The Experts below are selected from a list of 132 Experts worldwide ranked by ideXlab platform
Michael Gratzel - One of the best experts on this subject based on the ideXlab platform.
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stable and efficient organic dye Sensitized solar Cell based on ionic liquid electrolyte
Joule, 2018Co-Authors: Peng Wang, Shaik M Zakeeruddin, Lin Yang, Heng Wu, Jing Zhang, Niansheng Xu, Shu Chen, Jeandavid Decoppet, Michael GratzelAbstract:Summary Dye-Sensitized solar Cells (DSCs) for outdoor applications must show both high efficiency and long-term stability. Here we introduce a co-Sensitized, ionic liquid electrolyte-based DSC meeting these requirements. A key feature of our embodiment is the concerted action of two judiciously designed organic dyes, whose co-adsorption at the surface of a mesoscopic TiO2 scaffold results in the formation of a compact and highly robust self-assembled monolayer, harvesting sunlight across the whole visible region and converting the photons into charges with near-unity quantum efficiency. Apart from producing a high photocurrent, the dense dye layer blocks the back electron transfer from TiO2 to the redox electrolyte, increasing the photovoltage. This allows for the first time to attain a solar to electric power-conversion efficiency of 10% with an ionic liquid-based DSC. Remarkably, the co-Sensitized Cell is stable under both full-sunlight soaking at 60°C and heat stress at 85°C for 1,000 hr.
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a selective co sensitization approach to increase photon conversion efficiency and electron lifetime in dye Sensitized solar Cells
Physical Chemistry Chemical Physics, 2012Co-Authors: Loc H Nguyen, Michael Gratzel, Hemant Kumar Mulmudi, Dharani Sabba, Sneha A Kulkarni, Sudip K Batabyal, Kazuteru Nonomura, S G MhaisalkarAbstract:Ruthenium-based C106 and organic D131 sensitizers have been judicially chosen for co-sensitization due to their complementary absorption properties and different molecular sizes. Co-sensitization yields a higher light-harvesting efficiency as well as better dye coverage to passivate the surface of TiO2. The co-Sensitized devices C106 + D131 showed significant enhancement in the performance (η = 11.1%), which is a marked improvement over baseline devices Sensitized with either D131 (η = 5.6%) or C106 (η = 9.5%). The improved performance of the co-Sensitized Cell is attributed to the combined enhancement in the short circuit current, open circuit voltage, and the fill-factor of the solar Cells. Jsc is improved because of the complementary absorption spectra and favorable energy level alignments of both dyes; whereas, Voc is improved because of the better surface coverage helping to reduce the recombination and increase the electron life time. The origins of these enhancements have been systematically studied through dye desorption, absorption spectroscopy, and intensity modulated photovoltage spectroscopy investigations.
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analysis of electronic and optical losses in cu in ga se2 dye Sensitized Cell tandem solar Cells
Energy Procedia, 2010Co-Authors: S Seyrling, Michael Gratzel, Sophie Wenger, A N TiwariAbstract:Abstract To optimize dual junction solar Cells using a dye-Sensitized Cell (DSC) as top Cell and a Cu(In,Ga)Se2 (CIGS) Cell as bottom Cell, both optical and electronic loss mechanisms were investigated. The light absorption and optical losses in various layers were investigated through transmission measurements, and the amount of light available for photogeneration of charge carriers was determined. From the measured light balance, a maximum possible current for the Cells was estimated. I-V curves of stacked solar Cells were analyzed to investigate possible electronic loss mechanisms. From the results gained in these measurements, conclusions about the limiting factors and potential optimizations in DSC/CIGS tandem solar Cells could be drawn. Calculations showed that current densities up to 20 mAcm−2 can be generated in a CIGS bottom Cell with the light transmitted from the DSC. This would correspond to an efficiency exceeding 20%, given that highly transmitting DSCs yielding such high currents can be provided.
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molecular engineering of panchromatic unsymmetrical squaraines for dye Sensitized solar Cell applications
Journal of Materials Chemistry, 2010Co-Authors: Hyunbong Choi, Kihyung Song, Jaejung Ko, Md K Nazeeruddin, Michael GratzelAbstract:Three unsymmetrical squaraine dyes JK-64, JK-65, and JK-64Hx, containing a bulky spirobifluorene or hexyloxyphenyl unit are designed and synthesized. These sensitizers, when anchored onto a TiO2 surface, exhibit decreased aggregation as well as enhanced unidirectional flow of electrons. Under standard global AM 1.5 solar conditions, an optimized JK-64Hx Sensitized Cell gave a short-circuit photocurrent density (Jsc) of 12.82 mA cm−2, an open-circuit voltage (Voc) of 0.54 V and a fill factor (ff) of 0.75, corresponding to an overall conversion efficiency (η) of 5.20%.
