121 results on '"Natalie Banerji"'
Search Results
52. Salt-induced thermochromism of a conjugated polyelectrolyte
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Laurent Vannay, Mario Leclerc, Yauhen Sheima, Clémence Corminboeuf, Lisa Peterhans, Natalie Banerji, Elisa Alloa, and Sophia C. Hayes
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Materials science ,Resonance Raman spectroscopy ,General Physics and Astronomy ,transient absorption ,02 engineering and technology ,010402 general chemistry ,Photochemistry ,01 natural sciences ,chemistry.chemical_compound ,resonance Raman spectroscopy ,Phase (matter) ,540 Chemistry ,Physical and Theoretical Chemistry ,chemistry.chemical_classification ,Thermochromism ,Intermolecular force ,cationic polythiophene ,Polymer ,021001 nanoscience & nanotechnology ,Polyelectrolyte ,0104 chemical sciences ,chemistry ,Polythiophene ,Absorption (chemistry) ,thermochromism ,0210 nano-technology - Abstract
We report here the photophysical properties of a water-soluble conjugated polythiophene with cationic side-chains. When dissolved in aqueous buffer solution (PBS, phosphate buffered saline), there is ordering of the polymer chains due to the presence of the salts, in contrast to pure water, where a random-coil conformation is adopted at room temperature. The ordering leads to a pronounced colour change of the solution (the absorption maximum shifts from 400 nm to 525 nm). Combining resonance Raman spectroscopy with density functional theory computations, we show a significant backbone planarization in the ordered phase. Moreover, the ratio of ordered phase to random-coil phase in PBS solution, as well as the extent of intermolecular interactions in the ordered phase, can be tuned by varying the temperature. Femtosecond transient absorption spectroscopy reveals that the excited- state behaviour of the polyelectrolyte is strongly affected by the degree of ordering. While triplet state formation is favoured in the random-coil chains, the ordered chains show a weak yield of polarons, related to interchain interactions. The investigated polyelectrolyte has been previously used as a biological DNA sensor, based on optical transduction when the conformation of the polyelectrolyte changes during assembly with the biomolecule. Therefore, our results, by correlating the photophysical properties of the polyelectrolyte to backbone and intermolecular conformation in a biologically relevant buffer, provide a significant step forward in understanding the mechanism of the biological sensing.
- Published
- 2018
53. Origin of the Enhanced Photoluminescence Quantum Yield in MAPbBr 3 Perovskite with Reduced Crystal Size
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Natalie Banerji, Giulia Longo, Henk J. Bolink, Nikolaos Droseros, Jan C. Brauer, and Michele Sessolo
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Photoluminescence ,Materials science ,530 Physics ,Exciton ,F100 ,Population ,F200 ,Energy Engineering and Power Technology ,Quantum yield ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,Condensed Matter::Materials Science ,Effective mass (solid-state physics) ,540 Chemistry ,Materials Chemistry ,Thin film ,education ,education.field_of_study ,Renewable Energy, Sustainability and the Environment ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Fuel Technology ,Chemistry (miscellaneous) ,Quantum dot ,Chemical physics ,Crystallite ,0210 nano-technology - Abstract
Methylammonium lead bromide perovskite (MAPbBr3) has been widely investigated for applications in visible perovskite light-emitting diodes (LEDs). Fine-tuning of the morphology and of the crystal size, from the microscale down to the quantum confinement regime, has been used to increase the photoluminescence quantum yield (PLQY). However, the physical processes underlying the PL emission of this perovskite remain unclear. Here, we elucidate the origin of the PL emission of polycrystalline MAPbBr3 thin films by different spectroscopic techniques. We estimate the exciton binding energy, the reduced exciton effective mass, and the trap density. Moreover, we confirm the coexistence of free carriers and excitons, quantifying their relative population and mutual interaction over a broad range of excitation densities. Finally, the enhanced PLQY upon crystal size reduction to the micro- and nanometer scale in the presence of additives is attributed to favored excitonic recombination together with reduced surface trapping thanks to efficient passivation by the additives.
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- 2018
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54. Charge migration and charge transfer in molecular systems
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Peter M. Kraus, Ursula Keller, Andrea Cannizzo, Akshaya K. Das, Oliver S. Wenger, Christopher Arrell, Jeroen A. van Bokhoven, Hans Jakob Wörner, Christopher J. Milne, Grigory Smolentsev, Joël Teuscher, Ursula Rothlisberger, Jacques-E. Moser, Matteo Lucchini, Majed Chergui, Peter Hamm, Markus Meuwly, Natalie Banerji, Pablo López-Tarifa, Elisa Liberatore, and University of Zurich
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10120 Department of Chemistry ,3104 Condensed Matter Physics ,Field (physics) ,530 Physics ,Quantum dynamics ,Attosecond ,1607 Spectroscopy ,Reviews ,Electron ,010402 general chemistry ,Dye-sensitized solar cells ,01 natural sciences ,Swiss National Center of Competence in Research: Molecular Ultrafast Science and Technology ,Radiation ,Instrumentation ,Condensed Matter Physics ,Spectroscopy ,Charge transfer dynamics ,Ionization ,0103 physical sciences ,540 Chemistry ,lcsh:QD901-999 ,Molecule ,010306 general physics ,Physics ,3105 Instrumentation ,Charge (physics) ,Charge migration ,Attosecond spectroscopy ,620 Engineering ,0104 chemical sciences ,3108 Radiation ,Chemical physics ,Temporal resolution ,570 Life sciences ,biology ,lcsh:Crystallography ,Ultrafast spectroscopy - Abstract
The transfer of charge at the molecular level plays a fundamental role in many areas of chemistry, physics, biology and materials science. Today, more than 60 years after the seminal work of R. A. Marcus, charge transfer is still a very active field of research. An important recent impetus comes from the ability to resolve ever faster temporal events, down to the attosecond time scale. Such a high temporal resolution now offers the possibility to unravel the most elementary quantum dynamics of both electrons and nuclei that participate in the complex process of charge transfer. This review covers recent research that addresses the following questions. Can we reconstruct the migration of charge across a molecule on the atomic length and electronic time scales? Can we use strong laser fields to control charge migration? Can we temporally resolve and understand intramolecular charge transfer in dissociative ionization of small molecules, in transition-metal complexes and in conjugated polymers? Can we tailor molecular systems towards specific charge-transfer processes? What are the time scales of the elementary steps of charge transfer in liquids and nanoparticles? Important new insights into each of these topics, obtained from state-of-the-art ultrafast spectroscopy and/or theoretical methods, are summarized in this review., Structural Dynamics, 4 (6), ISSN:2329-7778
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- 2017
55. Charge Transfer Dynamics from Organometal Halide Perovskite to Polymeric Hole Transport Materials in Hybrid Solar Cells
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Jan C. Brauer, Mohammad Khaja Nazeeruddin, Yong Hui Lee, and Natalie Banerji
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Materials science ,Inorganic chemistry ,Halide ,Charge (physics) ,Hybrid solar cell ,Orders of magnitude (numbers) ,law.invention ,law ,Chemical physics ,Picosecond ,Solar cell ,General Materials Science ,Physical and Theoretical Chemistry ,Perovskite (structure) - Abstract
Organometal halide perovskites have emerged as promising next-generation solar cell technologies presenting outstanding efficiencies. However, many questions concerning their working principles remain to be answered. Here, we present a detailed study of hole transfer dynamics into polymeric hole transporting materials (HTMs), poly(triarylamine) (PTAA), poly(3-hexylthiophee-2,5-diyl (P3HT), and poly[2,6-(4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b']dithiophene)-alt-4,7-(2,1,3-benzothiadiazole) (PCPDTBT). The hole transfer dynamics are shown to occur on a time scale of thousands of picoseconds, being orders of magnitude slower compared to hole transfer involving commonly used Spiro-OMeTAD as HTM.
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- 2015
56. A Close Look at Charge Generation in Polymer:Fullerene Blends with Microstructure Control
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Ester Buchaca-Domingo, Martin Heeney, Natalie Stingelin, Jelissa De Jonghe-Risse, Mariateresa Scarongella, Natalie Banerji, Martina Causa, Zhuping Fei, and Jacques-E. Moser
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Models, Molecular ,Fullerene ,Polymers ,Surface Properties ,Exciton ,Molecular Conformation ,Analytical chemistry ,Electrons ,Thiophenes ,02 engineering and technology ,Electron ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Catalysis ,symbols.namesake ,Colloid and Surface Chemistry ,Phase (matter) ,Ultrafast laser spectroscopy ,Physics::Chemical Physics ,Spectroscopy ,chemistry.chemical_classification ,Chemistry ,General Chemistry ,Polymer ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,3. Good health ,Absorption, Physicochemical ,Stark effect ,Chemical physics ,symbols ,Fullerenes ,0210 nano-technology - Abstract
We reveal some of the key mechanisms during charge generation in polymer:fullerene blends exploiting our well-defined understanding of the microstructures obtained in pBTTT:PCBM systems via processing with fatty acid methyl ester additives. Based on ultrafast transient absorption, electro-absorption, and fluorescence up-conversion spectroscopy, we find that exciton diffusion through relatively phase-pure polymer or fullerene domains limits the rate of electron and hole transfer, while prompt charge separation occurs in regions where the polymer and fullerene are molecularly intermixed (such as the co-crystal phase where fullerenes intercalate between polymer chains in pBTTT:PCBM). We moreover confirm the importance of neat domains, which are essential to prevent geminate recombination of bound electron-hole pairs. Most interestingly, using an electro-absorption (Stark effect) signature, we directly visualize the migration of holes from intermixed to neat regions, which occurs on the subpicosecond time scale. This ultrafast transport is likely sustained by high local mobility (possibly along chains extending from the co-crystal phase to neat regions) and by an energy cascade driving the holes toward the neat domains.
