The Experts below are selected from a list of 46548 Experts worldwide ranked by ideXlab platform
Paul W M Blom - One of the best experts on this subject based on the ideXlab platform.
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origin of the dark current ideality factor in polymer fullerene bulk heterojunction solar cells
Applied Physics Letters, 2011Co-Authors: Gertjan A H Wetzelaer, Martijn Lenes, Martijn Kuik, Paul W M BlomAbstract:In organic bulk heterojunction solar cells, a deviation of the ideality factor of the dark current from unity is commonly put forward as evidence for the presence of trap-assisted Recombination. We demonstrate that the non-ideality of the dark characteristics is determined by deeply trapped carriers in the transport-dominating constituent of the donor:acceptor blend, rather than a trap-assisted Recombination Mechanism. The light-intensity dependence of the open-circuit voltage confirms the absence of trap-assisted Recombination and demonstrates that the dominant Recombination Mechanism in the investigated polymer:fullerene solar cells is bimolecular. © 2011 American Institute of Physics.
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Optimum charge carrier mobility in organic solar cells
Applied Physics Letters, 2007Co-Authors: M. M. Mandoc, L. J. A. Koster, Paul W M BlomAbstract:In organic semiconductors the Recombination Mechanism is of the Langevin type, controlled by the mobility of the charge carriers. As a result, in organic solar cells the mobility simultaneously controls both the carrier extraction and the losses via carrier Recombination. The authors demonstrate that the balance between carrier losses by extraction and by Recombination leads to a distinct optimum in the carrier mobility with regard to the efficiency of organic solar cells. For low mobilities Recombination losses limit the performance, whereas the efficient extraction at high mobilities leads to a reduction of the open-circuit voltage.
Dandan Song - One of the best experts on this subject based on the ideXlab platform.
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dependence of carrier Recombination Mechanism on the thickness of the emission layer in green phosphorescent organic light emitting devices
Organic Electronics, 2011Co-Authors: Dandan Song, Qi Wang, Suling Zhao, Hany AzizAbstract:Abstract Delayed EL measurements are used to elucidate carrier Recombination and light emission Mechanism in phosphorescent organic light emitting devices (PhOLEDs) based on 4,4′-bis(9-carbazolyl)-1,1′-biphenyl (CBP) and fac-tris(2-phenylpyridine) iridium (Ir(ppy) 3 ) host:guest system. The results show that changing the thickness of the emitting layer (EML) leads to marked changes in charge-trapping and host–host triplet–triplet-annihilation (TTA) patterns, suggesting that carrier transport and Recombination processes change depending on EML thickness. The results suggest a change in carrier Recombination and exciton formation Mechanism, depending on EML thickness, from a scenario (for EMLs 20 nm) where carrier Recombination and exciton creation on the host is not negligible, and hence also the role of host-to-guest energy transfer.
Carol E Schrader - One of the best experts on this subject based on the ideXlab platform.
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igh chain class switch Recombination Mechanism and regulation
Journal of Immunology, 2014Co-Authors: Janet Stavnezer, Carol E SchraderAbstract:IgH class switching occurs rapidly after activation of mature naive B cells, resulting in a switch from expression of IgM and IgD to expression of IgG, IgE, or IgA; this switch improves the ability of Abs to remove the pathogen that induces the humoral immune response. Class switching occurs by a deletional Recombination between two switch regions, each of which is associated with a H chain constant region gene. Class switch Recombination (CSR) is instigated by activation-induced cytidine deaminase, which converts cytosines in switch regions to uracils. The uracils are subsequently removed by two DNA-repair pathways, resulting in mutations, single-strand DNA breaks, and the double-strand breaks required for CSR. We discuss several aspects of CSR, including how CSR is induced, CSR in B cell progenitors, the roles of transcription and chromosomal looping in CSR, and the roles of certain DNA-repair enzymes in CSR.
Yves Denizot - One of the best experts on this subject based on the ideXlab platform.
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comment on igh chain class switch Recombination Mechanism and regulation
Journal of Immunology, 2015Co-Authors: Alexis Saintamand, Jeanclaude Lecron, Franck Morel, Michel Cogne, Yves DenizotAbstract:Class switch Recombination (CSR) is a deletional DNA Recombination occurring in IgM+IgD+ B cells and overwhelmingly recognized for thereby generating IgG, IgA, and IgE Abs with the same antigenic specificity but new effector functions. In an interesting and well documented paper, Stavnezer and
Tomas Leijtens - One of the best experts on this subject based on the ideXlab platform.
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carrier trapping and Recombination the role of defect physics in enhancing the open circuit voltage of metal halide perovskite solar cells
Energy and Environmental Science, 2016Co-Authors: Tomas Leijtens, Henry J Snaith, Giles E Eperon, Alex J Barker, Giulia Grancini, Wei Zhang, James M Ball, Ajay Ram Srimath Kandada, Annamaria PetrozzaAbstract:One of the greatest attributes of metal halide perovskite solar cells is their surprisingly low loss in potential between bandgap and open-circuit voltage, despite the fact that they suffer from a non-negligible density of sub gap defect states. Here, we use a combination of transient and steady state photocurrent and absorption spectroscopy to show that CH3NH3PbI3 films exhibit a broad distribution of electron traps. We show that the trapped electrons recombine with free holes unexpectedly slowly, on microsecond time scales, relaxing the limit on obtainable open-circuit voltage (VOC) under trap-mediated Recombination conditions. We find that the observed VOCs in such perovskite solar cells can only be rationalized by considering the slow trap mediated Recombination Mechanism identified in this work. Our results suggest that existing processing routes may be good enough to enable open circuit voltages approaching 1.3 V in ideal devices with perfect contacts.
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high photoluminescence efficiency and optically pumped lasing in solution processed mixed halide perovskite semiconductors
Journal of Physical Chemistry Letters, 2014Co-Authors: Felix Deschler, Michael Price, S Pathak, Lina E Klintberg, Daviddominik Jarausch, Ruben Higler, Sven Huttner, Tomas Leijtens, Samuel D Stranks, Henry J SnaithAbstract:The study of the photophysical properties of organic–metallic lead halide perovskites, which demonstrate excellent photovoltaic performance in devices with electron- and hole-accepting layers, helps to understand their charge photogeneration and Recombination Mechanism and unravels their potential for other optoelectronic applications. We report surprisingly high photoluminescence (PL) quantum efficiencies, up to 70%, in these solution-processed crystalline films. We find that photoexcitation in the pristine CH3NH3PbI3–xClx perovskite results in free charge carrier formation within 1 ps and that these free charge carriers undergo bimolecular Recombination on time scales of 10s to 100s of ns. To exemplify the high luminescence yield of the CH3NH3PbI3–xClx perovskite, we construct and demonstrate the operation of an optically pumped vertical cavity laser comprising a layer of perovskite between a dielectric mirror and evaporated gold top mirrors. These long carrier lifetimes together with exceptionally high...
