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Anders Hagfeldt - One of the best experts on this subject based on the ideXlab platform.
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efficient Dye regeneration at low driving force achieved in triphenylamine Dye leg4 and tempo redox mediator based Dye sensitized solar cells
Physical Chemistry Chemical Physics, 2015Co-Authors: Wenxing Yang, Anders Hagfeldt, Nick Vlachopoulos, Yan Hao, Gerrit BoschlooAbstract:Minimizing the driving force required for the regeneration of Oxidized Dyes using redox mediators in an electrolyte is essential to further improve the open-circuit voltage and efficiency of Dye-sensitized solar cells (DSSCs). Appropriate combinations of redox mediators and Dye molecules should be explored to achieve this goal. Herein, we present a triphenylamine Dye, LEG4, in combination with a TEMPO-based electrolyte in acetonitrile (E0 = 0.89 V vs. NHE), reaching an efficiency of up to 5.4% under one sun illumination and 40% performance improvement compared to the previously and widely used indoline Dye D149. The origin of this improvement was found to be the increased Dye regeneration efficiency of LEG4 using the TEMPO redox mediator, which regenerated more than 80% of the Oxidized Dye with a driving force of only ∼0.2 eV. Detailed mechanistic studies further revealed that in addition to electron recombination to Oxidized Dyes, recombination of electrons from the conducting substrate and the mesoporous TiO2 film to the TEMPO+ redox species in the electrolyte accounts for the reduced short circuit current, compared to the state-of-the-art cobalt tris(bipyridine) electrolyte system. The diffusion length of the TEMPO-electrolyte based DSSCs was determined to be ∼0.5 μm, which is smaller than the ∼2.8 μm found for cobalt-electrolyte based DSSCs. These results show the advantages of using LEG4 as a sensitizer, compared to previously record indoline Dyes, in combination with a TEMPO-based electrolyte. The low driving force for efficient Dye regeneration presented by these results shows the potential to further improve the power conversion efficiency (PCE) of DSSCs by utilizing redox couples and Dyes with a minimal need of driving force for high regeneration yields.
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combining a small hole conductor molecule for efficient Dye regeneration and a hole conducting polymer in a solid state Dye sensitized solar cell
Journal of Physical Chemistry C, 2012Co-Authors: Erik M. J. Johansson, Gerrit Boschloo, Licheng Sun, Lei Yang, Erik O Gabrielsson, Peter W Lohse, Anders HagfeldtAbstract:In Dye-sensitized solar cells (DSC) an efficient transfer of dioles from the Oxidized Dye to the contact is necessary, which in solid-state DSC is performed by hole-conductor molecules. In this rep ...
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combining a small hole conductor molecule for efficient Dye regeneration and a hole conducting polymer in a solid state Dye sensitized solar cell
Journal of Physical Chemistry C, 2012Co-Authors: Erik M. J. Johansson, Gerrit Boschloo, Lei Yang, Erik O Gabrielsson, Peter W Lohse, Anders HagfeldtAbstract:In Dye-sensitized solar cells (DSC) an efficient transfer of holes from the Oxidized Dye to the contact is necessary, which in solid-state DSC is performed by hole-conductor molecules. In this report we use photoinduced absorption and transient absorption spectroscopy to show that a small hole-conducting molecule, tris(p-anisyl)amine, regenerates Dye molecules in the pores of the Dye-sensitized TiO2 nanoparticle electrode efficiently even for thick (>5 μm) electrodes. For similar thicknesses we observe incomplete regeneration using a larger polymer hole-conductor. However, the performance of the solar cells with the small hole-conductor molecules is poor due to that inefficient hole conduction in these small molecules may limit the collection of the charges at the contacts. Polymer hole-conductors, which may have a good hole conductivity, also have a high molecular weight, which makes these polymers difficult to infiltrate into the smallest pores in the electrode. We show that a conducting polymer, P3HT, ...