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- 2015
57. Organic photovoltaics: Pushing the knowledge of interfaces
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Natalie, Banerji
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Electric Power Supplies ,Semiconductors - Published
- 2017
58. Charge separation and carrier dynamics in donor-acceptor heterojunction photovoltaic systems
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Majed Chergui, Ariadni Boziki, Ursula Rothlisberger, Jacques-E. Moser, Joël Teuscher, Jean-Pierre Wolf, Natalie Banerji, Andrey L. Stepanov, Jan C. Brauer, and Alicia Solano
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Materials science ,Organic solar cell ,Charge carrier dynamics ,Reviews ,Context (language use) ,02 engineering and technology ,ddc:500.2 ,Dye-sensitized solar cells ,010402 general chemistry ,01 natural sciences ,7. Clean energy ,Photoinduced electron transfer ,Swiss National Center of Competence in Research: Molecular Ultrafast Science and Technology ,Photovoltaics ,lcsh:QD901-999 ,Instrumentation ,Spectroscopy ,Radiation ,Perovskite solar cells ,business.industry ,Photovoltaic system ,Heterojunction ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Solar energy ,Engineering physics ,0104 chemical sciences ,3rd generation photovoltaics ,Photoinduced charge separation ,Organic photovoltaics ,lcsh:Crystallography ,0210 nano-technology ,business ,Ultrafast spectroscopy - Abstract
Electron transfer and subsequent charge separation across donor-acceptor heterojunctions remain the most important areas of study in the field of third- generation photovoltaics. In this context, it is particularly important to unravel the dynamics of individual ultrafast processes (such as photoinduced electron transfer, carrier trapping and association, and energy transfer and relaxation), which prevail in materials and at their interfaces. In the frame of the National Center of Competence in Research “Molecular Ultrafast Science and Technology,” a research instrument of the Swiss National Science Foundation, several groups active in the field of ultrafast science in Switzerland have applied a number of complementary experimental techniques and computational simulation tools to scrutinize these critical photophysical phenomena. Structural, electronic, and transport properties of the materials and the detailed mechanisms of photoinduced charge separation in dye- sensitized solar cells, conjugated polymer- and small molecule-based organic photovoltaics, and high-efficiency lead halide perovskite solar energy converters have been scrutinized. Results yielded more than thirty research articles, an overview of which is provided here.
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- 2017
59. Charge separation in an acceptor–donor–acceptor triad material with a lamellar structure
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Damien Rolland, Lucia Hartmann, Martin Brinkmann, Laure Biniek, Natalie Banerji, Holger Frauenrath, Jan C. Brauer, Ecole Polytechnique Fédérale de Lausanne (EPFL), Institut Charles Sadron (ICS), Université de Strasbourg (UNISTRA)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Réseau nanophotonique et optique, Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Matériaux et nanosciences d'Alsace (FMNGE), Institut de Chimie du CNRS (INC)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS), and University of Fribourg
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Materials science ,Organic solar cell ,Electron donor ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Acceptor ,0104 chemical sciences ,chemistry.chemical_compound ,Crystallography ,[CHIM.POLY]Chemical Sciences/Polymers ,chemistry ,Electron diffraction ,Lamellar phase ,Materials Chemistry ,Side chain ,Lamellar structure ,0210 nano-technology ,Perylene - Abstract
Linking covalently both electron donor and acceptor components is an efficient way to gain thermodynamic control over the formation of well-ordered heterojunction materials suitable for organic photovoltaics. In this context, we attached flexible polymer segments to the termini of a (perylene bisimide)–quaterthiophene–(perylene bisimide) triad. The microphase segregation of the resulting coil-rod-coil architecture served to reliably promote the formation of lamellar phases. The lamellae were oriented vertically relative to the substrate, and they could be laterally aligned by mechanical rubbing, as determined by small and wide angle X-ray scattering, transmission electron microscopy, electron diffraction and AFM. Transient absorption spectroscopy revealed that light absorption was followed by charge separation and that charge recombination was slower in thin films than for solution-phase samples, especially when longer side chains were used. Thus, this study is a first step towards reliable lamellar phase segregation in donor–acceptor materials on the route towards improved materials for organic photovoltaics.
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- 2017
60. Importance of unpaired electrons in organic electronics
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Natalie Banerji, Jian Fan, Rajeev Kumar, Mingfeng Wang, Moureen C. Kemei, Fred Wudl, Michael Bendikov, Toan Pho, Dennis Sheberla, Eneida C. Chesnut, Mariateresa Scarongella, Sebastian Valouch, and Jonathan D. Yuen
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Organic electronics ,Polymers and Plastics ,Ambipolar diffusion ,Band gap ,Chemistry ,Organic Chemistry ,Organic semiconductor ,Unpaired electron ,Chemical physics ,Polymer chemistry ,conjugated polymers ,Materials Chemistry ,Moiety ,EPR ,simulations ,Triplet state ,Open shell ,ESR ,photophysics - Abstract
The first observation that PBBTPD, a low bandgap, ambipolar conjugated donor-acceptor (DA) polymer based on benzobisthiadiazole (BBT), possesses an open-shell singlet ground state as well as a thermally accessible triplet state is described. Similarly, interesting electronic behavior in semiconducting organic DA oligomers based on BBT is also observed. Theoretical predictions have suggested that such behavior is due to the biradicaloid character of BBT and we provide experimental evidence indicating that these predictions are correct. Furthermore, the open shell character strengthens as the conjugation length increases, as observed in the BBT-based polymer, PBBTPD. We show that this biradicaloid structure is observed in each BBT moiety along the chain and that therefore PBBTPD is in fact a polyradicaloid. This observation will most likely aid in the development of better n-type polymeric acceptors for organic semiconductor applications. (c) 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 287-293
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- 2014
61. Charge Separation Pathways in a Highly Efficient Polymer: Fullerene Solar Cell Material
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Natalie Banerji and Arun Aby Paraecattil
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Fullerene ,Exciton ,02 engineering and technology ,Electron ,010402 general chemistry ,01 natural sciences ,7. Clean energy ,Biochemistry ,Catalysis ,Polymer solar cell ,law.invention ,Electron transfer ,Colloid and Surface Chemistry ,law ,Solar cell ,chemistry.chemical_classification ,Chemistry ,business.industry ,General Chemistry ,Polymer ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Chemical physics ,Optoelectronics ,0210 nano-technology ,business ,Excitation - Abstract
PBDTTPD is one of the best conjugated polymers for solar cell applications (up to 8.5% efficiency). We have investigated the dynamics of charge generation in the blend with fullerene (PCBM) and addressed highly relevant topics such as the role of bulk heterojunction structure, fullerene excitation, and excess energy. We show that there are multiple charge separation pathways. These include electron transfer from photoexcited polymer, hole transfer from photoexcited PCBM, prompt (100 fs) charge generation in intimately mixed polymer:fullerene regions (which can occur from hot states), as well as slower electron and hole transfer from excitons formed in pure PBDTTPD or PCBM domains (diffusion to an interface is necessary). Very interestingly, all the charge separation pathways are highly efficient. For example, the yield of long-lived carriers is not significantly affected by the excitation wavelength, although this changes the fraction of photons absorbed by PCBM and the amount of excess energy brought to the system. Overall, the favorable properties of the PBDTTPD:PCBM blend in terms of morphology and exciton delocalization allow excellent charge generation in all circumstances and strongly contribute to the high photovoltaic performance of the blend.
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- 2014
62. The influence of microstructure on charge separation dynamics in organic bulk heterojunction materials for solar cell applications
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Arun Aby Paraecattil, Ester Buchaca-Domingo, Jean M. J. Fréchet, Natalie Stingelin, Mariateresa Scarongella, Jessica D. Douglas, Mario Leclerc, Martin Heeney, Jacques Edouard Moser, Thomas McCarthy-Ward, Serge Beaupré, and Natalie Banerji
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Photocurrent ,chemistry.chemical_classification ,Materials science ,Fullerene ,Organic solar cell ,Renewable Energy, Sustainability and the Environment ,Exciton ,General Chemistry ,Polymer ,7. Clean energy ,Polymer solar cell ,law.invention ,Condensed Matter::Materials Science ,chemistry ,Chemical physics ,law ,Phase (matter) ,Solar cell ,Organic chemistry ,General Materials Science - Abstract
Light-induced charge formation is essential for the generation of photocurrent in organic solar cells. In order to gain a better understanding of this complex process, we have investigated the femtosecond dynamics of charge separation upon selective excitation of either the fullerene or the polymer in different bulk heterojunction blends with well-characterized microstructure. Blends of the pBTTT and PBDTTPD polymers with PCBM gave us access to three different scenarios: either a single intermixed phase, an intermixed phase with additional pure PCBM clusters, or a three-phase microstructure of pure polymer aggregates, pure fullerene clusters and intermixed regions. We found that ultrafast charge separation (by electron or hole transfer) occurs predominantly in intermixed regions, while charges are generated more slowly from excitons in pure domains that require diffusion to a charge generation site. The pure domains are helpful to prevent geminate charge recombination, but they must be sufficiently small not to become exciton traps. By varying the polymer packing, backbone planarity and chain length, we have shown that exciton diffusion out of small polymer aggregates in the highly efficient PBDTTPD:PCBM blend occurs within the same chain and is helped by delocalization.
