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Your search keyword '"Koster, L. J. A."' showing total 38 results
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38 results on '"Koster, L. J. A."'

1. Spatial modeling of the 3D morphology of hybrid polymer-ZnO solar cells, based on electron tomography data

Author

Stenzel, O., Schmidt, V., Hassfeld, H., Thiedmann, R., Koster, L. J. A., Oosterhout, S. D., van Bavel, S. S., Wienk, M. M., Loos, J., and Janssen, R. A. J.

Subjects
Statistics - Applications, Condensed Matter - Materials Science, Condensed Matter - Soft Condensed Matter
Abstract

A spatial stochastic model is developed which describes the 3D nanomorphology of composite materials, being blends of two different (organic and inorganic) solid phases. Such materials are used, for example, in photoactive layers of hybrid polymer zinc oxide solar cells. The model is based on ideas from stochastic geometry and spatial statistics. Its parameters are fitted to image data gained by electron tomography (ET), where adaptive thresholding and stochastic segmentation have been used to represent morphological features of the considered ET data by unions of overlapping spheres. Their midpoints are modeled by a stack of 2D point processes with a suitably chosen correlation structure, whereas a moving-average procedure is used to add the radii of spheres. The model is validated by comparing physically relevant characteristics of real and simulated data, like the efficiency of exciton quenching, which is important for the generation of charges and their transport toward the electrodes., Comment: Published in at http://dx.doi.org/10.1214/11-AOAS468 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org)

Published
2011
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3. Fully direct written organic micro-thermoelectric generators embedded in a plastic foil

Author

Massetti, Matteo, Bonfadini, S., Nava, D., Butti, M., Criante, L., Lanzani, G., Qiu, L., Hummelen, J. C., Liu, J., Koster, L. J. A., Caironi, M., Massetti, Matteo, Bonfadini, S., Nava, D., Butti, M., Criante, L., Lanzani, G., Qiu, L., Hummelen, J. C., Liu, J., Koster, L. J. A., and Caironi, M.

Abstract

Organic materials have attracted great interest for thermoelectric applications due to their tuneable electronic properties, solution processability and earth-abundance, potentially enabling high-throughput realization of low-cost devices for low-power energy harvesting applications. So far, organic thermoelectricity has primarily focused on materials development, with less attention given to integrated generators. Yet, future applications will require the combination of efficient generators architectures and scalable manufacturing techniques to leverage the advantages of such promising materials. Here we report the realization of a monolithic organic micro-thermoelectric generator (mu-OTEG), using only direct writing methods, embedding the thermoelectric legs within a plastic substrate through a combination of direct laser writing and inkjet printing techniques. Employing PEDOT:PSS for the p-type legs and a doped fullerene derivative for the n-type ones, we demonstrate a mu-OTEG with power density of 30.5 nW/cm(2) under small thermal gradients, proving the concrete possibility of achieving power requirements of low-power, distributed sensing applications., Funding Agencies|STW/NWOTechnologiestichting STWNetherlands Organization for Scientific Research (NWO) [VIDI 13476]; Foundation of Fundamental Research on Matter (FOM), Netherlands Organization for Scientific Research (NWO)

Published
2020
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5. The effect of morphology upon mobility: Implications for bulk heterojunction solar cells with nonuniform blend morphology.

Author

Groves, C., Koster, L. J. A., and Greenham, N. C.

Subjects
*MONTE Carlo method, *HETEROJUNCTIONS, *SOLAR cells, *PHOTOVOLTAIC power generation, *MORPHOLOGY
Abstract

We use a Monte Carlo model to predict the effect of composition, domain size, and energetic disorder upon the mobility of carriers in an organic donor-acceptor blend. These simulations show that, for the changes in local morphology expected within the thickness of a typical bulk heterojunction photovoltaic device, changes in mobility of more than an order of magnitude are expected. The impact of nonuniform mobility upon space-charge-limited diode and photovoltaic (PV) device performance is examined using a drift-diffusion model. The current passing through a space-charge-limited diode is shown to depend upon the position of the layers with differing mobility. Accurate modeling of the current in such devices can only be achieved using a drift-diffusion model incorporating nonuniform mobility. Inserting a 20 nm thick layer in which the mobility is less by one order of magnitude than in the rest of the 70 nm thick PV device reduced the device efficiency by more than 20%. Therefore it seems vital to exert a high degree of control over the morphology throughout the entire blend PV device, otherwise potential PV performance may be lost. [ABSTRACT FROM AUTHOR]