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characteristics of the iodide triiodide redox mediator in Dye sensitized solar cells
Accounts of Chemical Research, 2009Co-Authors: Gerrit Boschloo, Anders HagfeldtAbstract:Dye-sensitized solar cells (DSCs) have gained widespread interest because of their potential for low-cost solar energy conversion. Currently, the certified record efficiency of these solar cells is 11.1%, and measurements of their durability and stability suggest lifetimes exceeding 10 years under operational conditions. The DSC is a photoelectrochemical system: a monolayer of sensitizing Dye is adsorbed onto a mesoporous TiO2 electrode, and the electrode is sandwiched together with a counter electrode. An electrolyte containing a redox couple fills the gap between the electrodes. The redox couple is a key component of the DSC. The reduced part of the couple regenerates the photo-Oxidized Dye. The formed Oxidized species diffuses to the counter electrode, where it is reduced. The photovoltage of the device depends on the redox couple because it sets the electrochemical potential at the counter electrode. The redox couple also affects the electrochemical potential of the TiO2 electrode through the recombin...
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photoinduced absorption spectroscopy as a tool in the study of Dye sensitized solar cells
Inorganica Chimica Acta, 2008Co-Authors: Gerrit Boschloo, Anders HagfeldtAbstract:Photoinduced absorption (PIA) spectroscopy, where the excitation is provided by a square-wave modulated (on/off) monochromatic light source, is a versatile tool in the study of Dye-sensitized solar cells. Spectra of transient species, such as the Oxidized Dye, can easily be obtained and their kinetics can be explored using frequency or time-resolved techniques. Experimental PIA conditions can be kept close to typical solar cell operating conditions, allowing extraction of relevant time constants. PIA is also a suitable method to study the quality of pore filling in case of solid hole conductors. Dye molecules that are not in direct contact with the hole conductor will have long lifetimes in their Oxidized state and appear clearly in the PIA spectrum. The basic principles of PIA are explained using the example of electron injection and recombination in Dye-sensitized TiO2 in the absence of redox electrolyte.
Hashem, Dalal A - One of the best experts on this subject based on the ideXlab platform.
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تأثير إضاÙ�Ø© طبقات نانوية على أداء الخلايا الشمسية المØÙ�زة باستخدام إيوسين (Y) ومشتقاته
الجامعة الإسلامية - غزة, 2017Co-Authors: Hashem, Dalal AAbstract:Dye sensitized solar cells (DSSCs) is a new technology which considered to be the third generation of the photovoltaic technology. DSSCs have multiple advantages such as simple fabrication, low-cost and environment friendly. Even though the multiple advantages of the DSSCs, the efficiency of the DSSCs still limited due to the complexity of the device. That’s why DSSC technology is considered to be a