide unit due to energy transfer and charge trapping from Polyfluorene backbone to 1,8-naphthalimide dye. Single-layer devices were fabricated with a device configuration of ITO/PEDOT/polymer/Ca/Al. Among all the devices tested, the device of NFP50 exhibited the current efficiency of 7.40 cd/A, the power efficiency of 2.89 lm/W and the maximum brightness of 19280 cd/m 2 , about 30 times more efficient than that of Polyfluorene without endcapping groups.
Ullrich Scherf - One of the best experts on this subject based on the ideXlab platform.
-
Enhanced charge-carrier mobility in β -phase Polyfluorene
Physical Review B, 2006Co-Authors: Paulette Prins, Ullrich Scherf, Ferdinand C. Grozema, Benjamin S. Nehls, Tony Farrell, Laurens D. A. SiebbelesAbstract:Alkyl substituted Polyfluorenes are promising candidates for use in organic display applications due to efficient, pure blue (polarized) luminescence, high charge carrier mobility, and good processabilty. Poly(9,9?-dioctylfluorene) (PFO) is an especially interesting Polyfluorene derivative, because of its self-organization into distinct supramolecular structures at room temperature. In addition to the amorphous glassy phase, PFO exhibits a unique packing behavior, the so-called ?-phase formation, which leads to a higher degree of organization. We show that the ?-phase is an energetically favorable environment for charge carriers. We look into the migration of charges from glassy Polyfluorene to areas where PFO exhibits ?-phase organization and find that the charge carrier mobility is higher in ?-phase Polyfluorene than in glassy Polyfluorene. Our results illustrate that the order on a supramolecular scale determines the conductive properties of conjugated polymers to a large extent. We conclude that the performance of devices based on Polyfluorene can be significantly improved by the enhancement of the supramolecular order.
-
on chain fluorenone defect emission from single Polyfluorene molecules in the absence of intermolecular interactions
Advanced Functional Materials, 2006Co-Authors: K D Becker, John M. Lupton, Benjamin S. Nehls, Jochen Feldmann, Frank Galbrecht, Deqing Gao, Ullrich ScherfAbstract:The emission of semiconducting Polyfluorenes is often accompanied by an undesired feature in the green spectral region. Whereas a number of previous investigations have argued in favor of a monomolecular origin of the emission species based on ketonic defects, recent experimental results suggested the necessity of excimer formation between individual fluorenone units. We provide a range of new evidence supporting the monomolecular origin of green band emission in Polyfluorenes. Most importantly, we succeed in performing single-molecule spectroscopy on fluorenone-containing Polyfluorene model compounds. Whereas most fluorenone-containing molecules exhibit both blue backbone and green fluorenone emission independent of fluorenone concentration, it is the relative intensities of the two species which correlate strongly with the fluorenone concentration on the single-molecule level. Furthermore, we consider a novel model compound with a bifacial arrangement of two fluorenone units. This compound does not provide any signatures of enhanced intramolecular excimer formation but does strongly indicate that concentration quenching effects occur once fluorenone units can interact electronically. The ability to detect on-chain defect emission in a single polymer molecule demonstrates that photochemical reactions in conjugated polymers can be monitored by fluorescence spectroscopy down to the level of a few atoms, constituting an unprecedented degree of materials characterization.
-
Comprehensive photophysical studies of Polyfluorenes containing on-chain emissive defects
Physical Review B, 2005Co-Authors: Christoph Gadermaier, Ullrich Scherf, Emil J. W. List, Lorenz Romaner, T. Piok, B. Souharce, Giulio Cerullo, Guglielmo LanzaniAbstract:We present a comprehensive study of the photoexcitation dynamics in fluorenone-free and fluorenone-containing Polyfluorenes both on the femtosecond and the millisecond time scale. In the fluorenone-free Polyfluorene a small amount of polarons are observed, which form instantaneously. Triplets are the dominant species on the ms time scale. In fluorenone-containing Polyfluorenes a considerable fraction of the excitation energy is transferred to the fluorenone units, which act as energy sinks. Their lowest excited state is of charge-transfer nature and can dissociate into polarons, while no triplets are revealed.
