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Now showing items 1 - 16 of 158

  • Malcolm Williamson: A Mischievous Museby Anthony Meredith; Paul Harris

    Review by: Paul Conway  

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  • Malcolm Arnold: Rogue Geniusby Anthony Meredith; Paul Harris

    Review by: Stephen Town  

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  • Malcolm Arnold: Rogue Geniusby Anthony Meredith; Paul Harris

    Review by: Stephen Town  

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    A narrowband photodetector for detecting radiation in a spectral window, the narrowband photodetector comprising a first electrode that is at least partially transparent to radiation, a second electrode and a photoactive layer that is coated onto at least one of the first electrode, the second electrode and at least one interlayer disposed on at least one of the first and second electrodes. The photoactive layer is provided at least partially between the first and second electrodes, generates charge carriers in response to radiation incident thereon through the first electrode and has an absorption coefficient profile and thickness selected so that radiation in a first spectral window leads to volume generation of charge carriers substantially throughout the photoactive layer and radiation in a second spectral window different to the first spectral window leads to surface generation of charge carriers proximate the first electrode. The photoactive later also has a mobility for charge carriers, such that for an applied voltage across the electrodes, the extraction of surface generated charge carriers is suppressed so that the photodetector shows a photoresponse to radiation in the first spectral window and includes at least one of an inorganic semiconductor and an organic -inorganic hybrid semiconductor.
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  • Cavity Enhanced Organic Photodiodes with Charge Collection Narrowing

    Yazmaciyan, Aren   Meredith, Paul   Armin, Ardalan  

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  • Accurate characterization of next-generation thin-film photodetectors

    Fang, Yanjun   Armin, Ardalan   Meredith, Paul   Huang, Jinsong  

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  • On the Electro‐Optics of Carbon Stack Perovskite Solar Cells

    Kerremans, Robin   Sandberg, Oskar J.   Meroni, Simone   Watson, Trystan   Armin, Ardalan   Meredith, Paul  

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  • Melanin biopolymers: tailoring chemical complexity for materials design

    d'Ischia, Marco   Napolitano, Alessandra   Pezzella, Alessandro   Meredith, Paul   Buehler, Markus J  

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  • Decoupling Ionic and Electronic Currents in Melanin

    Sheliakina, Margarita   Mostert, Albertus Bernardus   Meredith, Paul  

    Melanin, the human skin pigment, has emerged as a model material for bioelectronic interfaces due to its biocompatibility, ability to be processed into electronic-device-grade thin films, and transducing charge transport properties. These charge transport properties have been suggested to be of a mixed protonic/electronic nature, regulated by a redox reaction that can be manipulated by changing the material's hydration state. However, to date, there are no detailed reports which clarify, quantify, or disentangle the protonic and electronic contributions to long-range current conduction in melanin. Described herein, is a systematic hydration controlled electrical study on synthetic melanin thin films utilizing impedance/dielectric spectroscopy, which rationally investigates the protonic and electronic contributions. Through modeling and inspecting the frequency dependent behavior, it is shown that the hydration dependent charge transport is due to proton currents. Results show a real dielectric constant for hydrated melanin of order approximate to 1 x 10(3). Surprisingly, this very high value is maintained over a wide frequency range of approximate to 20-10(4) Hz. The electronic component appears to have little influence on melanin's hydration dependent conductivity: thus the material should be considered a protonic conductor, and not as previously suggested, a mixed protonic/electronic hybrid.
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  • The photoreactive free radical in eumelanin.

    Mostert, Albertus B   Rienecker, Shermiyah B   Noble, Christopher   Hanson, Graeme R   Meredith, Paul  

    Melanin is the primary photoprotecting pigment in humans as well as being implicated in the development of deadly melanoma. The material also conducts electricity and has thus become a bioelectronic model for proton-to-electron transduction. Central to these phenomena are its spin properties-notably two linked species derived from carbon-centered and semiquinone radicals. Using a novel in situ photoinduced electron paramagnetic resonance technique with simultaneous electrical measurements, we have elucidated for the first time the distinct photoreactivity of the two different radical species. We find that the production of the semiquinone is light- and water-driven, explaining the electrical properties and revealing biologically relevant photoreactivity.=20
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  • Considerations for Upscaling of Organohalide Perovskite Solar Cells

    Lin, Qianqian   Nagiri, Ravi Chandra Raju   Burn, Paul L.   Meredith, Paul  

    Thin film organohalide lead perovskite-based solar cells have emerged over the last five years as a potentially low-cost, low-embedded-energy and high-efficiency photovoltaic technology. However, almost all reported high-efficiency devices have small active areas significantly less than 1 cm(2). Upscaling of organohalide lead perovskite solar cells is now required for successful manufacturing and commercialization. In this work, three generic design rules for large area devices are proposed. Using these design rules, high efficiency large area (2.0 cm(2)) cells are demonstrated based on a predictive methodology incorporating the optoelectronic design of highly transparent and conductive electrodes, and controlled crystal size and uniformity of the organohalide perovskite junction. These optimized large area monolithic solar cells show power conversion efficiencies (PCEs) >12%, with an enhanced open-circuit voltage (V-oc) of 1.02 V and respectable fill factor (FF) of 0.61.
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  • The authors reply

    Redfern, Oliver C.   Smith, Gary B.   Prytherch, David R.   Meredith, Paul   Inada-Kim, Matthew   Schmidt, Paul E.  

