Energy transfer in condensed systems The effect of phase organization

Bacchiocchi, Corrado; Zannoni, Claudio

doi:10.1016/s0009-2614(97)00215-7

Cited by 21 publications

(23 citation statements)

References 22 publications

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“…The anisotropy of energy transfer in liquid crystals has been predicted in the past by molecular level simulations. 58,59 This property, which is very sensitive to the aspect ratio and intermolecular distances between chromophoric units, 58,60 could be exploited in designing favorable pathways for excitons in properly engineered devices. As temperature increases transport eventually becomes isotropic via the transition to the isotropic phase: the impact of temperature on the diffusion dynamics can hence be related to the different pathways excitons use to diffuse while overall the diffusion length remains unaltered.…”

Section: Energy Transport In the Condensed Phasementioning

confidence: 99%

Does supramolecular ordering influence exciton transport in conjugated systems? Insight from atomistic simulations

et al. 2011

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We have developed a theoretical platform for modelling temperature-dependent exciton transport in organic materials, using indenofluorene trimers as a case study. Our atomistic molecular dynamics simulations confirm the experimentally observed occurrence of a liquid crystalline smectic phase at room temperature and predict a phase transition to the isotropic phase between 375 and 400 K. Strikingly, the increased orientational disorder at elevated temperatures barely affects the ability of excitons to be transported over large distances, though disorder influences the directionality of the energy diffusion process. Detailed quantum-chemical calculations show that this result arises from a trade-off between reduced excitonic couplings and increased spectral overlap at high temperatures. Our results suggest that liquid crystalline oligomeric materials could be promising candidates for engineering optoelectronic devices that require stable and controlled electronic properties over a wide range of temperatures and supramolecular arrangements.

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Section: Energy Transport In the Condensed Phasementioning

confidence: 99%

Does supramolecular ordering influence exciton transport in conjugated systems? Insight from atomistic simulations

et al. 2011

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“…In addition, in a homeotropic nematic layer k ET in the direction perpendicular to the interface is considerably higher than k ET in other directions, as discussed in the literature. [40,41] The efficient exciton transfer in the direction perpendicular to the TnBuPP/TiO 2 interface makes these bilayers promising candidates for photovoltaic applications. This study shows that an efficient light-harvesting layer is realized by a homeotropic nematic molecular arrangement.…”

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confidence: 99%

Efficient Light‐Harvesting Layers of Homeotropically Aligned Porphyrin Derivatives

et al. 2006

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The dye-sensitized solar cell, based on a wide-bandgap semiconductor photosensitized with an organic dye, is an attractive low-cost alternative to conventional silicon-based solar cells.[1] Absorption of a photon by the dye results in the formation of a strongly bound electron-hole pair, also referred to as an exciton. A key feature of the dye-sensitized solar cell is that efficient exciton decay into separate charge carriers can only occur at the interface between the dye and the semiconductor, leading to injection of an electron into the conduction band of the semiconductor. [2] Since O'Regan and Grätzel reported an efficiency over 10 % for a cell based on an interpenetrating network of dye-coated nanocrystalline TiO 2 particles and a liquid electrolyte containing a iodide/ triiodide redox mediator, [3] the use of nanostructured films in photovoltaic devices has been studied extensively. Due to complications involved in the use of a liquid electrolyte, [4] there is presently great interest in the development of all-solid-state organic/inorganic solar cells. For these cells a maximum performance of 4 % has been realized so far.[5] The use of nanostructured networks avoids the necessity of long-range exciton diffusion through the dye layer. However, in such systems electron transport is hampered by trapping at surface defects.[6] The difficulties involved in electron transport can be avoided by using a bilayer configuration consisting of a bulk semiconductor and a relatively thick dye layer. In order to realize efficient charge separation in such a bilayer configuration, the distance excitons are able to cover by diffusion (exciton diffusion length) needs to be equal to or larger than the light penetration depth, which has a typical value of 50-100 nm. The exciton diffusion length in molecular organic dye layers is usually of the order of only a few nanometers, [7][8][9][10] although Nature shows that it is possible to transport excitation energy efficiently over considerably longer distances. An example is found in the photosynthetic apparatus of purple bacteria, which consists of reaction centers and two types of lightharvesting complexes: LHI and LHII. The light-harvesting complexes consist of chlorophyll and carotenoid molecules, kept in place by proteins. [11][12][13] The presence of chlorophyll molecules leads to a strong light absorption. In addition, the structure of the light-harvesting complexes provides a highly efficient pathway for exciton transport; 80-90 % of the excitons formed on light absorption are transferred to the reaction center, where charge separation occurs.[14] For a few molecular dye systems only, exciton diffusion lengths considerably longer than a few nanometers have been realized in vacuum thermal deposited layers. [15,16] However, the expensive elaborate deposition technique makes these layers commercially less attractive and could only be applied for a few dye materials. Chlorophylls and their analogues are attractive candidates for application in dye-sensitized solar cells, [17,1...

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“…[40][41][42] Several experimental and theoretical studies on polymeric systems indicate that in one-dimensional structures the orientation is also not a negligible factor; for example, the energy transfer between two dyes entangled at each end of helical DNA was dominated by the orientation. [43][44][45][46][47][48][49][50] It was also shown that the energy transfer in block polymers also depended on the directional alignments of the polymer chain, 27,50 and moreover Palman et al reported that synthetic modification of an optically active PPE polymer allowed for the generation of both polarized absorption and luminescence by subsequent global orientation of the nanostructure. 51 Contribution of geometry can also be seen in the 1-D hybrid (1-D) system essential for electronic and biological applications.…”

Section: Introductionmentioning

confidence: 99%

Control of Energy Transfer to CdTe Nanowires via Conjugated Polymer Orientation

et al. 2008

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Nanoscale organic-inorganic hybrid materials were prepared from two highly fluorescent building blocks: CdTe nanowires (NWs) as an energy acceptor, and a rigid rod-like and water soluble poly(p-phenyleneethynylene) (PPE) as a donor. The PPE was covalently bonded to the CdTe by traditional amide chemistry. Two different orientations, parallel and perpendicular, of PPE to CdTe NW were achieved by manipulating the density of PPE at the NW surface through controlling the molar ratio of PPE and the NW during the chemical tethering. Strong dependence of fluorescence resonance energy transfer (FRET) on the orientation was observed. While efficient FRET was observed when the orientation of the donor PPE and the acceptor CdTe NW is parallel, essentially no FRET was observed from the perpendicularly oriented PPE-tethered CdTe NW system. Optical and transmission electron microscopy experiments as well as Monte Carlo simulation consistently suggest that entropy change during the tethering is a crucial factor for the determination of the orientation of PPE at the NW surface.

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Energy transfer in condensed systems The effect of phase organization

Cited by 21 publications

References 22 publications

Does supramolecular ordering influence exciton transport in conjugated systems? Insight from atomistic simulations

Does supramolecular ordering influence exciton transport in conjugated systems? Insight from atomistic simulations

Efficient Light‐Harvesting Layers of Homeotropically Aligned Porphyrin Derivatives

Control of Energy Transfer to CdTe Nanowires via Conjugated Polymer Orientation

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