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- 2014
63. Front Matter: Volume 9923
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Artem A. Bakulin, Robert Lovrincic, and Natalie Banerji
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Materials science ,Nanotechnology ,Nanomaterials - Published
- 2016
64. Carrier dynamics and transport properties in few-layer MoS2 nanoflakes (Conference Presentation)
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Natalie Banerji, Xiaoyun Yu, Demetra Tsokkou, and Kevin Sivula
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Materials science ,business.industry ,Photoconductivity ,Exciton ,Condensed Matter::Materials Science ,chemistry.chemical_compound ,Semiconductor ,chemistry ,Monolayer ,Ultrafast laser spectroscopy ,Optoelectronics ,Direct and indirect band gaps ,business ,Spectroscopy ,Molybdenum disulfide - Abstract
In the last few years, tremendous research interest has been focused on two-dimensional transition metal dichalcogenides, following progress in processing of layers with atomic-size thickness. Among them, molybdenum disulfide (MoS 2 ) nanoflakes have shown unique optical and electrical properties. They are excellent absorbers, despite being ultrathin, with high exciton-binding energies that make excitonic transitions evident even at room temperature. Bulk and few-layer MoS 2 are indirect band gap semiconductors, while its monolayer is a direct band gap semiconductor. Also, bound trions have been reported in monolayer MoS 2 , due to strong interactions between excitons and charges and spatial confinement of the photoexcited species. Ultrafast spectroscopy has brought important clarification to the aforementioned properties in MoS 2 nanoflakes and has unraveled their carrier dynamics and transport properties. However, the strong dependence of the fundamental properties on the nanoflake size and preparation process clearly shows that additional research is needed to understand the rich and unusual photophysics in this system. Therefore, we have used time-resolved absorption and THz transmission spectroscopy to shed light on the photophysical properties of solution-processed, few-layer MoS 2 nanoflakes with subpicosecond temporal resolution. Using different excitation photon energies and fluences, we have resolved the carrier and exciton relaxation, the recombination processes and the corresponding time scales. Also, we have used the spectrum of the complex photoconductivity in the THz region to study the carrier transport properties in the nanoflakes as a function of number of layers.
- Published
- 2016
65. Sub-Picosecond Delocalization in the Excited State of Conjugated Homopolymers and Donor-Acceptor Copolymers
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Natalie Banerji
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Materials science ,Relaxation (NMR) ,02 engineering and technology ,General Chemistry ,Conjugated system ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Photochemistry ,7. Clean energy ,01 natural sciences ,Polymer solar cell ,0104 chemical sciences ,Organic semiconductor ,Partial charge ,Delocalized electron ,Chemical physics ,Excited state ,Materials Chemistry ,Charge carrier ,0210 nano-technology - Abstract
In this feature article, we review and examine evidence that the primary photoexcited species in conjugated polymers is considerably delocalized. Localization occurs via a series of complex relaxation mechanisms on the
- Published
- 2013
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66. Charge Transfer Relaxation in Donor-Acceptor Type Conjugated Materials
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Mariateresa Scarongella, Natalie Banerji, Ursula Rothlisberger, and Andrey Laktionov
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Materials science ,Charge (physics) ,02 engineering and technology ,General Chemistry ,Conjugated system ,010402 general chemistry ,021001 nanoscience & nanotechnology ,7. Clean energy ,01 natural sciences ,Polymer solar cell ,0104 chemical sciences ,Dipole ,Chemical physics ,Computational chemistry ,Excited state ,Intramolecular force ,Ultrafast laser spectroscopy ,Materials Chemistry ,Relaxation (physics) ,0210 nano-technology - Abstract
The development of conjugated materials bearing electron-rich and electron-poor units along their backbone introduces new possibilities to control functionality for organic electronic applications through charge transfer character in ground and excited states. A thorough understanding of intramolecular dipoles and their evolution during excited state relaxation is necessary in order to fully exploit this opportunity. PCDTBT is an alternating donor–acceptor copolymer with high photovoltaic efficiency in bulk heterojunction solar cells. We use time-resolved femtosecond transient absorption spectroscopy in solution and in the solid state to study PCDTBT and the dTBT and CDTBT model compounds, fragments of the polymer chain. Higher solubility and slower relaxation make CDTBT particularly suitable to understand the mechanism of charge transfer relaxation in this class of materials. A progressive increase of charge transfer character from the initially moderately polar excited state is mainly driven by solvent reorganization and some torsional rearrangements. Similar relaxation in solid state CDTBT might ultimately lead to the formation of separate charges.
- Published
- 2013
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67. Dynamics and mechanisms of interfacial photoinduced electron transfer processes of third generation photovoltaics and photocatalysis
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Natalie Banerji, Christophe Bauer, Jacques-E. Moser, Angela Punzi, Jelissa de Jonghe, Elham Ghadiri, Joël Teuscher, Arianna Marchioro, Jan C. Brauer, and Mateusz Wielopolski
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business.industry ,Chemistry ,Molecular electronics ,Nanotechnology ,General Medicine ,General Chemistry ,Photoinduced electron transfer ,Femtochemistry ,Third-generation solar cells ,Photoinduced charge separation ,Chemical physics ,Photovoltaics ,Quantum dot ,Excited state ,Vibrational energy relaxation ,Molecular/bulk heterojunction ,Photocatalysis ,business ,QD1-999 - Abstract
Photoinduced electron transfer (PET) across molecular/bulk interfaces has gained attention only recently and is still poorly understood. These interfaces offer an excellent case study, pertinent to a variety of photovoltaic systems, photo- and electrochemistry, molecular electronics, analytical detection, photography, and quantum confinement devices. They play in particular a key role in the emerging fields of third-generation photovoltaic energy converters and artificial photosynthetic systems aimed at the production of solar fuels, creating a need for a better understanding and theoretical treatment of the dynamics and mechanisms of interfacial PET processes. We aim to achieve a fundamental understanding of these phenomena by designing experiments that can be used to test and alter modern theory and computational modeling. One example illustrating recent investigations into the details of the ultrafast processes that form the basis for photoinduced charge separation at a molecular/bulk interface relevant to dye-sensitized solar cells is briefly presented here: Kinetics of interfacial PET and charge recombination processes were measured by fs and ns transient spectroscopy in a heterogeneous donor-bridge-acceptor (D-B-A) system, where D is a RuII(terpyridyl-PO3)(NCS)3 complex, B an oligo-p-phenylene bridge, and A nanocrystalline TiO2. The forward ET reaction was found to be faster than vibrational relaxation of the vibronic excited state of the donor. Instead, the back ET occurred on the ?s time scale and involved fully thermalized species. The D-A distance dependence of the electron transfer rate was studied by varying the number of p-phenylene units contained in the bridge moiety. The remarkably low damping factor ? = 0.16 Å?1 observed for the ultrafast charge injection from the dye excited state into the conduction band of TiO2 is attributed to the coupling of electron tunneling with nonequilibrium vibrations redistributed on the bridge, giving rise to polaronic transport of charges from the donor ligand to the acceptor solid oxide surface.
- Published
- 2016
68. The fate of electron–hole pairs in polymer:fullerene blends for organic photovoltaics
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Natalie Stingelin, Jelissa De Jonghe-Risse, Jan C. Brauer, Martina Causa, Natalie Banerji, Jacques-Edouard Moser, Mariateresa Scarongella, and Ester Buchaca-Domingo
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Fullerene ,Materials science ,Organic solar cell ,Carrier generation and recombination ,Science ,General Physics and Astronomy ,Nanotechnology ,02 engineering and technology ,010402 general chemistry ,7. Clean energy ,01 natural sciences ,General Biochemistry, Genetics and Molecular Biology ,Article ,symbols.namesake ,Electric field ,MD Multidisciplinary ,Physics::Atomic and Molecular Clusters ,Spectroscopy ,chemistry.chemical_classification ,Multidisciplinary ,General Chemistry ,Polymer ,021001 nanoscience & nanotechnology ,Acceptor ,0104 chemical sciences ,chemistry ,Stark effect ,Chemical physics ,symbols ,0210 nano-technology - Abstract
There has been long-standing debate on how free charges are generated in donor:acceptor blends that are used in organic solar cells, and which are generally comprised of a complex phase morphology, where intermixed and neat phases of the donor and acceptor material co-exist. Here we resolve this question, basing our conclusions on Stark effect spectroscopy data obtained in the absence and presence of externally applied electric fields. Reconciling opposing views found in literature, we unambiguously demonstrate that the fate of photogenerated electron–hole pairs—whether they will dissociate to free charges or geminately recombine—is determined at ultrafast times, despite the fact that their actual spatial separation can be much slower. Our insights are important to further develop rational approaches towards material design and processing of organic solar cells, assisting to realize their purported promise as lead-free, third-generation energy technology that can reach efficiencies over 10%., Charge generation and transport are crucial to the performance of organic solar cells, but the mechanism remains controversial. Causa' et al. show that the phase morphology of polymer:fullerene blends determines the exciton dissociation at femtoseconds, although the spatial separation can occur at picoseconds.
- Published
- 2016
69. Intensity Dependent Femtosecond Dynamics in a PBDTTPD-Based Solar Cell Material
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Natalie Banerji, Mario Leclerc, Serge Beaupré, Arun Aby Paraecattil, and Jacques-E. Moser
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Materials science ,Organic solar cell ,business.industry ,Energy conversion efficiency ,Polymer solar cell ,law.invention ,law ,Solar cell ,Femtosecond ,Ultrafast laser spectroscopy ,Optoelectronics ,General Materials Science ,Charge carrier ,Physical and Theoretical Chemistry ,Thin film ,business - Abstract
PBDTTPD is a conjugated polymer with high power conversion efficiency if used in organic solar cells together with fullerene derivatives. We have investigated forthe first time the excited state dynamics of pristine PBDTTPD thin film as well as the ultrafast evolution of charge carriers in PBDTTPD:PCBM bulk heterojunction blend using femtosecond transient absorption spectroscopy. In the latter, charges appear within the time resolution of the experiment (80% of charges survive after 1 ns; the rest recombines (most probably geminately) on the 200 ps time scale.