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high molar extinction coefficient organic sensitizers for efficient dye Sensitized solar Cells
Chemistry: A European Journal, 2010Co-Authors: Hyunbong Choi, Kihyung Song, Junho Yum, Md K Nazeeruddin, Ines Raabe, Duckhyun Kim, Francesca Teocoli, Chulwoo Kim, Michael GratzelAbstract:We have designed and synthesized highly efficient organic sensitizers with a planar thienothiophene-vinylene-thienothiophene linker. Under standard global AM 1.5 solar conditions, the JK-113-Sensitized Cell gave a short circuit photocurrent density (J(sc)) of 17.61 mAcm(-2), an open-circuit voltage (V-oc) of 0.71 V, and a fill factor (FF) of 72%, corresponding to an overall conversion efficiency (eta) of 9.1%. The incident monochromatic photo-to-current conversion efficiency (IPCE) of JK-113 exceeds 80% over the spectral region from 400 to 640 nm, reaching its maximum of 93% at 475 nm. The band tails off toward 770 nm, contributing to the broad spectral light harvesting. Solar-Cell devices based oil the sensitizer JK-113 in conjunction with a volatile electrolyte and a solvent-free ionic liquid electrolyte gave high conversion efficiencies of 9.1% and 7.9%, respectively. The JK-113-based solar Cell fabricated using a solvent-free ionic liquid electrolyte showed exCellent stability under light soaking at 60 degrees C for 1000 h.
Zafar Iqbal - One of the best experts on this subject based on the ideXlab platform.
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synthesis of double d a branched organic dyes employing indole and phenoxazine as donors for efficient dsscs
Tetrahedron, 2014Co-Authors: Yanping Hong, Zafar IqbalAbstract:Abstract Four novel metal-free organic sensitizers bearing double donor–acceptor (D–A) branches with indole and phenoxazine units as donors (SDD1–4) and cyanoacrylic acid as electron acceptor were synthesized and characterized for dye-Sensitized solar Cells (DSSCs). Dyes SDD1–3 were designed with indole as a donor and 1,4-phenylenebis(methylene), 1,4-butylene and 1,6-hexylene as a linker, respectively, while the dye SDD4 was designed with phenoxazine as a core donor. Their photophysical, electrochemical, and DSSCs characteristics were investigated. The results show that the architecture structure of the linkage affects the performance of the Cells slightly. The DSSCs based on SDD4 shows much higher η than the DSSCs based on SDD1–3, which indicated that phenoxazine is a better donor than indole. Under standard global AM 1.5 solar condition (100 mW cm−2), the SDD4 dye-Sensitized Cell gave the highest η of 4.33% with chenodeoxycholic acid as a coadsorbent, reaching 82% of N719-based DSSCs.
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Synthesis of double D–A branched organic dyes employing indole and phenoxazine as donors for efficient DSSCs
Tetrahedron, 2014Co-Authors: Yanping Hong, Zafar IqbalAbstract:Abstract Four novel metal-free organic sensitizers bearing double donor–acceptor (D–A) branches with indole and phenoxazine units as donors (SDD1–4) and cyanoacrylic acid as electron acceptor were synthesized and characterized for dye-Sensitized solar Cells (DSSCs). Dyes SDD1–3 were designed with indole as a donor and 1,4-phenylenebis(methylene), 1,4-butylene and 1,6-hexylene as a linker, respectively, while the dye SDD4 was designed with phenoxazine as a core donor. Their photophysical, electrochemical, and DSSCs characteristics were investigated. The results show that the architecture structure of the linkage affects the performance of the Cells slightly. The DSSCs based on SDD4 shows much higher η than the DSSCs based on SDD1–3, which indicated that phenoxazine is a better donor than indole. Under standard global AM 1.5 solar condition (100 mW cm−2), the SDD4 dye-Sensitized Cell gave the highest η of 4.33% with chenodeoxycholic acid as a coadsorbent, reaching 82% of N719-based DSSCs.
Francoise Bontemps - One of the best experts on this subject based on the ideXlab platform.
