Sensitizer panchromatic

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... 

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.

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. 

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. 

Both phthalocyanines and squaraines are good candidates for bulk heterojunction solar cells. Recently, a supramolecular hetero-array of these functional dyes Pc-Sq-Pc (compound 52) has been reported for the first time, which exhibits a large coverage of the solar spectrum from 250 to 850 nm [51]. This axially held assembly serves as a robust panchromatic sensitizer. Upon excitation, it forms the radical ion pair Pc+-Sq -Pc with a long lifetime of 24 2 p,s. The use of this assembly as a donor material in solution processable bulk heterojunction solar cells has also been briefly studied. 

Finally, dyes may be used in several imaging processes to extend the inherent spectral sensitivity of an imaging process to longer wavelengths, especially to visible or near infrared regions of the spectrum. These sensitization processes are industrially very important to provide panchromatic sensitivity or sensitivity to special light sources such as lasers. This review will describe those spectral sensitization processes which involve electron transfer, but will ignore those processes based on more conventional mechanisms. 

Nazeeruddin, M., et al. (2001). Engineering of efficient panchromatic sensitizers for nanocrystalline TiOj-based solar cells. /. Am. Chem. Soc. 123,1613-1624. 

Nazeeruddin M. K., Pechy P., Renouard T., Zakeeruddin S. M., Humphry-Baker R., Comte P., Liska P., Le Cevey, Costa E., Shklover V., Spiccia L., Deacon G. B., Bignozzi C. A. and Gratzel M. (2001), Engineering of efficient panchromatic sensitizers for nanocrystalline Ti02-based solar cells , J. Am. Chem. Soc. 123, 1613-1624. 

Alternatively, if the present iodide-based redox system is maintained, introducing panchromatic sensitizers or dye mixtures can boost the efficiency of cells further. To give 15% conversion efficiency, these should be designed to yield at least 24mA/cm short circuit current under full sunlight and fill factor as well as open... 

Photocurrent spectroscopy and a time-resolved variant of this method have been used to characterize hybrid thin films of crystalline ZnO modified by 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrinato zinc (TSTPPZn) and 2,9,16,23-tetrasulfo-phthalocyaninatozinc(II) (TSPcZn), which were prepared by electrochemical deposition [747]. In films containing both sensitizers, panchromatic sensitization was observed. Details of the modification procedure had considerable influence on the photoelectrochemical efficiency of the films. 

A further fundamental prerequisite is a high extinction coefficient in the visible range of the solar spectrum. The absorption spectrum has to be chosen such that either a broad band is provided by a given sensitizer or more than one sensitizer has to be used to efficiently cover the solar spectrum (panchromatic sensitization) [95-97]. 

Silvestri, F., Lopez-Duarte, L, Seitz, W., Beverina, L, Martinez-Diaz, M.V., Marks, T.J., Guldi, D.M., Pagani, G.A., and Torres, T. (2009) A squaraine-phthalocyanine ensemble towards molecular panchromatic sensitizers... 

A panchromatic sensitization as well as a considerable efficiency in photon to electron conversion can be obtained by functionalizing titania nanostructures (nanotubes as well as nanoparticles) with CdSe. In this case both chemical and electrochemical deposition leads to morphologically similar surfaces where CdSe can be observed to decorate each nanotube. As previously observed, the electrodeposition is the preferred method for obtaining a more homogeneous coating of each nanostructure, where CdSe covers almost completely the entire length of every nanotube, also occluding their mouths (Fig. 39). 

M. K. Nazeemddin, P. Pechy, M. Gratzel, Efficient panchromatic sensitization of... 

Considerable efforts have gone into the engineering of efficient panchromatic sensitizer dyes [14], An enormous number of metal-ligand and metal-free dyes have been synthesized with the objective of improving the spectral response, which ideally should extend... 

Nazeemddin MK, Pechy P, Gratzel M (1997) Efficient panchromatic sensitization of nanocrystalline Ti02 films by a black dye based on a trithiocyanato-ruthenium complex. J Chem Commun 18 1705-1706... 

Bis-imidazole photoinitiators are well-suited to photopolymer holographic films because these photoinitiators are sensitive, can be stored indefinitely, can be sensitized to all visible wavelengths, and are readily compatible with binder systems. It was the coincident development of bis-imidazole photoinitiators which catalyzed the rapid growth of photopolymer films in DuPont, holographic films in particular. The ready sensitization of bis-inudazoles has been exploited in a wide variety of holographic photopolymer films sensitized to all major visible commercial lasers, including panchromatic sensitization for the production of fiill-color... 

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