preferable research field in which many studies are being conducted to increase the efficiency of the device. The objectives of this thesis are to prepare Dye sensitized solar cells (DSSCs) using titanium dioxide (TiO2) as a semiconducting layer based on eosin Y Dye with adding some modifications to the structure of the device. These modifications include changing the Dyeing duration of TiO2 films, preparing a derivative of eosin Y solution acting as a new photosensitizer, changing the pH of the Dye solution and adding ZnO blocking layers. The results showed that Dyeing the TiO2 films for 3 hours can lead to a better performance of the assembled DSSC. In addition, a derivative of eosin Y was prepared by adding phenylhydrazine hydrochloride solution to the eosin Y solution in a molar ration 1:1 which contributed in enhancing the efficiency of the assembled DSSC. The treatment of the Dye solutions with phosphoric acid resulted in better performance in comparison with hydrochloric acid and nitric acid treatment. The mechanism used in suppressing the recombination of injected electrons with both the redox electrolyte and the Oxidized Dye is adding ZnO blocking upper-layers which act as a barrier. By adding the ZnO upper layers, the performance of the DSSC was improved.تÙ�عتبر الخلايا الشمسية الصبغية تكنولوجيا جديدة Ùˆ تÙ�صنَّÙ� بأنها الجيل الثالث Ù�ÙŠ تكنولوجيا الخلايا الشمسية. للخلايا الشمسية الصبغية مزايا عÙ�دَّة منها بساطة تصنيعها، وتكلÙ�تها المنخÙ�ضة، كما أنها تÙ�عتبر صديقة للبيئة. ولكن على الرغم من هذه المزايا إلَّا أنَّ ÙƒÙ�اءة الخلايا الشمسية الصبغية لاتزال Ù…Øدودة، وذلك بسبب تعقيد بناء هذه الخلايا. هذا السبب قد جعل البØØ« Ù�ÙŠ الخلايا الشمسية الصبغية مجالاً خصباً ومÙ�ضلاً Øيث تÙ�بذل Ù�يه الكثير من الدراسات والتي تسعى جميعها لزيادة ÙƒÙ�اءة الخلايا الشمسية الصبغية. إن أهداÙ� هذا البØØ« هي تصنيع خلايا شمسية صبغية باستخدام ثاني أكسيد التيتانيوم (TiO2) كطبقة شبه موصلة معتمدةً على صبغة إيوسين (Y)ØŒ مع إضاÙ�Ø© بعض التØسينات إلى بÙ�نية هذه الخلايا. هذه التØسينات تشمل تغيير مدة صبغ Ø£Ù�لام (TiO2)ØŒ وتØضير صبغة Ù…Ù�شتقة من Ù…Øلول صبغة الإيوسين (Y) والتي تعمل كمØÙ�ًّز ضوئي جديد، إلى جانب تغيير درجة Øامضية (pH) Ù…Øلول الصبغة المÙ�ستخدم، Ùˆ إضاÙ�Ø© طبقات من أكسيد الزنك (ZnO) والتي تعمل كطبقة عازلة Ù�ÙŠ الخلايا الشمسية الصبغية. وتظهر النتائج أنَّ صبغ Ø£Ù�لام (TiO2) لمدة ثلاث ساعات يساهم Ù�ÙŠ تØسين أداء الخلايا الشمسية الصبغية، كما أنَّ الصبغة المÙ�شتقة من إيوسين (Y) والتي تمَّ تØضيرها من خلال إضاÙ�Ø© Ù…Øلول هيدروكلوريك Ù�ينيل هيدرازين إلى Ù…Øلول الإيوسين (Y) بنسبة مولية 1:1 قد أدى إلى زيادة ÙƒÙ�اءة الخلايا الشمسية الصبغية. بالإضاÙ�Ø© إلى ما سبق، Ù�إنَّ معالجة Ù…Øاليل الصبغة بØمض الÙ�وسÙ�وريك قد أعطى أداء اÙ�ضل Ù�ÙŠ الخلايا الشمسية الصبغية مقارنة بمعالجة Ù…Øلول الصبغة بكلÙ� من Øمض الهيدروكلوريك ÙˆØمض النيتريك. إنَّ الآلية المتَّبعة لمنع إعادة ارتباط الإلكترونات مع كلّÙ� من سائل الالكترولايت Ùˆ الصبغة المتأكسدة هي إضاÙ�Ø© طبقات عازلة عÙ�ليا من أكسيد الزنك (ZnO) والتي تعمل ÙƒØاجز. Øيث تØسن أداء الخلايا الشمسية الصبغية بشكل جيد عند إضاÙ�Ø© تلك الطبقات العليا من أكسيد الزنك
Francesco Buda - One of the best experts on this subject based on the ideXlab platform.
