Panchromatic

The optimal sensitizer for the dye-sensitized solar cell should be panchromatic, i.e., it should absorb visible light of all colors. Ideally, all photons at wavelengths shorter than a threshold of about 920 nm (see Section 9.16.1.1) should be harvested and converted to electric current.1,2 In addition, the sensitizer should fulfill several other demanding conditions ... 

Molecular engineering of ruthenium complexes that can act as panchromatic CT sensitizers for Ti02-based solar cells presents a challenging task as several requirements have to be fulfilled by the dye, which are very difficult to be met simultaneously. The lowest unoccupied molecular orbitals (LUMOs) and the highest occupied molecular orbitals (HOMOs) have to be maintained at levels where photo-induced electron transfer into the Ti02 conduction band and regeneration... 

A continuous flow of data falls from the sky like a fountain, into the open mouths of satellites like FUSE, Chandra and XMM. An enigmatic portrait of cosmic violence is being painted in our understanding of nature, peopled by supernovas, neutron stars, black holes and stellar corpses, telling of death and the life beyond it. For the panchromatic astronomy of the invisible, the sky is literally exploding upon our understanding. 

Pechy P, Renouard T, Zakeeruddin SM et al (2001) Engineering of efficient panchromatic sensitizers for nanocrystalline Ti02-based solar cells. J Am Chem Soc 123 1613-1624 Zhu H, Wei J, Wang K et al (2009) Applications of carbon materials in photovoltaic solar cells. Solar Energy Mater Solar Cells 93 1461-1470... 

Such dyes found early application as sensitizers in photography and many thousands of related structures have been made. Suitable dyes when added to the photographic emulsion extend the sensitivity of the silver halide from the blue and UV region towards the green, red and near IR. The sensitivity of the dyes can be balanced throughout the visible spectrum to give panchromatic emulsions. 

Figure 17.47 In parallel connected stacked cell based on the ( )/( ) couple. 1 is a transparent FTO cathode modified via chemisorption of an electroactive molecule. 2 is a conventional gold cathode. The red and the blue dyes, absorbing in complementary spectral regions, result in a panchromatic sensitization.

Molecular engineering of ruthenium complexes that can act as panchromatic charge-transfer sensitizers for TiOi-based solar cells presents a challenging task, as several requirements which are very difficult to be met simultaneously have... 

As already shown, the sensitized spectra follow the dye absorption. Most of the dyes have sufficiently narrow absorption bands. This does not permit us to obtain the panchromatic sensitivity in the sufficiently broad spectral range. It was proposed to use the polymers with conjugated bonds as sensitizers [21]. The broad diffuse absorption spectra are inherent to such compounds. One can expect higher thermal stability from such sensitizers. In addition the application of binder may be omitted from the preparation of the photosensitive layers, for example, in electrophotography. Polymers with triple bonds, polyphenylenes and polyoxiphenylenes were used as sensitizers [10, 14, 278-280]. The typical results are shown in Fig. 47. The main rules for photoconductivity sensitized by polymers were the same as for the dyes. Optimum sensitization was obtained at the concentration of the sensitizer of 10 1-10-2 g/cm3 relative to the polymeric photoconductor weight. 

A set of color-separation negatives may be prepared by photographing the subject three times on separate color-sensitive emulsions so that each is a record of one of the primary colors. A panchromatic emulsion is generally employed with a set of tricolor filters, the colors of the primaries. It is only necessary, however, to obtain the color records on separate negatives so it is also possible to use for each record any combination of color filter and emulsion sensitivity that will record one of the primary colors. A set of color-separation negatives may be made by exposing (1) each one in tmn in a camera, (2) by ihe use of a colcu camera that will expose them simultaneously, or (3) in a tripack. 

All infrared-sensitive materials must be loaded and developed in total darkness, as safelight screens, even those for panchromatic films and plates, transmit the infrared freely. 

In Dr. M. Gratzel s plenary lecture at IPS-2000,103 he presented the following research topics to improve DSC. 1) Mastering the interfaces, electron transfer dynamics, control of dark current. 2) Charge transport in nanocrystalline films. 3) Panchromatic sensitizers, dye cocktail, quantum dot charge injection. 4) Light management, mixed metal oxide films, core-shell metal oxide films. 5) New... 

Panchromatic sensitization of vinyl addition polymerization requires the presence of suitable dyes as primary absorbers of radiation. In 1949 Bamford and Dewar (5) reported that styrene could be polymerized by irradiation of a variety of dyes. It was later shown by Koizumi, Watanabe, and Kuroda (6) that these reactions, and others uncovered by the Japanese group, were the result of photoinduced decomposition of the dyes rather than a true sensitization process. 

In addition to different types of emulsions, there are different types of film. These include panchromatic films, which are sensitive to all colors of visible light to varying degrees (these include all those films mentioned in the previous section) orthochromatic films, which are primarily blue-sensitive infrared films, which record in the infrared or near-infrared spectrum document films, which are extremely high in contrast exhibiting little or no mid-tones unless... 

As panchromatic film choices have narrowed, so too have choices in alternative films. Current orthochromatic films include Adox 25 ORT and Rollei Ortho 25 . Infrared films... 

Almost any panchromatic film made today can be pushed one stop with little or no discernible loss in quality. For example, Kodak Tri-X can easily be pushed to El 800 and Ilford Delta 3200 (which is closer to El 1200 than it is to ISO 3200) can easily be pushed one stop to El 2400. Try adding 25% to the normal development time for Tri-X, and 25% to 40% with other films for a one stop push. With testing and experience, you should be able to capture almost any event on film, regardless of how little ambient light is present. (See Yuette at the Coffee House on page 53 )... 

Both the transmission and reflection methods work equally well with any panchromatic film. Using either method, as many sheets of film as can be safely handled at once can be developed. When a film is fully developed it should be moved into a holding acid stop bath or running-water rinse where it can be left until the other films catch up at which time they can all... 

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