- Published
- 2012
70. Breaking Down the Problem: Optical Transitions, Electronic Structure, and Photoconductivity in Conjugated Polymer PCDTBT and in Its Separate Building Blocks
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Eric Gagnon, Sebastian Valouch, Mario Leclerc, Jung Hwa Seo, Alan J. Heeger, Natalie Banerji, Pierre-Yves Morgantini, and Ali Mohebbi
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Materials science ,Absorption spectroscopy ,Band gap ,Electronic structure ,Photochemistry ,Acceptor ,Polymer solar cell ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Delocalized electron ,Partial charge ,General Energy ,Chemical physics ,Absorption band ,Physical and Theoretical Chemistry - Abstract
Conjugated polymers with alternating electron- withdrawing and electron-donating groups along their back- bone (donor−acceptor copolymers) have recently attracted attention due to high power conversion efficiency in bulk heterojunction solar cells. In an effort to understand how the bandgap in a typical donor−acceptor copolymer is reduced by internal charge transfer character and what the implications of this charge transfer are, we have synthesized the isolated repeat unit (CDTBT) of the photovoltaically highly successful PCDTBT polymer. We compare here the spectroscopic and electrochemical properties of the polymer, the repeat unit, and the separate carbazole donor and dithienylbenzothiadiazole acceptor moieties (CB and dTBT, respectively) in the solid state and in solutions of various polarity. The results are interpreted with the help of time-dependent density functional theory (TD-DFT) calculations. We identify the dominant electronic transitions responsible for the first two absorption bands in the "camel back" spectrum of PCDTBT as partial charge transfer transitions with significant delocalization in the directly excited states. The low bandgap, overall shape, and partial charge transfer character of the PCDTBT absorption spectrum originate from transitions in the dTBT unit. The attached CB moiety extends the conjugation length in CDTBT, rather than acting as a localized donor. Further electronic delocalization, leading to a relatively small reduction in bandgap, occurs upon polymerization. We use our finding of higher delocalization following excitation in the second absorption band to explain the increased yield of photogenerated charges from this band in PCDTBT solid thin films. Moreover, we point out the importance of initial delocalization in the functioning of bulk heterojunction solar cells. The results presented here are therefore not only highly important for a better understanding of donor−acceptor copolymers in general but can also potentially guide the strategic development of future photovoltaic materials.
- Published
- 2012
71. Charge Formation, Recombination, and Sweep-Out Dynamics in Organic Solar Cells
- Author
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Natalie Banerji, Wei Lin Leong, Sarah R. Cowan, and Alan J. Heeger
- Subjects
Materials science ,Organic solar cell ,business.industry ,Photovoltaic system ,Hybrid solar cell ,Condensed Matter Physics ,Solar energy ,Polymer solar cell ,Electronic, Optical and Magnetic Materials ,law.invention ,Biomaterials ,Photoexcitation ,law ,Solar cell ,Electrochemistry ,Optoelectronics ,Charge carrier ,business - Abstract
This article presents a critical discussion of the various physical processes occurring in organic bulk heterojunction (BHJ) solar cells based on recent experimental results. The investigations span from photoexcitation to charge separation, recombination, and sweep-out to the electrodes. Exciton formation and relaxation in poly[N-9?-hepta-decanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole) (PCDTBT) and poly-3(hexylthiophene) (P3HT) are discussed based on a fluorescence up-conversion study. The commonly accepted paradigm describing the conversion of incident photons into charge carriers in the BHJ material is re-examined in light of these femtosecond time-resolved measurements. Transient photoconductivity, time-delayed collection field, and time-delayed dual pulse experiments carried out on BHJ solar cells demonstrate the competition between carrier sweep-out by the internal field and the loss of photogenerated carriers by recombination. Finally, an emerging hypothesis is discussed: that bimolecular recombination accounts for the majority of recombination from short circuit to open circuit in optimized solar cells, and that bimolecular recombination is bias- and charge-density-dependent. The study of recombination loss processes in organic solar cells leads to insights into what must be accomplished to achieve the ideal solar cell.
- Published
- 2012
72. Exciton Formation, Relaxation, and Decay in PCDTBT
- Author
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Alan J. Heeger, Mario Leclerc, Natalie Banerji, Sarah R. Cowan, and Eric Vauthey
- Subjects
Chemistry ,Exciton ,Relaxation (NMR) ,Time evolution ,General Chemistry ,Electron ,Biochemistry ,Fluorescence ,Catalysis ,Colloid and Surface Chemistry ,Chemical physics ,ddc:540 ,Atomic physics ,Thin film ,Spectroscopy ,Excitation - Abstract
The nature and time evolution of the primary excitations in the pristine conjugated polymer, PCDTBT, are investigated by femtosecond-resolved fluorescence up-conversion spectroscopy. The extensive study includes data from PCDTBT thin film and from PCDTBT in chlorobenzene solution, compares the fluorescence dynamics for several excitation and emission wavelengths, and is complemented by polarization-sensitive measurements. The results are consistent with the photogeneration of mobile electrons and holes by interband π−π* transitions, which then self-localize within about 100 fs and evolve to a bound singlet exciton state in less than 1 ps. The excitons subsequently undergo successive migrations to lower energy localized states, which exist as a result of disorder. In parallel, there is also slow conformational relaxation of the polymer backbone. While the initial self-localization occurs faster than the time resolution of our experiment, the exciton formation, exciton migration, and conformational changes lead to a progressive relaxation of the inhomogeneously broadened emission spectrum with time constants ranging from about 500 fs to tens of picoseconds. The time scales found here for the relaxation processes in pristine PCDTBT are compared to the time scale (
- Published
- 2010
73. Tuning the Excited-State Dynamics of GFP-Inspired Imidazolone Derivatives
- Author
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Vladimir Dimitrov, Irina Petkova, Peter Nikolov, Natalie Banerji, Guillaume Duvanel, Robert Perez, Eric Vauthey, and Georgi M. Dobrikov
- Subjects
Physics::Biological Physics ,Quantitative Biology::Biomolecules ,Molecular Structure ,Absorption spectroscopy ,Chemistry ,Green Fluorescent Proteins ,Imidazoles ,Substituent ,Stereoisomerism ,Chromophore ,Photochemistry ,chemistry.chemical_compound ,Models, Chemical ,Excited state ,Intramolecular force ,ddc:540 ,Ultrafast laser spectroscopy ,Computer Simulation ,Physics::Chemical Physics ,Physical and Theoretical Chemistry ,Spectroscopy ,Conformational isomerism - Abstract
The excited-state dynamics of five derivatives of the GFP-chromophore, which differ by the position and nature of their substituents, has been investigated in solvents of various viscosity and polarity and in rigid media using femtosecond-resolved spectroscopy. In polar solvents of low viscosity, like acetonitrile or methanol, the fluorescence decays of all compounds are multiexponential, with average lifetimes of the order of a few picoseconds, whereas in rigid matrices (polymer films and low temperature glasses), they are single exponential with lifetimes of the order of a few nanoseconds and fluorescence quantum yields close to unity. Global analysis of the fluorescence decays recorded at several wavelengths and of the transient absorption spectra reveals the presence of several excited-state populations with slightly different fluorescence and absorption spectra and with distinct lifetimes. These populations are attributed to the existence of multiple ground-state conformers. From the analysis of the dependence of the excited-state dynamics on the solvent and on the nature of the substituents, it follows that the nonradiative deactivation of all these excited chromophores involves an intramolecular coordinate with large amplitude motion. However, depending on the solvent and substituent, additional channels, namely, inter- and intramolecular hydrogen bond assisted nonradiative deactivation, are operative. This allows tuning of the excited-state lifetime of the chromophore. Finally, an ultrafast photoinduced intramolecular charge transfer is observed in polar solvents with one derivative bearing a dimethylaminophenyl substituent.
- Published
- 2009
74. Ordered and oriented supramolecular n/p-heterojunction surface architectures: completion of the primary color collection
- Author
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Guillaume Bollot, Stefan Matile, Michal Borkovec, Natalie Banerji, Alberto Gomez-Casado, Oksana Kel, Daniel Emery, Jurriaan Huskens, Ravuri S. K. Kishore, Naomi Sakai, Eric Vauthey, Plinio Maroni, Jiri Mareda, Pascal Jonkheijm, Molecular Nanofabrication, and Faculty of Science and Technology
- Subjects
Photocurrent ,METIS-259879 ,Zipper ,Chemistry ,Supramolecular chemistry ,Color ,Nanotechnology ,Heterojunction ,General Chemistry ,Quartz crystal microbalance ,Electrochemical Techniques ,Naphthalenes ,Imides ,Biochemistry ,Catalysis ,Colloid and Surface Chemistry ,Primary color ,Photoinduced charge separation ,IR-76906 ,Electrode ,ddc:540 - Abstract
In this study, we describe synthesis, characterization, and zipper assembly of yellow p-oligophenyl naphthalenediimide (POP-NDI) donor-acceptor hybrids. Moreover, we disclose, for the first time, results from the functional comparison of zipper and layer-by-layer (LBL) assembly as well as quartz crystal microbalance (QCM), atomic force microscopy (AFM), and molecular modeling data on zipper assembly. Compared to the previously reported blue and red NDIs, yellow NDIs are more pi-acidic, easier to reduce, and harder to oxidize. The optoelectronic matching achieved in yellow POP-NDIs is reflected in quantitative and long-lived photoinduced charge separation, comparable to their red and much better than their blue counterparts. The direct comparison of zipper and LBL assemblies reveals that yellow zippers generate more photocurrent than blue zippers as well as LBL photosystems. Continuing linear growth found in QCM measurements demonstrates that photocurrent saturation at the critical assembly thickness occurs because more charges start to recombine before reaching the electrodes and not because of discontinued assembly. The found characteristics, such as significant critical thickness, strong photocurrents, large fill factors, and, according to AFM images, smooth surfaces, are important for optoelectronic performance and support the existence of highly ordered architectures.