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targeting dna repair with aphidicolin sensitizes primary chronic lymphocytic leukemia Cells to purine analogs
Oncotarget, 2016Co-Authors: Eliza Starczewska, Maxime Beyaert, Lucienne Michaux, Mariechristiane Vekemans, Pascale Saussoy, Ainhoa Arana Echarri, Caroline Smal, Eric Van Den Neste, Francoise BontempsAbstract:// Eliza Starczewska 1 , Maxime Beyaert 1 , Lucienne Michaux 2 , Marie-Christiane Vekemans 2 , Pascale Saussoy 3 , Vanesa Bol 4 , Ainhoa Arana Echarri 1 , Caroline Smal 1 , Eric Van Den Neste 1, 2 , Francoise Bontemps 1 1 de Duve Institute, Universite Catholique de Louvain, B-1200 Brussels, Belgium 2 Department of Hematology, Cliniques Universitaires Saint-Luc, Universite Catholique de Louvain, B-1200 Brussels, Belgium 3 Service de Biologie Clinique, Cliniques Universitaires Saint-Luc, Universite Catholique de Louvain, B-1200 Brussels, Belgium 4 Center for Molecular Imaging, Radiotherapy and Oncology, Institut de Recherche Experimentale et Clinique (IREC), Universite Catholique de Louvain, B-1200 Brussels, Belgium Correspondence to: Francoise Bontemps, email: francoise.bontemps@uclouvain.be Keywords: chronic lymphocytic leukemia, DNA damage, fludarabine, aphidicolin, γH2AX Received: March 09, 2016 Accepted: May 04, 2016 Published: May 20, 2016 ABSTRACT Purine analogs are among the most effective chemotherapeutic drugs for the treatment of chronic lymphocytic leukemia (CLL). However, chemoresistance and toxicity limit their clinical use. Here, we report that the DNA polymerase inhibitor aphidicolin, which displayed negligible cytotoxicity as a single agent in primary CLL Cells, markedly synergizes with fludarabine and cladribine via enhanced apoptosis. Importantly, synergy was recorded regardless of CLL prognostic markers. At the molecular level, aphidicolin enhanced purine analog-induced phosphorylation of p53 and accumulation of γH2AX, consistent with increase in DNA damage. In addition, aphidicolin delayed γH2AX disappearance that arises after removal of purine analogs, suggesting that aphidicolin causes an increase in DNA damage by impeding DNA damage repair. Similarly, aphidicolin inhibited UV-induced DNA repair known to occur primarily through the nucleotide excision repair (NER) pathway. Finally, we showed that fludarabine induced nuclear import of XPA, an indispensable factor for NER, and that XPA silencing Sensitized Cell lines to undergo apoptosis in response to fludarabine. Together, our data indicate that aphidicolin potentiates the cytotoxicity of purine analogs by inhibiting a DNA repair pathway that involves DNA polymerases, most likely NER, and provide a rationale for manipulating it to therapeutic advantage.
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targeting dna repair with aphidicolin sensitizes primary chronic lymphocytic leukemia Cells to purine analogs
Oncotarget, 2016Co-Authors: Eliza Starczewska, Maxime Beyaert, Lucienne Michaux, Mariechristiane Vekemans, Pascale Saussoy, Ainhoa Arana Echarri, Caroline Smal, Eric Van Den Neste, Francoise BontempsAbstract:// Eliza Starczewska 1 , Maxime Beyaert 1 , Lucienne Michaux 2 , Marie-Christiane Vekemans 2 , Pascale Saussoy 3 , Vanesa Bol 4 , Ainhoa Arana Echarri 1 , Caroline Smal 1 , Eric Van Den Neste 1, 2 , Francoise Bontemps 1 1 de Duve Institute, Universite Catholique de Louvain, B-1200 Brussels, Belgium 2 Department of Hematology, Cliniques Universitaires Saint-Luc, Universite Catholique de Louvain, B-1200 Brussels, Belgium 3 Service de Biologie Clinique, Cliniques Universitaires Saint-Luc, Universite Catholique de Louvain, B-1200 Brussels, Belgium 4 Center for Molecular Imaging, Radiotherapy and Oncology, Institut de Recherche Experimentale et Clinique (IREC), Universite Catholique de Louvain, B-1200 Brussels, Belgium Correspondence to: Francoise Bontemps, email: francoise.bontemps@uclouvain.be Keywords: chronic lymphocytic leukemia, DNA damage, fludarabine, aphidicolin, γH2AX Received: March 09, 2016 Accepted: May 04, 2016 Published: May 20, 2016 ABSTRACT Purine analogs are among the most effective chemotherapeutic drugs for the treatment of chronic lymphocytic leukemia (CLL). However, chemoresistance and toxicity limit their clinical use. Here, we report that the DNA polymerase inhibitor aphidicolin, which displayed negligible cytotoxicity as a single agent in primary CLL Cells, markedly synergizes with fludarabine and cladribine via enhanced apoptosis. Importantly, synergy was recorded regardless of CLL prognostic markers. At the molecular level, aphidicolin enhanced purine analog-induced phosphorylation of p53 and accumulation of γH2AX, consistent with increase in DNA damage. In addition, aphidicolin delayed γH2AX disappearance that arises after removal of purine analogs, suggesting that aphidicolin causes an increase in DNA damage by impeding DNA damage repair. Similarly, aphidicolin inhibited UV-induced DNA repair known to occur primarily through the nucleotide excision repair (NER) pathway. Finally, we showed that fludarabine induced nuclear import of XPA, an indispensable factor for NER, and that XPA silencing Sensitized Cell lines to undergo apoptosis in response to fludarabine. Together, our data indicate that aphidicolin potentiates the cytotoxicity of purine analogs by inhibiting a DNA repair pathway that involves DNA polymerases, most likely NER, and provide a rationale for manipulating it to therapeutic advantage.