Published
2009
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7. Modeling the photocurrent of poly-phenylene vinylene/fullerene-based solar cells

Author

Koster, L J A, Mihailetchi, V D, Blom, P W M, Kafafi, ZH, and Lane, PA

Subjects
Photocurrent, Materials science, Organic solar cell, Poly(p-phenylene vinylene), organic solar cells, simulation, Molecular physics, Polymer solar cell, law.invention, charge transport, chemistry.chemical_compound, chemistry, law, Electric field, Solar cell, Organic chemistry, Charge carrier, photoconduction, Diffusion (business)
Abstract

We have studied the photocurrent data of 20:80 wt% blends of poly(2-methoxy-5-(3',7'-dimethyloctyloxy)-p-phenylene vinylene) (MDMO-PPV) and [6,6]-phenyl C-61-butyric acid methyl ester (PCBM) bulk heterojunction solar cells. Two cases have been investigated: When only drift of charge carriers is taken into account, a voltage-independent photocurrent is expected, corresponding to the extraction of all generated charges. It is demonstrated that the experimental data are in disagreement with this prediction. However, when both drift and diffusion of charges are taken into account, the predicted photocurrent shows a different behavior: At low electric fields a linear behavior is predicted, which results from the diffusion of charges, followed by saturation at high fields. The agreement between the numerical result and the experimental data obtained from MDMO-PPV:PCBM cells is satisfactory when a charge carrier generation rate of G=1.6 x 10(27) m(-3)s(-1) is used showing the importance of diffusion at low fields, i.e., near the open-circuit voltage.

Published
2004

11. Space-charge formation in thick MDMO-PPV

Author

Lenes, M., Mihailetchi, V. D., Koster, L. J. A., Blom, P. W. M., Heremans, PL, Muccini, M, and Meulenkamp, EA

Subjects
Materials science, Organic solar cell, business.industry, organic, polymer, fullerene, Energy conversion efficiency, Heterojunction, bulk heterojunction, Space charge, Polymer solar cell, recombination, Active layer, law.invention, solar cell, Optics, law, Solar cell, Optoelectronics, space-charge, Absorption (electromagnetic radiation), business
Abstract

One of the most studied systems in the field of organic photovoltaic devices are bulk heterojunction solar cells based on poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV) as electron donor and methano[60] fullerene [6,6]-phenyl C61 butyric acid methyl ester (PCBM) as electron acceptor. A striking feature of these types of solar cells is that at the optimal device thickness of typically 100 nm only 60% of the incident light is absorbed. It is evident that the absorption can be enhanced by increasing the thickness of the active layer. However, in spite of an increased absorption the overall power conversion efficiency shows a negative trend when increasing the device thickness beyond 100nm. From device point of view the reduced performance with increasing thickness mainly originates from a decrease of the fill factor. We demonstrate that this fill factor decrease is a result of the formation of space-charges in thick devices and charge recombination.

Published
2006

37. Effect of metal electrodes on the performance of polymer:fullerene bulk heterojunction solar cells.

Author

Mihaletchi, V. D., Koster, L. J. A., and Blom, P. W.

Subjects
*ELECTRODES, *SOLAR cells, *HETEROJUNCTIONS, *SEMICONDUCTOR junctions, *DIRECT energy conversion, *SOLAR energy
Abstract

An increase in the workfunction of the metal top electrode leads to a reduction of the open-circuit voltage, short-circuit current, and power conversion efficiency of organic bulk-heterojunction solar cells. It has been demonstrated that the photocurrent obtained from an active layer comprised of a blend of poly(2-methoxy-5-(3′,7′-dimethyloctyloxy)-p-phenylene vinylene) (OC1C10-PPV) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM), with lithium fluoride topped aluminum, silver, gold, or palladium electrodes, shows a universal behavior when scaled against the effective voltage across the device. Indeed, model calculations confirm that the dependence of the photocurrent on the effective voltage is responsible for the observed variation in performance of each different electrode. Consequently, for any given metal, only the device’s open-circuit voltage is required in order to be able to predict the remaining solar cell parameters. [ABSTRACT FROM AUTHOR]

Published
2004
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