White emitting polyfluorene functionalized with azide hybridized on near-UV light emitting diode for high color rendering index

Huyal, Ilkem Ozge; Özel, Tuncay; Koldemir, Ünsal; Nizamoğlu, Sedat; Tuncel, Dönüş; Demir, Hilmi Volkan

doi:10.1364/oe.16.001115

Cited by 26 publications

(27 citation statements)

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“…To this end, recently we have reported the white light generation ability of azide functionalized polyfluorene (poly[(9,9-dihexylfluorene)-co-alt-(9,9-bis(6-azidohexyl)fluorene)], PFA) by its hybridization on an InGaN/GaN based n-UV LED. 21 The integration of the single PFA layer onto the inorganic n-UV LED platform enabled the generation of high quality white light with colour rendering index as high as 91. We also reported on the high fluorescence quantum efficiency of PFA which we used for the preparation of hybrid organic/inorganic devices.…”

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On the origin of high quality white light emission from a hybrid organic/inorganic light emitting diode using azide functionalized polyfluorene

et al. 2008

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High quality white light generation with high colour rendering index (CRI) was achieved by integrating a cross-linkable azide functionalized polyfluorene derivative, namely poly[(9,9-dihexylfluorene)-co-alt-(9,9-bis(6-azidohexyl) fluorene)] (PFA), as a down-converting fluorescent material on the inorganic n-UV InGaN/GaN LED platform. For comparison, two other polyfluorene based polymers, namely poly[(9,9-dihexylfluorene)-co-alt-(9,9-bis(6-bromohexyl) fluorene)] (PFB) and poly[9,9-dihexyl-9H-fluorene] (PF), were tested for white light generation. While PFA and PF both led to white light generation, PFB fell out of the white region on the chromaticity diagram. Compared to PFA, both of the control groups (PF and PFB) exhibited much lower CRI. To gain a better insight into the mechanisms playing a key role for the generation of such high quality white light in PFA, all of these polymers were further subjected to a series of experiments such as controlled exposure to heat at 220 °C for 2 h under Ar and in air. The polymers PFA and PFB, which include cross-linkable groups, produced broad emission spectra in the region of 430-650 nm upon annealing in the absence of oxygen under Ar atmosphere while almost no change was observed in the emission spectrum of PF without any cross-linkable groups. PFA undergoes cross-linking through the decomposition of azide leading to reactive nitrene species, whereas in PFB cross-linking probably occurs via debromination. This result clearly proved that the broadening can not be attributed only to photo or thermal oxidation, but it is also due to cross-linking. PFA was also exposed to n-UV light from the InGaN/GaN LED to investigate its photostability. In these experiments, the spectral changes in absorbance and emission properties and thermal transitions of these polymers were monitored by FT-IR, UV-Vis and fluorescent spectrometry, and differential scanning calorimetry (DSC). These experiments indicated that PFA provides high quality white light opportunely via cross-linking and remains stable once cross-linking is formed in a solid film. © 2008 The Royal Society of Chemistry

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On the origin of high quality white light emission from a hybrid organic/inorganic light emitting diode using azide functionalized polyfluorene

et al. 2008

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“…Fluorene-based polymers have been extensively investigated because of their superior optoelectronic properties to be utilized in various photonic device applications [1][2][3][4][5][6]. Of such π -conjugated systems, poly(9,9-dialkylfluorene)s are particularly attractive as blue emitters in organic light emitting diodes (OLEDs), thanks to their high quantum efficiency, ease of processability, and good thermal stability [2].…”

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Quantum efficiency enhancement in film by making nanoparticles of polyfluorene

Huyal¹,

Özel²,

Tuncel³

et al. 2008

Opt. Express

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Abstract:We report on conjugated polymer nanoparticles of polyfluorene that were formed to exhibit higher fluorescence quantum efficiency in film (68%) and reduce undesired emission peak wavelength shifts in film (by 20 nm), compared to the solid-state polymer thin film made directly out of the same polymer solution without forming nanoparticles. Using the facile reprecipitation method, solutions of poly[9,9-dihexyl-9H-fluorene] in THF were added at different volume ratios to obtain different size distributions of nanoparticle dispersions in water. This allowed us to control the sizedependent optical emission of our polyfluorene nanoparticles. Such organic nanoparticles hold great promise for use as efficient emitters in optoelectronic device applications.