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photocatalytic water splitting cycle in a Dye catalyst supramolecular complex ab initio molecular dynamics simulations
The Journal of Physical Chemistry, 2019Co-Authors: Yang Shao, Jessica M De Ruiter, Huub J M De Groot, Francesco BudaAbstract:A Dye-sensitized photoelectrochemical cell (DS-PEC) is a promising device for direct conversion of solar energy into fuel. The basic idea, inspired by natural photosynthesis, is to couple the photoinduced charge separation process to catalytic water splitting. The photo-Oxidized Dye coupled to a water oxidation catalyst (WOC) should exert a thermodynamic driving force for the catalytic cycle, while water provides the electrons for regenerating the Oxidized Dye. These conditions impose specific energetic constraints on the molecular components of the photoanode in the DS-PEC. Here, we consider a supramolecular complex integrating a mononuclear Ru-based WOC with a fully organic naphthalene-diimide (NDI) Dye that is able to perform fast photoinduced electron injection into the conduction band of the titanium-dioxide semiconductor anode. By means of constrained ab initio molecular dynamics simulations in explicit water solvent, it is shown that the Oxidized NDI provides enough driving force for the whole photocatalytic water splitting cycle. The results provide strong evidence for the significant role of spin alignment and solvent rearrangement in facilitating the proton-coupled electron transfer processes. The predicted activation free energy barriers confirm that the O–O bond formation is the rate-limiting step. Our results expand the current understanding of the photocatalytic water oxidation mechanism and provide guidelines for the optimization of high-performance DS-PEC devices.
Gerrit Boschloo - One of the best experts on this subject based on the ideXlab platform.
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effect of coordination sphere geometry of copper redox mediators on regeneration and recombination behavior in Dye sensitized solar cell applications
ACS Applied Energy Materials, 2018Co-Authors: Yasemin Saygili, Fabrizio Giordano, Shaik M Zakeeruddin, Michele Pavone, Marko Stojanovic, Hannes Michaels, Jan Tiepelt, Joel Teuscher, Arianna Massaro, Gerrit BoschlooAbstract:The recombination of injected electrons with Oxidized redox species and regeneration behavior of copper redox mediators are investigated for four copper complexes, [Cu(dmby)2]2+/1+ (dmby = 6,6′-dimethyl-2,2′-bipyridine), [Cu(tmby)2]2+/1+ (tmby = 4,4′,6,6′- tetramethyl-2,2′-bipyridine), [Cu(eto)2]2+/1+ (eto = 4-ethoxy-6,6′-dimethyl-2,2′-bipyridine), and [Cu(dmp)2]2+/1+ (dmp = bis(2,9-dimethyl-1,10-phenantroline). These complexes were examined in conjunction with the D5, D35, and D45 sensitizers, having various degrees of blocking moieties. The experimental results were further supported by density functional theory calculations, showing that the low reorganization energies, λ, of tetra-coordinated Cu(I) species (λ = 0.31–0.34 eV) allow efficient regeneration of the Oxidized Dye at driving forces down to approximately 0.1 eV. The regeneration electron transfer reaction is in the Marcus normal regime. However, for Cu(II) species, the presence of 4-tert-butylpyridine (TBP) in electrolyte medium results in pen...
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copper bipyridyl redox mediators for Dye sensitized solar cells with high photovoltage
Journal of the American Chemical Society, 2016Co-Authors: Yasemin Saygili, Magnus Soderberg, Norman Pellet, Fabrizio Giordano, Yiming Cao, Ana B Munozgarcia, Shaik M Zakeeruddin, Nick Vlachopoulos, Michele Pavone, Gerrit BoschlooAbstract:Redox mediators play a major role determining the photocurrent and the photovoltage in Dye-sensitized solar cells (DSCs). To maintain the photocurrent, the reduction of Oxidized Dye by the redox mediator should be significantly faster than the electron back transfer between TiO2 and the Oxidized Dye. The driving force for Dye regeneration with the redox mediator should be sufficiently low to provide high photovoltages. With the introduction of our new copper complexes as promising redox mediators in DSCs both criteria are satisfied to enhance power conversion efficiencies. In this study, two copper bipyridyl complexes, Cu(II/I)(dmby)2TFSI2/1 (0.97 V vs SHE, dmby = 6,6′-dimethyl-2,2′-bipyridine) and Cu(II/I)(tmby)2TFSI2/1 (0.87 V vs SHE, tmby = 4,4′,6,6′-tetramethyl-2,2′-bipyridine), are presented as new redox couples for DSCs. They are compared to previously reported Cu(II/I)(dmp)2TFSI2/1 (0.93 V vs SHE, dmp = bis(2,9-dimethyl-1,10-phenanthroline). Due to the small reorganization energy between Cu(I) and ...