A N Tiwari - One of the best experts on this subject based on the ideXlab platform.
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analysis of electronic and optical losses in cu in ga se2 dye Sensitized Cell tandem solar Cells
Energy Procedia, 2010Co-Authors: S Seyrling, Michael Gratzel, Sophie Wenger, A N TiwariAbstract:Abstract To optimize dual junction solar Cells using a dye-Sensitized Cell (DSC) as top Cell and a Cu(In,Ga)Se2 (CIGS) Cell as bottom Cell, both optical and electronic loss mechanisms were investigated. The light absorption and optical losses in various layers were investigated through transmission measurements, and the amount of light available for photogeneration of charge carriers was determined. From the measured light balance, a maximum possible current for the Cells was estimated. I-V curves of stacked solar Cells were analyzed to investigate possible electronic loss mechanisms. From the results gained in these measurements, conclusions about the limiting factors and potential optimizations in DSC/CIGS tandem solar Cells could be drawn. Calculations showed that current densities up to 20 mAcm−2 can be generated in a CIGS bottom Cell with the light transmitted from the DSC. This would correspond to an efficiency exceeding 20%, given that highly transmitting DSCs yielding such high currents can be provided.
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fabrication and performance of a monolithic dye Sensitized tio2 cu in ga se2 thin film tandem solar Cell
Applied Physics Letters, 2009Co-Authors: Sophie Wenger, S Seyrling, A N Tiwari, Michael GratzelAbstract:Tandem solar Cells using different bandgap absorbers allow efficient photovoltaic conversion in a wide range of the solar spectrum. The optical gaps of the dye-Sensitized solar Cell and the Cu(In,Ga)Se2 solar Cell are ideal for application in double-junction devices and a mechanically stacked device has been reported recently. We report on the monolithic integration of these subCells to cut optical losses at needless interfaces and material costs, achieving 12.2% conversion efficiency at full sunlight. The high open-circuit voltage confirms the series connection, but corrosion of the Cu(In,Ga)Se2 Cell by the redox mediator (I−/I3− couple) of the dye-Sensitized Cell and an associated voltage loss ( 140 mV) limits performance.
Peidong Yang - One of the best experts on this subject based on the ideXlab platform.
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nanowire dye Sensitized solar Cells
Nature Materials, 2005Co-Authors: Matt Law, Lori E Greene, Justin C Johnson, Richard J Saykally, Peidong YangAbstract:Excitonic solar Cells1—including organic, hybrid organic–inorganic and dye-Sensitized Cells (DSCs)—are promising devices for inexpensive, large-scale solar energy conversion. The DSC is currently the most efficient2 and stable3 excitonic photoCell. Central to this device is a thick nanoparticle film that provides a large surface area for the adsorption of light-harvesting molecules. However, nanoparticle DSCs rely on trap-limited diffusion for electron transport, a slow mechanism that can limit device efficiency, especially at longer wavelengths. Here we introduce a version of the dye-Sensitized Cell in which the traditional nanoparticle film is replaced by a dense array of oriented, crystalline ZnO nanowires. The nanowire anode is synthesized by mild aqueous chemistry and features a surface area up to one-fifth as large as a nanoparticle Cell. The direct electrical pathways provided by the nanowires ensure the rapid collection of carriers generated throughout the device, and a full Sun efficiency of 1.5% is demonstrated, limited primarily by the surface area of the nanowire array.