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“…PF3B was synthesized using the similar procedure as previously reported. 32,33 However, in this synthesis, 2,7-dibromo-9,9-bis(3-bromopropyl)-9H-fluorene was used: yield 57%; , CH 3 ); gel permeation chromatography (GPC) M n = 0.6 Â 10 4 g mol À1 , M w = 1.6 Â 10 4 g mol À1 (THF was used as a solvent and polystyrene as standard).…”

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White-Emitting Conjugated Polymer Nanoparticles with Cross-Linked Shell for Mechanical Stability and Controllable Photometric Properties in Color-Conversion LED Applications

et al. 2011

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W ater-soluble conjugated polymers have been receiving increasingly greater attention owing to their potential applications in the areas of biosensing, bioimaging, and optoelectronics. For example, they have been successfully utilized in the biosensor applications to detect proteins, nucleic acids, and sugars. 1À6 These polymers can be prepared by attaching ionic side groups to the polymer backbone. However, their synthesis is tedious and their solubility is still limited in the water. Good water solubility or dispersibility of the conjugated polymers can alternatively be achieved by converting them into nanoparticles. 7À13 Such water-dispersible conjugated polymer nanoparticles (CPNs) have been exploited in different applications. For example, Landfester, Sherf, List, and coworkers have demonstrated the use of CPNs in optoelectronic applications including light-emitting diodes and photovoltaics and also as inks in inkjet printing. 14À19 Foulger and co-workers demonstrated the use of hybrid conjugated polymer nanoparticles composed of blue-and green-emitting polymers in the construction of organic light-emitting diodes (OLEDs). 20 The color tuning of the electroluminescence for the devices was achieved through energy transfer. These nanoparticles have also been used in biological applications such as fluorescent images, biosensors, and oxygen sensors. 21À27 Apart from these applications, color tuning is important for the optoelectronic applications, especially for energyefficient indoor and outdoor lighting. 28,29 Water-dispersible conjugated polymer nanoparticles can be prepared mainly by two methods, which are miniemulsion and reprecipitation. In the miniemulsion method, a two-phase system (oil-in-water) is used. 7,8 The polymer is dissolved in an organic solvent, which is not miscible with water, and added into a surfactant containing aqueous solution while sonicating. After the nanoparticle formation, the organic solvent is evaporated off to leave behind the conjugated nanoparticles stabilized by the surfactant. In the reprecipitation method, the polymer is dissolved in an organic * Address correspondence to dtuncel@fen.bilkent.edu.tr, volkan@bilkent.edu.tr.Received for review July 9, 2010 and accepted March 28, 2011. Published online 10.1021/nn103598qABSTRACT We report on the synthesis and characterization of water-dispersible, mechanically stable conjugated polymer nanoparticles (CPNs) in shelled architecture with tunable emission and controllable photometric properties via cross-linking. Using a reprecipitation method, whiteemitting polymer nanoparticles are prepared in different sizes by varying the concentration of polymer; the emission kinetics are tuned by controlling the shell formation. For this purpose, polyfluorene derivatives containing azide groups are selected that can be decomposed under UV light to generate very reactive species, which opportunely facilitate the inter-and intra-cross-linking of polymer chains to form shells. Nanoparticles before and after UV treatment are characterized by v...

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White emitting polyfluorene functionalized with azide hybridized on near-UV light emitting diode for high color rendering index

Cited by 26 publications

References 12 publications

On the origin of high quality white light emission from a hybrid organic/inorganic light emitting diode using azide functionalized polyfluorene

On the origin of high quality white light emission from a hybrid organic/inorganic light emitting diode using azide functionalized polyfluorene

Quantum efficiency enhancement in film by making nanoparticles of polyfluorene

White-Emitting Conjugated Polymer Nanoparticles with Cross-Linked Shell for Mechanical Stability and Controllable Photometric Properties in Color-Conversion LED Applications

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