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efficient Dye regeneration at low driving force achieved in triphenylamine Dye leg4 and tempo redox mediator based Dye sensitized solar cells
Physical Chemistry Chemical Physics, 2015Co-Authors: Wenxing Yang, Anders Hagfeldt, Nick Vlachopoulos, Yan Hao, Gerrit BoschlooAbstract:Minimizing the driving force required for the regeneration of Oxidized Dyes using redox mediators in an electrolyte is essential to further improve the open-circuit voltage and efficiency of Dye-sensitized solar cells (DSSCs). Appropriate combinations of redox mediators and Dye molecules should be explored to achieve this goal. Herein, we present a triphenylamine Dye, LEG4, in combination with a TEMPO-based electrolyte in acetonitrile (E0 = 0.89 V vs. NHE), reaching an efficiency of up to 5.4% under one sun illumination and 40% performance improvement compared to the previously and widely used indoline Dye D149. The origin of this improvement was found to be the increased Dye regeneration efficiency of LEG4 using the TEMPO redox mediator, which regenerated more than 80% of the Oxidized Dye with a driving force of only ∼0.2 eV. Detailed mechanistic studies further revealed that in addition to electron recombination to Oxidized Dyes, recombination of electrons from the conducting substrate and the mesoporous TiO2 film to the TEMPO+ redox species in the electrolyte accounts for the reduced short circuit current, compared to the state-of-the-art cobalt tris(bipyridine) electrolyte system. The diffusion length of the TEMPO-electrolyte based DSSCs was determined to be ∼0.5 μm, which is smaller than the ∼2.8 μm found for cobalt-electrolyte based DSSCs. These results show the advantages of using LEG4 as a sensitizer, compared to previously record indoline Dyes, in combination with a TEMPO-based electrolyte. The low driving force for efficient Dye regeneration presented by these results shows the potential to further improve the power conversion efficiency (PCE) of DSSCs by utilizing redox couples and Dyes with a minimal need of driving force for high regeneration yields.
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combining a small hole conductor molecule for efficient Dye regeneration and a hole conducting polymer in a solid state Dye sensitized solar cell
Journal of Physical Chemistry C, 2012Co-Authors: Erik M. J. Johansson, Gerrit Boschloo, Licheng Sun, Lei Yang, Erik O Gabrielsson, Peter W Lohse, Anders HagfeldtAbstract:In Dye-sensitized solar cells (DSC) an efficient transfer of dioles from the Oxidized Dye to the contact is necessary, which in solid-state DSC is performed by hole-conductor molecules. In this rep ...
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combining a small hole conductor molecule for efficient Dye regeneration and a hole conducting polymer in a solid state Dye sensitized solar cell
Journal of Physical Chemistry C, 2012Co-Authors: Erik M. J. Johansson, Gerrit Boschloo, Lei Yang, Erik O Gabrielsson, Peter W Lohse, Anders HagfeldtAbstract:In Dye-sensitized solar cells (DSC) an efficient transfer of holes from the Oxidized Dye to the contact is necessary, which in solid-state DSC is performed by hole-conductor molecules. In this report we use photoinduced absorption and transient absorption spectroscopy to show that a small hole-conducting molecule, tris(p-anisyl)amine, regenerates Dye molecules in the pores of the Dye-sensitized TiO2 nanoparticle electrode efficiently even for thick (>5 μm) electrodes. For similar thicknesses we observe incomplete regeneration using a larger polymer hole-conductor. However, the performance of the solar cells with the small hole-conductor molecules is poor due to that inefficient hole conduction in these small molecules may limit the collection of the charges at the contacts. Polymer hole-conductors, which may have a good hole conductivity, also have a high molecular weight, which makes these polymers difficult to infiltrate into the smallest pores in the electrode. We show that a conducting polymer, P3HT, ...
