Solar energy organic dyes

Photochromic dyes, 20 516 Photochromic glass silver in, 22 658, 686 as a solar energy material, 23 5 Photochromic lenses, 6 588, 601-602 Photochromic materials, 6 587-606 inorganic, 6 589-592 organic, 6 592-601 polyoxometalates, 6 591-592 silver halide-containing glasses, 6 589-590... 

The prototypical photochemical system for CO2 reduction contains a photosensitizer (or photocatalyst) to capture the photon energy, an electron relay catalyst (that might be the same species as the photosensitizer) to couple the photon energy to the chemical reduction, an oxidizable species to complete the redox cycle and CO2 as the substrate. Figure 1 shows a cartoon of the photochemical CO2 reduction system. An effective photocatalyst must absorb a significant part of the solar spectrum, have a long-lived excited state and promote the activation of small molecules. Both organic dyes and transition metal complexes have been used as photocatalysts for CO2 reduction. In this chapter, CO2 reduction systems mediated by cobalt and nickel macrocycles and rhenium complexes will be discussed. 

The absorption, emission, and redox properties of squaraines make them highly suited for applications as photosensitizers. In view of this, the early studies on squaraines were focused on thin photovoltaic and semiconductor photosensitization properties [1,4,5,91-97], Champ and Shattuck [98] first demonstrated that squaraines could photogenerate electron-hole (e-h) pairs in bilayer xerographic devices. Subsequently, extensive work has been carried out on the xerographic properties of squaraines [2,24,34,47,48,99,100], and these properties have been reviewed recently [11]. In an extensive smdy on the correlation s between cell performance and molecular structure in organic photovoltaic cells, squaraines were found to have much better solar energy conversion efficiencies than a variety of other merocyanine dyes [4,5]. 

Reeves, P, Ohlhausen, R., and Sloan, D., 1992, Photocatalytic destruction of organic dyes in aqueous Ti02 suspensions using concentrated simulated and natural solar energy. Solar Energy, 48(6) 413-420. 

Schlettwein, D., and Wohrle, D. (2000) Controlled doping of organic dyes basic mechanisms and implications for their use in organic photovoltaic cells. Solar Energy Mater. Solar Cells, 63, 83-99. 

Recently a dye-sensitized solar cell has been attracting a great deal of attention for converting solar energy into electricity [52]. Since this cell uses a redox electrolyte solution, it is important to solidify the liquid in order to stabilize the cell, but the task is not easy to achieve. To overcome this problem, solidification of the organic redox electrolyte solution by molten salts and gelator [53] or by polymer film [54,55] has been achieved. We have successfully used the polysaccharide solid to solidify the electrolyte solution [56,57], as later described in Sect. 4.1. 

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