958 research outputs found

    Een balie met stamboom: de woelige eerste decennia van de Gentse orde van advocaten

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    Three articles on the first decennies of the Ghent bar of lawyers: - The establishment of the Ghent bar in 1812, under the Napoleonic decree of 1810; - The attitude of king William and his minister of Justice towards advocates (1815-1830); - Orangists at the Ghent bar in the first years of Belgium's independence

    Enhance performance of organic solar cells based on an isoindigo-based copolymer by balancing absorption and miscibility of electron acceptor

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    Superior absorption of PC(71)BM in visible region to that of PC(61)BM makes PC(71)BM a predominant acceptor for most high efficient polymer solar cells (PSCs). However, we will demonstrate that power conversion efficiencies (PCEs) of PSCs based on poly[N,N'-bis(2-hexyldecyl)isoindigo-6, 6'-diyl-alt-thiophene-2,5-diyl] (PTI-1) with PC(61)BM as acceptor are 50% higher than their PC71BM counterparts under illumination of AM1.5G. AFM images reveal different topographies of the blends between PTI-1:PC(61)BM and PTI-1:PC(71)BM, which suggests that acceptor's miscibility plays a more important role than absorption. The photocurrent of 9.1 mA/cm(2) is among the highest value in PSCs with a driving force for exciton dissociation less than 0.2 eV

    High-entropy mixtures of pristine fullerenes for solution-processed transistors and solar cells

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    The solubility of pristine fullerenes can be enhanced by mixing C-60 and C-70 due to the associated increase in configurational entropy. This "entropic dissolution" allows the preparation of field-effect transistors with an electron mobility of 1 cm(2) V-1 s(-1) and polymer solar cells with a highly reproducible power-conversion efficiency of 6%, as well as a thermally stable active layer.Funding Agencies|Swedish Research Council, Formas; Chalmers Area of Advance Energy; Knut and Alice Wallenberg Foundation through two Wallenberg Academy Fellowships; European Research Council (ERC) [637624]</p

    Diffusion-enhanced exciton dissociation in single-material organic solar cells

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    Single-material organic solar cells have recently attracted research attention due to their simplicity, morphological robustness and high yield of exciton dissociation. Using α-sexithiophene as a model system, we show that the single-event probability of the exciton dissociation at the boundaries of polycrystalline domains with different molecular orientation is extremely low (∼0.5%), while a high efficiency of charge generation is gained via hundred-fold crossings of the domain boundaries due to the long exciton diffusion length (∼45 nm). This journal i

    Exciton diffusion length and charge extraction yield in organic bilayer solar cells

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    The authors thank the German BMBF for funding within the scope of the projects InnoProfile 2.2 (03IPT602X) and MEDOS (03EK3503A) as well as the European Commission within the scope of the Career Integration Grant (FP7, MSCA, 630864). I.D.W.S. and M.T.S. acknowledge support from the European Research Council (grant number 321305) and from EPSRC (grant number EP/L017008/1). I.D.W.S. also acknowledges a Royal Society Wolfson Research Merit Award. K.L. is a fellow of the Canadian Institute for Advanced Research (CIFAR). The research data supporting this publication can be accessed at https://doi.org/10.17630/af263bfb-620c-40a8-9929-86658e5187d3A method for resolving the diffusion length of excitons and the extraction yield of charge carriers is presented based on the performance of organic bilayer solar cells and careful modeling. The technique uses a simultaneous variation of the absorber thickness and the excitation wavelength. Rigorously differing solar cell structures as well as independent photoluminescence quenching measurements give consistent results.PostprintPostprintPeer reviewe

    Charge Transport in Pure and Mixed Phases in Organic Solar Cells

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    In organic solar cells continuous donor and acceptor networks are consid- ered necessary for charge extraction, whereas discontinuous neat phases and molecularly mixed donor–acceptor phases are generally regarded as detrimental. However, the impact of different levels of domain continuity, purity, and donor–acceptor mixing on charge transport remains only semi- quantitatively described. Here, cosublimed donor–acceptor mixtures, where the distance between the donor sites is varied in a controlled manner from homogeneously diluted donor sites to a continuous donor network are studied. Using transient measurements, spanning from sub-picoseconds to micro- seconds photogenerated charge motion is measured in complete photovoltaic devices, to show that even highly diluted donor sites (5.7%–10% molar) in a buckminsterfullerene matrix enable hole transport. Hopping between isolated donor sites can occur by long-range hole tunneling through several buckmin- sterfullerene molecules, over distances of up to ≈4 nm. Hence, these results question the relevance of “pristine” phases and whether a continuous interpen- etrating donor–acceptor network is the ideal morphology for charge transport
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