- Published
- 2009
75. Excited-State Dynamics of Donor−Acceptor Bridged Systems Containing a Boron−Dipyrromethene Chromophore: Interplay between Charge Separation and Reorientational Motion
- Author
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Guillaume Duvanel, Natalie Banerji, and Eric Vauthey
- Subjects
chemistry.chemical_compound ,chemistry ,Covalent bond ,Triptycene ,Excited state ,ddc:540 ,Molecule ,Single bond ,Moiety ,Physical and Theoretical Chemistry ,Chromophore ,Photochemistry ,Acceptor - Abstract
The excited-state dynamics of a series of electron donor-acceptor bridged systems (DABS) consisting of a boron-dipyrromethene chromophore covalently linked to a dinitro-substituted triptycene has been investigated using femtosecond time-resolved spectroscopy. The chromophores differ by the number of bromine atom substituents. The fluorescence lifetime of the DABS without any bromine atom is strongly reduced when going from toluene to polar solvents, this shortening being already present in chloroform. This effect is about 10 times weaker with a single bromine atom and negligible with two bromine atoms on the chromophore. The excited-state lifetime shortening is ascribed to a charge transfer from the excited chromophore to a nitrobenzene moiety, the driving force of this process depending on the number of bromine substituents. The occurrence of this process is further confirmed by the investigation of the excited-state dynamics of the chromophore alone in pure nitrobenzene. Surprisingly, no correlation between the charge separation time constant and the dielectric properties of the solvents could be observed. However, a good correlation between the charge separation time constant and the diffusional reorientation time of the chromophore alone, measured by fluorescence anisotropy, was found. Quantum chemistry calculations suggest that quasi-free rotation about the single bond linking the chromophore to the triptycene moiety permits a sufficient coupling of the donor and the acceptor to ensure efficient charge separation. The charge separation dynamics in these molecules is thus controlled by the reorientational motion of the donor relative to the acceptor.
- Published
- 2007
76. Using the Stark effect to understand charge generation in organic solar cells
- Author
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Natalie Stingelin, Jacques-E. Moser, Martin Heeney, Martina Causa, Jelissa De Jonghe-Risse, Natalie Banerji, and Ester Buchaca-Domingo
- Subjects
Fullerene ,Materials science ,Organic solar cell ,Organic solar cells ,Stark effect ,Electromodulated differential absorption ,02 engineering and technology ,Charge transport ,010402 general chemistry ,01 natural sciences ,7. Clean energy ,law.invention ,Charge generation ,symbols.namesake ,law ,Phase (matter) ,Solar cell ,Absorption (electromagnetic radiation) ,chemistry.chemical_classification ,business.industry ,Charge (physics) ,Polymer ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,chemistry ,Chemical physics ,symbols ,Optoelectronics ,0210 nano-technology ,business ,Ultrafast spectroscopy - Abstract
We have used a femtosecond-resolved spectroscopic technique based on the Stark effect (electromodulated differential absorption) in order to investigate free charge generation and charge drift in solar cell devices of neat conjugated polymer pBTTT and in its 1:1 (by weight) blend with PCBM. In the latter, the fullerene molecules intercalate between the polymer side-chains, yielding a co-crystal phase. Our results show that free charge generation in both materials is ultrafast and strongly dependent on the applied reverse bias. Charge drift to the electrodes (under strong reverse bias) occurs with comparable dynamics on the 1.2 ns time scale for neat pBTTT and the blend, and is probably dominated by hole transport within/between polymer chains.
- Published
- 2015
77. Photoinduced Bimolecular Electron Transfer Investigated by Femtosecond Time-Resolved Infrared Spectroscopy
- Author
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Natalie Banerji, Bernhard Felix Lang, Omar F. Mohammed, Erik T. J. Nibbering, and Eric Vauthey
- Subjects
Exergonic reaction ,Chemistry ,Infrared spectroscopy ,Photochemistry ,Electron transfer ,Two-dimensional infrared spectroscopy ,Excited state ,Molecular vibration ,ddc:540 ,Ultrafast laser spectroscopy ,Physics::Atomic and Molecular Clusters ,Physics::Chemical Physics ,Physical and Theoretical Chemistry ,Spectroscopy - Abstract
Ultrafast infrared transient absorption spectroscopy is used to study the photoinduced bimolecular electron transfer reaction between perylene in the first singlet excited state and 1,4-dicyanobenzene in acetonitrile and dichloromethane. Following vibrational marker modes on both donor and acceptor sides in real time provides direct insight into the structural dynamics during the reaction. A band narrowing on a time scale of a few tens of picoseconds observed on the antisymmetric CN stretching vibration of the dicyanobenzene radical anion indicates that a substantial part of the excess energy is channeled into vibrational modes of the product, despite the fact that the reaction is weakly exergonic. An additional narrowing of the same band on a time scale of several hundreds of picoseconds observed in acetonitrile only is interpreted as a signature of the dissociation of the geminate ion pairs into free ions.
- Published
- 2006
78. Towards the stereoselective synthesis of inherently chiral pseudorotaxanes
- Author
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Jérôme Lacour, Gérald Bernardinelli, Pierre Mobian, and Natalie Banerji
- Subjects
Tris ,19f nmr spectroscopy ,Stereochemistry ,Organic Chemistry ,Biochemistry ,Medicinal chemistry ,Ion ,chemistry.chemical_compound ,Enantiopure drug ,TRISPHAT ,chemistry ,ddc:540 ,Ammonium ,Stereoselectivity ,Physical and Theoretical Chemistry - Abstract
Herein is reported an investigation towards the stereoselective synthesis of inherently chiral pseudorotaxanes. Chiral ammonium threads were readily prepared in five steps from racemic or enantiopure (M or P) salts of di-n-propyl-1,13-dimethoxyquinacridinium cation. Their self-assembly with DB24C8 or disymmetrically oriented DB24C8F6 rings formed pseudorotaxanes as shown by 1H and 19F NMR spectroscopy as well as MS measurements. A determination of the association constants (Ka) was afforded. The crucial role played by the ammonium counter-ion in the threading process was further demonstrated as salts of TRISPHAT (tris(tetrachlorobenzenediolato)phosphate(V)) anion were quite more effective than their PF6- analogues (x 7.3). A general lack of diastereoselectivity (de
- Published
- 2006
79. Effect of the Excitation Wavelength on the Ultrafast Charge Recombination Dynamics of Donor−Acceptor Complexes in Polar Solvents
- Author
-
Natalie Banerji, Olivier Nicolet, Stéphane Pagès, and Eric Vauthey
- Subjects
Pyromellitic dianhydride ,Solvation ,Tetracyanoethylene ,chemistry.chemical_compound ,Wavelength ,chemistry ,Absorption band ,Chemical physics ,ddc:540 ,Polar ,Physics::Chemical Physics ,Physical and Theoretical Chemistry ,Atomic physics ,Spectroscopy ,Excitation - Abstract
The effect of the excitation wavelength on the charge recombination (CR) dynamics of several donor−acceptor complexes (DACs) composed of benzene derivatives as donors and of tetracyanoethylene or pyromellitic dianhydride as acceptors has been investigated in polar solvents using ultrafast time-resolved spectroscopy. Three different wavelength effects have been observed. (1) With complexes exhibiting two well-separated charge-transfer bands, the CR dynamics was found to be slower by a factor of about 1.5 upon excitation in the high-energy band. This effect was measured in both fast and slow relaxing solvents and was discussed in terms of different DAC geometries. (2) When the CR is faster than diffusive solvation, a slowing down of the CR with increasing excitation wavelength accompanied by an increase of the nonexponential character of the dynamics was measured. This effect appears only when exciting on the red edge of the charge-transfer absorption band. (3) When the driving force for CR is small, both nonequilibrium (hot) and thermally activated CR pathways can be operative. The results obtained with such a complex indicate that the relative contribution of these two paths depends on the excitation wavelength.
- Published
- 2005
80. Front Matter: Volume 9165
- Author
-
Sophia C. Hayes, Natalie Banerji, and Carlos Silva
- Subjects
Materials science ,Volume (thermodynamics) ,Mechanics ,Front (military) - Published
- 2014
81. Charge separation in an n-p-n triad forming Lamellar structure (presentation video)
- Author
-
Damien Rolland, Holger Frauenrath, Natalie Banerji, Martin Brinkmann, and Lucia Hartmann
- Subjects
Photoluminescence ,Materials science ,Absorption spectroscopy ,Organic solar cell ,business.industry ,Charge (physics) ,chemistry.chemical_compound ,Semiconductor ,chemistry ,Chemical physics ,Ultrafast laser spectroscopy ,Optoelectronics ,Lamellar structure ,business ,Perylene - Abstract
Since charge separation in organic photovoltaics takes place between n- and p-type semiconductors, their interface should be maximized within the active layer, while charge percolation pathways to the electrodes should be ensured. One way to obtain an ideal and thermodynamically stable morphology is to covalently link n- and p-type semiconductors, provided a sufficiently high internal order is achieved. To this end, we have synthesized a perylene-quaterthiophene-perylene triad substituted with poly(isobutene) segments that induce order at the nanoscale via microphase segregation. Charge separation under selective illumination on the quaterthiophene or perylene moiety was investigated by steady state and transient absorption spectroscopy, and related to the molecular packing and phase morphology deduced from electron and grazing incidence X-ray diffractions. Photoluminescence was quenched due to charge separation within the triad. In solution, these charges quickly recombined, but were shown to have a longer lifetime in films, which is beneficial for charge collection in photovoltaic devices. We have also investigated whether alignment of the supramolecular aggregates affects the photophysics.
