Co-self-assembly of mesostructured silica films from solutions of tetrahydrofuran (THF) and water, silica precursor species, and structure-directing Pluronic P123 block-copolymer molecules is reported with and without conjugated polymer guest species. The solution-phase behavior of the ternary THF-water-P123 system guided the selection of nonequilibrium synthesis conditions that allowed highly ordered 2D hexagonal or lamellar mesostructured silica to be prepared. Dilute water molecules produced in situ by silica condensation were necessary and sufficient to promote P123 self-aggregation into micelles and ultimately liquid crystal-like inorganic-organic mesophases as the THF evaporated. Solid-state twodimensional 13 C{ 1 H} and 29 Si{ 1 H} NMR characterization of the product film materials revealed highly mobile block copolymer components at room temperature and preferential interactions of poly(ethylene oxide) moieties with the silica framework at 260 K. Solution processing in THF permitted highly hydrophobic, high molecular weight, conjugated polymers to be directly coassembled within the mesostructured inorganic-organic host matrices during their formation. The incorporated conjugated polymers exhibited semiconducting properties and enhanced environmental photo-stability that may be exploited in electronic and optoelectronic devices.
In this study a blue‐light‐emitting conjugated polymer, poly(9,9‐dioctylfluorene), is confined to the interlayer space of inorganic, layered metal dichalcogenide materials, metallic MoS2, and semiconducting SnS2. The nanocomposites are prepared through Li intercalation into the inorganic compound, exfoliation, and restacking in the presence of the polymer. X‐ray diffraction and optical absorption measurements indicate that a single conjugated polymer monolayer, with an overall extended planar morphology conformation, is isolated between the inorganic sheets, so that polymer aggregation or π–π interchain interactions are significantly reduced. Photoluminescence (PL) measurements show that the appearance of the undesirable green emission observed in pristine polymer films is suppressed by incorporating the polymer into the inorganic matrix. The blue emission of the intercalated polymer is stable for extended periods of time, over two years, under ambient conditions. Furthermore, the green emission is absent in the PL spectra of nanocomposite films heated at 100 °C for 7 h in air with direct excitation of the keto defect. Finally, no green emission was observed in the electroluminescence spectrum of light‐emitting devices fabricated with a polymer‐intercalated SnS2 nanocomposite film. These results support the proposed hypothesis that fluorenone defects alone are insufficient to generate the green emission and that interchain interactions are also required.
The quest for alternative energy sources has generated a world-wide effort to prepare materials and devices designed to harvest clean abundant energy resources such as solar radiation. Considerable interest has focused on hybrid photovoltaic systems combining an organic chromophore, conjugated polymer or dye, and an n-type inorganic semiconductor. [1][2][3] A suitable energy band offset between the organic and inorganic components ensures that photo-excited electronhole pairs formed near the organic/inorganic interface will dissociate into free carriers, with the electrons preferably on one component and the holes on the other. A promising hybrid donor-acceptor pair for photovoltaics are poly(p-phenylene vinylene) (PPV)-type conjugated polymers and titanium dioxide, [4,5] owing to the high optical absorption of the polymer in the visible range and the band offset at the titania/PPV interface, which induces electron transfer from the photo-excited polymer to titanium dioxide. To provide efficient exciton dissociation into charges prior to recombination, the phase separation between the organic and inorganic species must be on the same scale as the polymer exciton diffusion length, that is, 8-20 nm. [6,7] Furthermore, carrier transport to the electrodes requires that the organic and inorganic phases form continuous networks through the entire film.[8] The challenge is, therefore, to direct a donor-acceptor organic-inorganic phase separation on a sub-20 nm length scale, and at the same time obtain continuity and orientation of each individual phase on a much longer length scale. To achieve this goal we developed a new and general synthetic approach that employs the co-assembly of a titania precursor species, a conjugated polymer, and an amphiphilic structure-directing agent to form conjugated-polymerincorporated mesoscopically ordered titania films. The use of non-aqueous synthetic conditions enabled, for the first time, the incorporation of the highly hydrophobic conjugated polymers within the mesostructured titania host matrix during its formation. Judicious selection of the surface-active agent type and concentration directed the deposition of a cubically ordered through-film interpenetrating titania and semiconducting polymer networks with ca. 15 nm organic-inorganic phase separation. Incorporation of the conjugated polymer into the 3D titania matrix enhances its photostability, and integration of the novel hybrid material into a photovoltaic device results in improved device performances. This study demonstrates the ability to direct the self-organization of functional components into hierarchically ordered materials with improved characteristics for electronic and opto-electronic applications.Several approaches have been previously applied to prepare nanoscale interpenetrating conjugated-polymer/titania networks, but they typically lack at least one of the important characteristics, that is, the sub-20 nm organic-inorganic phase separation or the through-film connectivity. Mixing the semiconducting polymers wi...
The generation of white light requires the combination of two or more chromophores that emit simultaneously. The observed color of a mixture of light-emitting molecules, however, originates generally only from the lowest band-gap species because of efficient energy transfer between the chromophores which is difficult to avoid. Here we report on a nanocomposite material designed to yield pure and stable white photo- and electroluminescence. In this material, red, green, and blue emitting conjugated polymers are confined within the galleries of a layered semiconducting host matrix. The host hinders polymer pi-pi interactions which are responsible for the energy transfer between polymer chains, consequently, emission from the three chromophores is observed simultaneously resulting in white photoluminescence. The efficacy of the nanocomposites is demonstrated in simple single-layer white-emitting polymer diodes. The mechanism suggested here for white light generation, supported by extensive luminescence measurements, is in contrast to that previously reported in white-emitting polymer diodes where efficient energy transfer between polymer chains was essential for obtaining white light.
Users may download and print one copy of any publication from the public portal for the purpose of private study or research. You may not further distribute the material or use it for any profit-making activity or commercial gain You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.
Users may download and print one copy of any publication from the public portal for the purpose of private study or research. You may not further distribute the material or use it for any profit-making activity or commercial gain You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.