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  • A thiocarbonyl-containing small molecule for optoelectronics

    Gendron, David   Maasoumi, Fatemeh   Armin, Ardalan   Pattison, Katherine   Burn, Paul L.   Meredith, Paul   Namdas, Ebinazar B.   Powell, Benjamin J.  

    We report the synthesis and characterization of a novel thiocarbonyl iso-DPP derivative, namely 1,3,4,6-tetraphenylpyrrolo[3,2-b]pyrrole-2,5(1H, 4H)-dithione. Even without solubilising alkyl chains, the small molecule could be processed from organic solvents such as dichloromethane, chloroform or dichlorobenzene, and it was found that the optical properties of neat thin films were strongly dependent on the solvent used. Field effect hole mobilities were of the order 10(-4) cm(2) V-1 s(-1), with mobilities measured in a diode configuration solvent dependent and at least an order of magnitude lower. Importantly, blends of the iso-DPP derivative with PC70BM, a typically used electron acceptor in bulk heterojunction solar cells, were found to possess hole mobilities of up to 10(-3) cm(2) V-1 s(-1) in a diode configuration, which was an order of magnitude larger than the electron mobility. Finally, simple bulk heterojunction solar cells were fabricated with maximum power conversion efficiencies of 2.3%.
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  • Engineering dielectric constants in organic semiconductors

    Armin, Ardalan   Stoltzfus, Dani M.   Donaghey, Jenny E.   Clulow, Andrew J.   Nagiri, Ravi Chandra Raju   Burn, Paul L.   Gentle, Ian R.   Meredith, Paul  

    The dielectric properties of three pairs of organic semiconductors that contain increasing numbers of cyclopentadithiophene-co-benzothiadiazole moieties (monomer, dimer and polymer) were studied and compared. The materials in each pair differed in the nature of the 'solubilizing groups', which are either alkyl- or glycol-based. At low frequencies (
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  • Anomalous Exciton Quenching in Organic Semiconductors in the Low-Yield Limit

    Zarrabi, Nasim   Yazmaciyan, Aren   Meredith, Paul   Kassal, Ivan   Armin, Ardalan  

    The dynamics of exciton quenching are critical to the operational performance of organic optoelectronic devices, but their measurement and elucidation remain ongoing challenges. Here, we present a method for quantifying small photoluminescence quenching efficiencies of organic semiconductors under steady-state conditions. Exciton quenching efficiencies of three different organic semiconductors, PC70BM, P3HT, and PCDTBT, are measured at different bulk quencher densities under continuous low-irradiance illumination. By implementing a steady-state bulk-quenching model, we determine exciton diffusion lengths for the studied materials. At low quencher densities we find that a secondary quenching mechanism is in effect, which is responsible for approximately 20% of the total quenched excitons. This quenching mechanism is observed in all three studied materials and exhibits quenching volumes on the order of several thousand cubic nanometers. The exact origin of this quenching process is not clear, but it may be indicative of delocalized excitons being quenched prior to thermalization.
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  • Efficient, monolithic large area organohalide perovskite solar cells

    Hambsch, Mike   Lin, Qianqian   Armin, Ardalan   Burn, Paul L.   Meredith, Paul  

    Solar cells based on organohalide perovskites (PSCs) have made rapid progress in recent years and are a promising emerging technology. An important next evolutionary step for PSCs is their up-scaling to commercially relevant dimensions. The main challenges in scaling PSCs to be compatible with current c-Si cells are related to the limited conductivity of the transparent electrode, and the processing of a uniform and defect-free organohalide perovskite layer over large areas. In this work we present a generic and simple approach to realizing efficient solution-processed, monolithic solar cells based on methylammonium lead iodide (CH3NH3PbI3). Our devices have an aperture area of 25 cm(2) without relying on an interconnected strip design, therefore reducing the complexity of the fabrication process and enhancing compatibility with the c-Si cell geometry. We utilize simple aluminum grid lines to increase the conductivity of the transparent electrode. These grid lines were exposed to an UV-ozone plasma to grow a thin aluminum oxide layer. This dramatically improves the wetting and film forming of the organohalide perovskite junction on top of the lines, reducing the probability of short circuits between the grid and the top electrode. The best devices employing these modified grids achieved power conversion efficiencies of up to 6.8%.
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