- Published
- 2014
82. Photoproduction of Proton Gradients with π-Stacked Fluorophore Scaffolds in Lipid Bilayers
- Author
-
Natalie Banerji, Eric Vauthey, Guillaume Bollot, Naomi Sakai, Stefan Matile, Frank Würthner, Pinaki Talukdar, Sheshanath V. Bhosale, Adam L. Sisson, Cornelia Röger, Jiri Mareda, and Alexandre Fürstenberg
- Subjects
Fluorophore ,Light ,Photochemistry ,Lipid Bilayers ,Analytical chemistry ,Electrons ,Naphthalenes ,Imides ,Ligands ,chemistry.chemical_compound ,Diimide ,Synthetic ion channels ,Benzene Derivatives ,Benzoquinones ,Lipid bilayer ,Edetic Acid ,Multidisciplinary ,Molecular Structure ,Chemistry ,Bilayer ,Temperature ,Chromophore ,Quinone ,Thermodynamics ,Protons ,Oxidation-Reduction ,Perylene ,Phenanthrolines - Abstract
Rigid p -octiphenyl rods were used to create helical tetrameric π-stacks of blue, red-fluorescent naphthalene diimides that can span lipid bilayer membranes. In lipid vesicles containing quinone as electron acceptors and surrounded by ethylenediaminetetraacetic acid as hole acceptors, transmembrane proton gradients arose through quinone reduction upon excitation with visible light. Quantitative ultrafast and relatively long-lived charge separation was confirmed as the origin of photosynthetic activity by femtosecond fluorescence and transient absorption spectroscopy. Supramolecular self-organization was essential in that photoactivity was lost upon rod shortening (from p -octiphenyl to biphenyl) and chromophore expansion (from naphthalene diimide to perylene diimide). Ligand intercalation transformed the photoactive scaffolds into ion channels.
- Published
- 2006
83. Front Matter: Volume 8811
- Author
-
Carlos Silva and Natalie Banerji
- Subjects
Volume (thermodynamics) ,Mechanics ,Geology ,Front (military) - Published
- 2013
84. Ultrafast spectroscopic investigation of a fullerene poly(3-hexylthiophene) dyad
- Author
-
Jason Seifter, Fred Wudl, Natalie Banerji, Mingfeng Wang, Alan J. Heeger, and Eric Vauthey
- Subjects
Materials science ,Organic solar cell ,Photoinduced Charge Separation ,Solar-Cells ,Electron-Transfer ,02 engineering and technology ,010402 general chemistry ,Photochemistry ,7. Clean energy ,01 natural sciences ,Micelle ,Photocurrent Generation ,Polymer solar cell ,Ultrafast laser spectroscopy ,Double-Cable Polymers ,Polymer Photovoltaic Cells ,Quenching (fluorescence) ,Excited-State Dynamics ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Acceptor ,0104 chemical sciences ,Electronic, Optical and Magnetic Materials ,Photoinduced charge separation ,ddc:540 ,Charge carrier ,Organic Photovoltaics ,0210 nano-technology ,Conjugated Polymer ,Photophysical Properties - Abstract
We present the femtosecond spectroscopic investigation of a covalently linked dyad, PCB-P3HT, formed by a segment of the conjugated polymer P3HT (regioregular poly(3-hexylthiophene)) that is end capped with the fullerene derivative PCB ([6,6]-phenyl-C-61-butyric acid ester), adapted from PCBM. The fluorescence of the P3HT segment in tetrahydrofuran (THF) solution is reduced by 64% in the dyad compared to a control compound without attached fullerene (P3HT-OH). Fluorescence upconversion measurements reveal that the partial fluorescence quenching of PCB-P3HT in THF is multiphasic and occurs on an average time scale of 100 ps, in parallel to excited-state relaxation processes. Judging from ultrafast transient absorption experiments, the origin of the quenching is excitation energy transfer from the P3HT donor to the PCB acceptor. Due to the much higher solubility of P3HT compared to PCB in THF, the PCB-P3HT dyad molecules self-assemble into micelles. When pure C-60 is added to the solution, it is incorporated into the fullerene-rich center of the micelles. This dramatically increases the solubility of C-60 but does not lead to significant additional quenching of the P3HT fluorescence by the C-60 contained in the micelles. In PCB-P3HT thin films drop-cast from THF, the micelle structure is conserved. In contrast to solution, quantitative and ultrafast (
- Published
- 2011
85. Ultrafast Relaxation of the Poly(3-hexylthiophene) Emission Spectrum
- Author
-
Natalie Banerji, Sarah R. Cowan, Eric Vauthey, and Alan J. Heeger
- Subjects
Materials science ,Conjugated Polymers ,Analytical chemistry ,02 engineering and technology ,Plastic Solar-Cells ,010402 general chemistry ,01 natural sciences ,Molecular physics ,Delocalized electron ,Emission spectrum ,Physical and Theoretical Chemistry ,Spectroscopy ,Absorption (electromagnetic radiation) ,Polymer Photovoltaic Cells ,Poly(Phenylene Vinylene) ,Charge Photogeneration ,Electroluminescent Polymers ,Relaxation (NMR) ,Excited-State Dynamics ,021001 nanoscience & nanotechnology ,Fluorescence ,3. Good health ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Photoexcitation ,General Energy ,ddc:540 ,Regioregular Poly(3-Hexylthiophene) ,Time-resolved spectroscopy ,Time-Resolved Fluorescence ,0210 nano-technology ,Polarized-Electroabsorption Spectroscopy - Abstract
The femtosecond-resolved evolution of the emission spectrum of the important conjugated polymer poly(3-hexylthiophene) (P3HT) is presented. Detailed fluorescence up-conversion spectroscopy was performed on P3HT solid-state films and on P3HT in chlorobenzene solution. Two excitation wavelengths and several emission wavelengths, covering the entire fluorescence spectrum, were used. The data were complemented by polarization-sensitive measurements. Our global analysis allowed a reconstruction of the time-resolved emission spectra with 200 Is temporal resolution, so that spectral changes due to the early relaxation processes following pi-pi* interband absorption in the pristine polymer could be comprehensively characterized. Absorption occurs in isolated polymer chains in solution and in the solid state (including interchain interactions) for the film. In both cases, we find evidence of delocalization of the electrons and holes formed in the energy bands directly after photoexcitation with excess energy. This is followed by ultrafast (similar to 100 fs) self-localization of the primary photoexcitation and by relatively slow exciton formation (similar to 1 ps). Further relaxation occurs with time constants ranging from hundreds of femtoseconds to tens of picoseconds, due to exciton hopping to sites with lower energy and to a slow conformational planarization of the polymer backbone. Depolarization, a spectral red shift, and important changes in the vibronic structure are observed as a consequence of this relaxation. Finally, relaxed intrachain and interchain singlet excitons are formed in solution and film, respectively, on a 100-200 ps time scale. They decay with a similar to 500 ps time constant, by intersystem crossing in solution and by nonradiative recombination in the film. Our results are consistent with and strongly support the conclusions we obtained from a similar time-resolved fluorescence study of the polymer PCDTBT (J. Am. Chem. Soc. 2010, 132, 17459): ultrafast charge separation in polymer:fullerene blends seems to occur before localization of the primary excitation to form a bound exciton.
- Published
- 2011
86. Ultrafast excited-state dynamics of strongly coupled porphyrin/core-substituted-naphthalenediimide dyads
- Author
-
Eric Vauthey, Steven J. Langford, Sheshanath V. Bhosale, Irina Petkova, and Natalie Banerji
- Subjects
Geminate Ion-Pairs ,Charge-Recombination Dynamics ,Energy-Transfer ,Photoinduced Electron-Transfer ,Optical-Properties ,General Physics and Astronomy ,Quantum yield ,Photochemistry ,Porphyrin ,Acceptor ,Quantum chemistry ,Photoinduced electron transfer ,Separation ,chemistry.chemical_compound ,chemistry ,Building-Blocks ,Excited state ,ddc:540 ,Molecule ,Physical and Theoretical Chemistry ,Triplet state ,Physics::Chemical Physics ,Arrays ,Multichromophoric Systems - Abstract
The photophysics and excited-state dynamics of two dyads consisting of either a free-base or a zinc-tetraphenylporphyrin linked through a rigid bridge to a core-substituted naphthalenediimide (NDI) have been investigated by femtosecond-resolved spectroscopy. The absorption and fluorescence spectra differ substantially from those of the individual units, pointing to a substantial coupling and to a delocalisation of the excitation over the whole molecule, as confirmed by quantum chemistry calculations. A strong dependence of their excited-state dynamics on the solvent polarity has been observed. In toluene, the fluorescence quantum yield of the dyads is of the order of a few percent and the main decay channel of the emitting state is proposed as intersystem-crossing to the triplet state. However, in a medium polarity solvent like dichloromethane, the emitting state undergoes charge separation from the porphyrin to the NDI unit within 1-3 ps, and the ensuing charge-separated state recombines in about 10-20 ps. This solvent dependence can be explained by the weak driving force for charge separation in polar solvents and the large electronic coupling between the porphyrin and NDI moieties, making charge separation a solvent-controlled adiabatic process.
- Published
- 2011
87. Highly Exergonic Bimolecular Electron Transfer Beyond Marcus Theory, the Importance of Molecular Structure and Dynamics
- Author
-
Katrin Adamczyk, Eric Vauthey, Jens Dreyer, Bernhard Felix Lang, Diego Villamaina, Erik T. J. Nibbering, and Natalie Banerji
- Subjects
Exergonic reaction ,Electron transfer ,Computational chemistry ,Chemistry ,Chemical physics ,Ultrafast laser spectroscopy ,Mid infrared ,Molecule ,Marcus theory - Abstract
The combination of visible and mid infrared transient absorption yields a direct insight into structural dynamics and determination of distinct reaction pathways in highly exergonic electron transfer, asking for refinement of existing theories.