-
Emission properties of pristine and oxidatively degraded Polyfluorene type polymers
physica status solidi (a), 2004Co-Authors: Stefan Gamerith, Christoph Gadermaier, Ullrich Scherf, Emil J. W. ListAbstract:We present a detailed and comprehensive picture of the photophysics including device applications within the Polyfluorene family of conjugated polymers. First, the photophysics of pristine Polyfluorenes in solution and film is outlined, including a discussion of the so-called β-phase, which is characterised by a more planar ground state configuration. Particular attention is also dedicated to the occurence of low energy emission bands, which often deteriorate the initially blue emission of Polyfluorenes, especially in electroluminescent devices. Although the origin of these emission features has been the object of a controversial discussion, strong evidence for our current ascription to emissive on-chain fluorenone defects is given also in contrast to previous assignments to aggregates, excimers, or exciplexes. According to the current attribution fluorenone-containing Polyfluorenes can be described as a guest host system. Following this picture the photoexcitation dynamics from the fs to the ms regime is outlined. Finally, polymer light emitting diodes (PLEDs) based on Polyfluorene-type emitters are discussed, especially related to their degradation mechanisms and possible remedies provided by chemistry to reduce the oxidative degradation of Polyfluorene-based PLEDs. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
-
The Origin of Green Emission in Polyfluorene‐Based Conjugated Polymers: On‐Chain Defect Fluorescence
Advanced Functional Materials, 2003Co-Authors: Lorenz Romaner, Ullrich Scherf, Alexander Pogantsch, P. Scandiucci De Freitas, Martin Gaal, Egbert Zojer, Emil J. W. ListAbstract:The low emission band at 2.2–2.3 eV in Polyfluorene-based conjugated materials is studied by various spectroscopic methods on defined copolymers of 9–9′-difarnesyl-fluorene with 9-fluorenone, which can be seen as a model compound for degraded Polyfluorenes. Absorption, electroluminescence, and photoluminescence in the film (temperature-dependent) and solution (room temperature) reveal the optical properties of this low-energy emission band emerging in Polyfluorene-type polymers upon degradation. All the experimental evidence presented yield direct evidence against excimer or aggregate formation as the primary source of the low-energy emission band. Instead keto defect sites can be shown to be responsible for the emissive defect.
John M. Lupton - One of the best experts on this subject based on the ideXlab platform.
-
Single molecule spectroscopy of Polyfluorenes
Polyfluorenes, 2008Co-Authors: Enrico Da Como, Klaus Becker, John M. LuptonAbstract:Single molecule spectroscopy resolves some of the crucial issues in the photophysics of Polyfluorenes. After an introduction on single molecule spectroscopy we present the ability of this technique in revealing the intramolecular nature of the photophysical phenomena encountered in the different phases of Polyfluorene and in fluorenone–fluorene copolymers. First, we correlate the peculiar emission properties of the phases to their chain extension, probed by using polarisation sensitive studies. Moreover, by looking at single chromophores in the β phase, we demonstrate how a slight bending in this one-dimensional structure does not disrupt the π conjugation while impacting on the exciton linewidth, a crucial parameter for the comprehension of energy and charge transfer. As a definitive answer to the colour degradation, we report the single chain spectroscopy of fluorenone–fluorene copolymers, demonstrating the monomolecular origin of the green emission. More generally, the presented experiments illustrate the unique possibilities offered by single molecule spectroscopy in correlating the structure and the resulting electronic properties in conjugated polymers.
-
on chain fluorenone defect emission from single Polyfluorene molecules in the absence of intermolecular interactions
Advanced Functional Materials, 2006Co-Authors: K D Becker, John M. Lupton, Benjamin S. Nehls, Jochen Feldmann, Frank Galbrecht, Deqing Gao, Ullrich ScherfAbstract:The emission of semiconducting Polyfluorenes is often accompanied by an undesired feature in the green spectral region. Whereas a number of previous investigations have argued in favor of a monomolecular origin of the emission species based on ketonic defects, recent experimental results suggested the necessity of excimer formation between individual fluorenone units. We provide a range of new evidence supporting the monomolecular origin of green band emission in Polyfluorenes. Most importantly, we succeed in performing single-molecule spectroscopy on fluorenone-containing Polyfluorene model compounds. Whereas most fluorenone-containing molecules exhibit both blue backbone and green fluorenone emission independent of fluorenone concentration, it is the relative intensities of the two species which correlate strongly with the fluorenone concentration on the single-molecule level. Furthermore, we consider a novel model compound with a bifacial arrangement of two fluorenone units. This compound does not provide any signatures of enhanced intramolecular excimer formation but does strongly indicate that concentration quenching effects occur once fluorenone units can interact electronically. The ability to detect on-chain defect emission in a single polymer molecule demonstrates that photochemical reactions in conjugated polymers can be monitored by fluorescence spectroscopy down to the level of a few atoms, constituting an unprecedented degree of materials characterization.
-
Transient electroluminescence spectroscopy of Polyfluorene light-emitting diodes
Synthetic Metals, 2003Co-Authors: John M. Lupton, Jan KleinAbstract:We present transient electroluminescence spectra of Polyfluorene light-emitting diodes. The luminescence spectra recorded after switch-off of a 5 V driving pulse exhibit a dynamic change with time. A study of the temperature and bias offset dependence reveals that charge carriers are preferentially trapped on low energy oxidative sites present on the Polyfluorene backbone. These observations of the charge carrier dynamics in light-emitting diodes (LEDs) compare to recent results on exciton trapping on emissive intra-chain defects in Polyfluorenes.
-
Transient electroluminescence spectroscopy of Polyfluorene light-emitting diodes
Synthetic Metals, 2003Co-Authors: John M. Lupton, Jan KleinAbstract:We present transient electroluminescence spectra of Polyfluorene light-emitting diodes. The luminescence spectra recorded after switch-off of a 5 V driving pulse exhibit a dynamic change with time. A study of the temperature and bias offset dependence reveals that charge carriers are preferentially trapped on low energy oxidative sites present on the Polyfluorene backbone. These observations of the charge carrier dynamics in light-emitting diodes (LEDs) compare to recent results on exciton trapping on emissive intra-chain defects in Polyfluorenes.
