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Akimov, Yu.K.

doi:10.1023/a:1024401803057

Cited by 197 publications

(45 citation statements)

References 97 publications

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“…The porosity of aerogels is known to be controlled by the concentration of the sol and can be over 99% porous. [16,17] The aerogel films used in this study were not optimized for use in DSSCs; conditions were chosen, however, in order to make highly porous structures (>90%) in order to leave enough volume for growth of sufficiently thick ZnO layers without completely filling the aerogel pores. In addition, films approximately 25 mm thick were prepared for use as templates for the photoelectrodes described below.…”

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confidence: 99%

Aerogel Templated ZnO Dye‐Sensitized Solar Cells

et al. 2008

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Dye-sensitized solar cells (DSSCs) based on nanocrystalline TiO 2 have exhibited solar energy-conversion efficiencies of over 10% and remain one of the most promising candidates for cost-effective solar energy conversion devices. [1,2] The most efficient DSSCs reported to date utilize a high surface area photoanode, which allows for good light harvesting with a moderate extinction dye, in contact with the I 3 À /I À couple which acts as a redox mediator.[3] The good performance of DSSCs is partially attributed to the slow dark reaction, i.e., electron transfer from TiO 2 to I 3 À via a potentially multielectron process. The slow dark reaction kinetics allows for excellent charge collection despite the relatively slow (millisecond) transport through the nanoparticle network.[4]The I 3 À /I À couple, however, has several disadvantages, including limitations on the open-circuit voltage related to the redox potential of the mediator species. In order to push device performance beyond its current limits, a faster redox shuttle, which requires a smaller overpotential to reduce the oxidized dye, is likely necessary, either to increase the photovoltage (provided that the dark current in not enhanced) or to allow alternate dyes with increased spectral coverage to be used. Replacing iodide/ triiodide with faster one-electron, outer-sphere redox reagents such as ferrocene, however, has resulted in significantly worse overall performance. [5,6] Although such fast redox species efficiently reduce the oxidized dye, rapid recombination between electrons in the TiO 2 and the redox shuttle results in poor electron collection. [5][6][7] Therefore, an alternate redox shuttle will concomitantly require faster charge transport through the metal oxide frameworks to allow for complete charge collection under cell operating conditions. Several interesting photoanode architectures have been fabricated with reduced dimensionality, a design feature that is expected to accelerate charge transport. Among these new architectures are hydrothermally grown ZnO nanorod arrays, ZnO nanotubes, and TiO 2 nanotubes. [8][9][10] The ZnO nanorod arrays have been shown to exhibit much faster transport than comparable ZnO nanoparticle networks. [11,12] While nanorod devices showed promising efficiencies of 1.5%, further improvement requires overcoming the technical challenge of increasing the relatively low surface area that currently limits light-harvesting.[8] Nominally one-dimensional ZnO nanotubes showed efficiencies of 1.6%, but with limited lightharvesting again a significant performance limiting factor.[9]Here we introduce a new core-shell material as a pseudo-one dimensional ZnO photoanode produced from coating templates of high aspect ratio substructures, exhibiting initial efficiencies up to 2.4% under AM 1.5 illumination when incorporated in a DSSC. Inert low density, high surface area silica aerogel films, featuring a large range of controllable thickness and porosity, are prepared as substructure templates. The aerogel templates are coated wi...

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confidence: 99%

Aerogel Templated ZnO Dye‐Sensitized Solar Cells

et al. 2008

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“…Silica-aerogel is a transparent porous material with a highly open structure which consists of nanometer scale silica particles [18][19][20][21][22]. It has been used to investigate the disorder effects on condensed phases of He [3,9,11,13,14,[22][23][24][25][26].…”

Section: Experimental Setupsmentioning

confidence: 99%

Formation of superfluid liquid pocket in aerogel and its solidification by cooling

Matsuda

Ochi

Isozaki

et al. 2013

Low Temperature Physics

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Formation of superfluid liquid pockets of 4 He surrounded by 4 He crystals were observed in an aerogel of 96% porosity. The liquid pockets did not crystallize by application of pressure but crystallized via avalanche by cooling below a particular temperature. The crystallization by cooling was also observed when crystals occupied a smaller portion of the aerogel. Driving force for the crystallization by cooling and possible mass transport process are discussed.

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“…Silica aerogel is a tenuous porous silica network of silica nanoparticles about 30 nm in size, much smaller than the wavelength of the guided light, and has a transparent optical spectral range similar to that of silica [20,21]. Because the aerogel is mostly air, its refractive index (about 1.03 at a wavelength of 633 nm) is very close to that of air.…”

Section: Glass Nanofibers For Micro-and Nano-scale Photonic Devicesmentioning

confidence: 99%