- Published
- 2010
88. Kinetic control in the chiral recognition of three-bladed propellers
- Author
-
Clément Bonnot, Enrique Espinosa, Emmanuel Aubert, Jean-Claude Chambron, Jérôme Lacour, and Natalie Banerji
- Subjects
Cryptands ,Ion pairs ,Proton ,Stereochemistry ,Organic Chemistry ,Kinetics ,Diastereomer ,Protonation ,General Chemistry ,Nuclear magnetic resonance spectroscopy ,Toluene ,Catalysis ,chemistry.chemical_compound ,Crystallography ,Deprotonation ,chemistry ,ddc:540 ,Solvent effects ,Helical structures - Abstract
The ion pair of the stereolabile C(3)-symmetric, i(+)o proton complex [1H](+) of diaza-macropentacycle 1 and the configurationally stable Delta-TRISPHAT ([Delta-3](-)) anion exists in the form of two diastereomers, namely, [Delta-(1.H)][Delta-3] and [Lambda-(1.H)][Delta-3], the ratio of which, in terms of diastereomeric excess (de) decreases in the order [D(8)]THF (28%)CD(2)Cl(2) (22%)CDCl(3) (20%)[D(8)]toluene (16%)C(6)D(6) (7%)[D(6)]acetone (0%) at thermodynamic equilibrium. Except in the case of [D(6)]acetone, the latter is reached after a period of time that increases from 1 h ([D(8)]THF) to 24 h (CDCl(3)). Moreover, the initial value of the de of [1.H][Delta-3] in CDCl(3), before the thermodynamic equilibrium is reached, depends on the solvent in which the sample has been previously equilibrated (sample "history"). This property has been used to show that the crystals of [1.H][Delta-3] formed by slow evaporation of CH(2)Cl(2)/CH(3)OH mixtures had 100% de, which indicates that [1.H][Delta-3] has enjoyed a crystallization-induced asymmetric transformation. Structural studies in solution (NMR spectroscopy) and in the gas phase by calculations at the semiempirical PM6 level of theory suggest that the optically active anion is docked on the i(+) (endo) external side of the proton complex such that one of the aromatic rings of [Delta-3](-) is inserted into a groove of [1.H](+), a second aromatic ring being placed astride the outside i(+) pocket. Solvent polarity controls the thermodynamics of inversion of the [1.H](+) propeller. However, both polarity and basicity control its kinetics. Therefore, the rate-limiting steps correspond to the ion-pair separation/recombination and [1.H](+)/1 deprotonation/protonation processes, rather than the inversion of [1H](+), the latter being likely to take place in the deprotonated form (1).
- Published
- 2010
89. Artificial tongues and leaves
- Author
-
Velayutham Ravikumar, Alexandre Fürstenberg, Natalie Banerji, Eric Vauthey, Guillaume Bollot, Rajesh S. Bhosale, Sara Marie Butterfield, Ravuri S. K. Kishore, Santanu Maity, Virginie Gorteau, Duy-Hien Tran, Naomi Sakai, Alejandro Oscar Perez-Velasco, Stefan Matile, Federico Mora, Shinya Hagihara, Andreas Hennig, and Jiri Mareda
- Subjects
Scaffolds ,Complex matrix ,Nanoarchitecture ,Chemistry ,business.industry ,Sensors ,General Chemical Engineering ,Nanotechnology ,General Chemistry ,Artificial photosynthesis ,Lipid bilayer ,Photovoltaics ,Membrane ,ddc:540 ,Photosynthesis ,business - Abstract
The objective with synthetic multifunctional nanoarchitecture is to create large suprastructures with interesting functions. For this purpose, lipid bilayer membranes or conducting surfaces have been used as platforms and rigid-rod molecules as shape-persistent scaffolds. Examples for functions obtained by this approach include pores that can act as multicomponent sensors in complex matrices or rigid-rod π-stack architecture for artificial photosynthesis and photovoltaics.
- Published
- 2008
90. Rigid-rod push-pull naphthalenediimide photosystems
- Author
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Sheshanath V. Bhosale, Alexandre Fürstenberg, Naomi Sakai, Eric Vauthey, Natalie Banerji, Stefan Matile, and Adam L. Sisson
- Subjects
genetic structures ,Chemistry ,Organic Chemistry ,Nanotechnology ,Biochemistry ,Rod ,Photoinduced charge separation ,Chemical physics ,ddc:540 ,Rigid rod ,sense organs ,Physical and Theoretical Chemistry ,Push pull ,Photosystem - Abstract
Design, synthesis and evaluation of advanced rigid-rod pi-stack photosystems with asymmetric scaffolds are reported. The influence of push-pull rods on self-organization, photoinduced charge separation and photosynthetic activity is investigated and turns out to be surprisingly small overall.
- Published
- 2007
91. Charge generation in organic solar cell materials studied by terahertz spectroscopy
- Author
-
Mariateresa Scarongella, Jean M. J. Fréchet, Natalie Banerji, Jessica D. Douglas, Jan C. Brauer, Kafafi, Zh, Lane, Pa, and Samuel, Idw
- Subjects
Materials science ,Organic solar cell ,business.industry ,Terahertz radiation ,Organic solar cells ,Exciton ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,terahertz spectroscopy ,01 natural sciences ,7. Clean energy ,Fluence ,mobility ,0104 chemical sciences ,Terahertz spectroscopy and technology ,Delocalized electron ,Orders of magnitude (time) ,conjugated polymers ,Optoelectronics ,0210 nano-technology ,business ,Spectroscopy ,charge generation - Abstract
We have investigated the photophysics in neat films of conjugated polymer PBDTTPD and its blend with PCBM using terahertz time-domain spectroscopy. This material has very high efficiency when used in organic solar cells. We were able to identify a THz signature for bound excitons in neat PBDTTPD films, pointing to important delocalization in those excitons. Then, we investigated the nature and local mobility (orders of magnitude higher than bulk mobility) of charges in the PBDTTPPD:PCBM blend as a function of excitation wavelength, fluence and pump-probe time delay. At low pump fluence (no bimolecular recombination phenomena), we were able to observe prompt and delayed charge generation components, the latter originating from excitons created in neat polymer domains which, thanks to delocalization, could reach the PCBM interface and dissociate to charges on a time scale of 1 ps. The nature of the photogenerated charges did not change between 0.5 ps and 800 ps after photo-excitation, which indicated that the excitons split directly into relatively free charges on an ultrafast time scale.
- Published
- 2015
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92. Optoelectronically mismatched oligophenylethynyl-naphthalenediimide SHJ architectures
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Rajesh S. Bhosale, Stefan Matile, Santanu Maity, Eric Vauthey, Natalie Banerji, and Naomi Sakai
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Zipper ,Absorption spectroscopy ,Photochemistry ,Molecular Conformation ,Stacking ,Supramolecular chemistry ,Nanotechnology ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Electron Transport ,Electron transfer ,Physical and Theoretical Chemistry ,Absorption (electromagnetic radiation) ,Photocurrent ,Molecular Structure ,010405 organic chemistry ,business.industry ,Chemistry ,Phenyl Ethers ,Organic Chemistry ,Planarity testing ,0104 chemical sciences ,Naphthalimides ,Spectrophotometry ,Alkynes ,ddc:540 ,Optoelectronics ,business - Abstract
The objective of this study was to evaluate the possibility of photoinduced stack/rod electron transfer in surface "zipper" architectures composed of stacks of blue (B) naphthalenediimides (NDIs) along strings of oligophenylethynyl (OPE) rods. The synthesis and characterization of anionic and cationic multichromophoric OPE-B systems are reported. Absorption spectra suggest that in OPE-B systems, planarity and thus absorption and conductivity of the OPE can possibly be modulated by intramolecular stacking of the surrounding NDIs, although interfering contributions from aggregation remain to be differentiated. Among surface architectures constructed with OPE-B and POP-B systems by zipper and layer-by-layer (LBL) assembly, photocurrents generated by OPE-B zippers exhibit the best critical thickness and fill factors. These findings confirm the existence and functional relevance of topologically matching zipper architectures. In OPE-B zippers, OPEs generate much more photocurrent than the blue NDIs. Ultrafast electron transfer from OPEs to NDIs accounts for these photocurrents, providing wavelength-controlled access to rod–stack charge separation, and thus to formal supramolecular n/p-heterojunctions (SHJs). NDI excitation is not followed by the complementary hole transfer to the OPE rod. Scaffolds with higher HOMOs will be needed to integrate blue NDIs into SHJ photosystems.
- Published
- 2010
93. Cover Picture: Zipper Assembly of Vectorial Rigid-Rod π-Stack Architectures with Red and Blue Naphthalenediimides: Toward Supramolecular Cascade n/p-Heterojunctions (Angew. Chem. Int. Ed. 20/2008)
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Adam L. Sisson, Naomi Sakai, Natalie Banerji, Alexandre Fürstenberg, Eric Vauthey, and Stefan Matile
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General Chemistry ,Catalysis - Published
- 2008
94. Titelbild: Zipper Assembly of Vectorial Rigid-Rod π-Stack Architectures with Red and Blue Naphthalenediimides: Toward Supramolecular Cascade n/p-Heterojunctions (Angew. Chem. 20/2008)
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Stefan Matile, Natalie Banerji, Naomi Sakai, Eric Vauthey, Alexandre Fürstenberg, and Adam L. Sisson
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Zipper ,Stack (abstract data type) ,Cascade ,Chemistry ,Supramolecular chemistry ,Heterojunction ,Nanotechnology ,General Medicine ,Rigid rod ,Artificial photosynthesis - Published
- 2008
95. Tuning the Excited-State Dynamics of GFP-Inspired Imidazolone Derivatives.
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Irina Petkova, Georgi Dobrikov, Natalie Banerji, Guillaume Duvanel, Robert Perez, Vladimir Dimitrov, Peter Nikolov, and Eric Vauthey
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- 2010
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96. Excited-State Dynamics of Hybrid Multichromophoric Systems: Toward an Excitation Wavelength Control of the Charge Separation Pathways.