M Tachiya - One of the best experts on this subject based on the ideXlab platform.
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lithium ion effect on electron injection from a photoexcited coumarin derivative into a tio2 nanocrystalline film investigated by visible to ir ultrafast spectroscopy
Journal of Physical Chemistry B, 2005Co-Authors: Akihiro Furube, Ryuzi Katoh, Kohjiro Hara, Tadatake Sato, Shigeo Murata, Hironori Arakawa, M TachiyaAbstract:The dynamics of ultrafast electron injection from a coumarin derivative (NKX-2311), which is an efficient photosensitizer for Dye-sensitized solar cells, into the conduction band of TiO2 nanocrystalline films have been investigated by means of femtosecond transient absorption spectroscopy in a wide wavelength range from 600 nm to 10 μm. In the absence of Li+ ions, electron injection into the TiO2 conduction band occurred in about 300 fs. In the presence of Li+ ions, however, electron injection occurred within ∼100 fs, and the Oxidized Dye generated was found to interact with nearby Li+ ions. Possible positions of Li+ ion attachment to the Dye molecule were examined by means of semiempirical molecular orbital calculations. The electron injection efficiency was found to increase by a factor of 1.37 in the presence of Li+ ions. The effects of Li+ ions on the energy of the TiO2 conduction band and the electronic interaction between the Dye molecule and Li+ ions are discussed, and the major cause for the accel...
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ultrafast direct and indirect electron injection processes in a photoexcited Dye sensitized nanocrystalline zinc oxide film the importance of exciplex intermediates at the surface
Journal of Physical Chemistry B, 2004Co-Authors: Akihiro Furube, Ryuzi Katoh, Kohjiro Hara, Shigeo Murata, Hironori Arakawa, Toshitada Yoshihara, M TachiyaAbstract:The processes involved in ultrafast electron injection from a photoexcited novel coumarin Dye (NKX-2311), an efficient photosensitizer for TiO2-based Dye-sensitized solar cells, into the conduction band of a nanocrystalline ZnO film were investigated by observing the femtosecond transient absorption in the visible-to-infrared range (600−5000 nm). After photoexcitation of adsorbed NKX-2311 Dye, the stimulated emission and absorption of the singlet excited Dye decayed with a 500-fs time constant. These were followed by rises in absorptions of the Oxidized Dye and conduction-band electrons, indicating a direct electron-injection process. In addition, indirect electron-injection processes involving intermediates were identified. The intermediates showed stimulated emission at longer wavelengths than that of the excited Dye; very broad absorptions in the near-IR region (900−1300 nm) were observed immediately after excitation, and they decayed with 1- and 10-ps time constants, leading to further rises in the ab...
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mechanism of molecular control of recombination dynamics in Dye sensitized nanocrystalline semiconductor films
Journal of Physical Chemistry B, 2004Co-Authors: Alexander V Barzykin, M TachiyaAbstract:Recent experiments have shown that it is possible to switch between electron transport limited and interfacial electron transfer (IET) limited recombination dynamics of photoinjected electrons and the Oxidized Dye molecules anchored to the TiO2 under the same spectroscopic conditions, by appropriate design of the Dye. The kinetics not only is slower in the IET limited case but also single exponential, in contrast to the highly dispersive transport limited recombination kinetics. We suggest that exponential kinetics could be a result of the Coulomb trap effect. Once an electron reaches the cation, electrostatic interaction keeps it near the cation until recombination takes place. Otherwise, dispersive transport would not allow for the exponential kinetics to develop. An analytical expression for the cation survival probability is derived that shows very good agreement with available experimental data. Physically, the Coulomb trap effect is justifiable if the relative dielectric constant of the surrounding ...