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Natalie Banerji, Guillaume Duvanel, Alejandro Perez-Velasco, Santanu Maity, Naomi Sakai, Stefan Matile, and Eric Vauthey
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- *
EXCITED state chemistry , *PHOTOCHEMISTRY , *LASER spectroscopy , *OXIDATION-reduction reaction , *SYMMETRY breaking , *REARRANGEMENTS (Chemistry) - Abstract
The photophysical properties of two hybrid multichromophoric systems consisting of an oligophenylethynyl (OPE) scaffold decorated by 10 red or blue naphthalene diimides (NDIs) have been investigated using femtosecond spectroscopy. Ultrafast charge separation was observed with both red and blue systems. However, the nature of the charge-separated state and its lifetime were found to differ substantially. For the red system, electron transfer occurs from the OPE scaffold to an NDI unit, independently of whether the OPE or an NDI is initially excited. However, charge separation upon OPE excitation is about 10 times faster, and takes place with a 100 fs time constant. The average lifetime of the ensuing charge-separated state amounts to about 650 ps. Charge separation in the blue system depends on which of the OPE scaffold or an NDI is excited. In the first case, an electron is transferred from the OPE to an NDI and the hole subsequently shifts to another NDI unit, whereas in the second case symmetry-breaking charge separation between two NDI units occurs. Although the charges are located on two NDIs in both cases, different recombination dynamics are observed. This is explained by the location of the ionic NDI moieties that depends on the charge separation pathway, hence on the excitation wavelength. The very different dynamics observed with red and blue systems can be accounted for by the oxidation potentials of the respective NDIs that are higher and lower than that of the OPE scaffold. Because of this, the relative energies of the two charge-separated states (hole on the OPE or an NDI) are inverted. [ABSTRACT FROM AUTHOR]
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- 2009
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97. Intramolecular Charge-Transfer Dynamics in Covalently Linked Perylene−Dimethylaniline and Cyanoperylene−Dimethylaniline.
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Natalie Banerji, Gonzalo Angulo, Igor Barabanov, and Eric Vauthey
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- *
CHARGE transfer , *PERYLENE , *DIMETHYLANILINE , *ELECTRON donor-acceptor complexes - Abstract
The excited-state dynamics of covalently linked electron donor−acceptor systems consisting of N, N-dimethylaniline (DMA) as electron donor and either perylene (Pe) or cyanoperylene (CNPe) as acceptor has been investigated in a large variety of solvents, including a room-temperature ionic liquid, by using femtosecond time-resolved fluorescence and absorption spectroscopy. The negligibly small solvent dependence of the absorption spectrum of both compounds and the strong solvatochromism of the fluorescence are interpreted by a model where optical excitation results in the population of a locally excited state (LES) and emission takes place from a charge-separated state (CSS). This interpretation is supported by the fluorescence up-conversion and the transient absorption measurements that reveal substantial spectral dynamics in polar solvents only, occurring on time scales going from a few hundreds of femtoseconds in acetonitrile to several tens of picoseconds in the ionic liquid. The early transient absorption spectra are similar to those found in nonpolar solvents and are ascribed to the LES absorption. The late spectra due to CSS absorption show bands that are red-shifted relative to those of the radical anion of the acceptor moiety by an amount that depends on solvent polarity, pointing to partial charge separation. Global analysis of the time-resolved data indicates that the charge separation dynamics in PeDMA is essentially solvent controlled, whereas that in CNPeDMA is faster than diffusive solvation, this difference being accounted for by a larger driving force for charge separation in the latter. On the other hand, the CSS lifetime of PeDMA is of the order of a few nanoseconds independently of the solvent, whereas that of CNPeDMA decreases with increasing solvent polarity from a few nanoseconds to a few hundreds of picoseconds. Comparison of these results with previously published data on the fluorescence quenching of Pe and CNPe in pure DMA shows that the charge separation and the ensuing charge recombination occur on similar time scales independently of whether these processes are intra- or intermolecular. [ABSTRACT FROM AUTHOR]
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- 2008
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98. Ultrafast Photoinduced Charge Separation in Naphthalene Diimide Based Multichromophoric Systems in Liquid Solutions and in a Lipid Membrane.
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Natalie Banerji, Alexandre Fürstenberg, Sheshanath Bhosale, Adam L. Sisson, Naomi Sakai, Stefan Matile, and Eric Vauthey
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- *
BILAYER lipid membranes , *SOLUTION (Chemistry) , *IMIDES , *TIME-resolved spectroscopy , *TETRAMERS (Oligomers) , *FLUORESCENCE , *MOLECULAR self-assembly , *CHEMICAL bonds - Abstract
The photophysical properties of multichromophoric systems consisting of eight red or blue naphthalene diimides (NDIs) covalently attached to a p-octiphenyl scaffold, as well as a blue bichromophoric system with a biphenyl scaffold, have been investigated in detail using femtosecond time-resolved spectroscopy. The blue octachromophoric systems have been recently shown to self-assemble as supramolecular tetramers in lipid bilayer membranes and to enable generation of a transmembrane proton gradient upon photoexcitation ( Bhosale, S.; Sisson, A. L.; Talukdar, P.; Fürstenberg, A.; Banerji, N.; Vauthey, E.; Bollot, G.; Mareda, J.; Röger, C.; Würthner, F.; Sakai, N.; Matile, S.Science2006, 313, 84). A strong reduction of the fluorescence quantum yield was observed when going from the single NDI units to the multichromophoric systems in methanol, the effect being even stronger in a vesicular lipid membrane. Fluorescence up-conversion measurements reveal ultrafast self-quenching in the multichromophoric systems, whereas the formation of the NDI radical anion, evidenced by transient absorption measurements, points to the occurrence of photoinduced charge separation. The location of the positive charge could not be established unambiguously from the transient absorption measurements, but energetic considerations indicate that charge separation should occur between two NDI units in the blue systems, whereas both an NDI unit and the p-octiphenyl scaffold could act as electron donor in the red system. The lifetime of the charge-separated state was found to increase from 22 to 45 ps by going from the bi- to the octachromophoric blue systems in methanol, while a 400 ps decay component was observed in the lipid membrane. This lifetime lengthening is explained in terms of charge migration that is most efficient when the octachromophoric systems are assembled as supramolecular tetramers in the lipid membrane. Furthermore, the average charge-separated state lifetime of the red system in methanol is even larger and amounts to 750 ps. This effect cannot be simply explained in terms of Marcus inverted regime as the driving force for charge recombination in the red system is only slightly larger than in the blue one. A better spatial separation of the charges in the red system stemming from the localization of the hole on the p-octiphenyl scaffold could additionally contribute to the slowing down of charge recombination. [ABSTRACT FROM AUTHOR]
- Published
- 2008
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99. Nanocomposite of nickel oxide nanoparticles and polyethylene oxide as printable hole transport layer for organic solar cells
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Artem Levitsky, Natalie Stingelin, Wolfgang Kowalsky, Gitti L. Frey, Natalie Banerji, Giovanni Maria Matrone, Eric Mankel, Gerardo Hernandez-Sosa, Patrick Reiser, Stefan Schlisske, Marta Ruscello, Eleni Sachs, Nikolaos Droseros, and Tanmoy Sarkar
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Nanocomposite ,Fabrication ,Organic solar cell ,Renewable Energy, Sustainability and the Environment ,Nickel oxide ,Energy Engineering and Power Technology ,Nanoparticle ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,7. Clean energy ,Polymer solar cell ,0104 chemical sciences ,Active layer ,Fuel Technology ,Chemical engineering ,540 Chemistry ,570 Life sciences ,biology ,ddc:620 ,0210 nano-technology ,Engineering & allied operations ,Deposition (law) - Abstract
We focused on the low-temperature fabrication (∼100 °C) of nanoparticle-based NiOx hole transport layers for organic solar cells. We used high molecular weight polyethylene oxide (PEO) as a sacrificial additive for the processing of NiOx nanoparticle (NP) dispersions which is removed from the film by oxygen plasma prior to the active layer deposition. Through comprehensive characterization by optical, electrical and scanning probe techniques we show that an optimal NiOx : PEO ratio allows to disperse the NPs, hindering their aggregation and maximizing device performance. Finally, we demonstrate the practical relevance of our approach by inkjet printing the NiOx:PEO blends to produce hole transport layers (HTLs) for P3HT:PCBM bulk heterojunction solar cells with comparable efficiencies to devices produced with high-temperature precursor-based approaches. The utilization of P3HT:PCBM as active layer material is meant to offer an optimum standard for the introduction of the presented HTL processing approach and its applicability to a wider range of hybrid systems and multilayer optoelectronic devices.
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100. Sensitization of fullerenes by covalent attachment of a diketopyrrolopyrrole chromophore
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Eneida S. Chesnut, Mingfeng Wang, Jian Fan, Fred Wudl, Natalie Banerji, and Jacques-E. Moser
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Materials science ,Fullerene ,Quenching (fluorescence) ,Absorption spectroscopy ,Organic solar cell ,Copolymers ,Photoinduced Electron-Transfer ,Quantum yield ,General Chemistry ,Bulk ,Chromophore ,Photochemistry ,Photoinduced electron transfer ,Fluorescence spectroscopy ,Pendant Fullerenes ,Materials Chemistry ,Low-Band-Gap ,Organic Photovoltaics ,Double-Cable Polymers ,Donor ,Polymer Solar-Cells ,Photophysical Properties - Abstract
In an effort to develop new materials for organic solar cell applications, we have synthesized triads of 3,6-dithien-2-yl-2,5-dialkylpyrrolo[3,4-c]pyrrole-1,4-dione (DTDPP) covalently linked at the nitrogen positions to two [6,6]-phenyl-C61-butyric acid ester (PCB) units via alkyl chains of different lengths. We present here the excited-state properties of the compounds in solution, as investigated by (time-resolved) spectroscopy. The absorption spectra of the triads are the composite of the ones recorded with the separate fullerene and DTDPP parent molecules, indicating weak electronic coupling between the sub-units. However, the fluorescence quantum yield drops from 74% in pure DTDPP to
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