Improving Light Utilization

As already mentioned in Sects. 6.3.1.2 and 8.2.3, ZnO can be used as an intermediate reflector in a-Si H/ j,c-Si H tandem solar cells between top and bottom cell to increase the current in the thin amorphous silicon top cell [14,15]. As a result, the thickness of the a-Si H top cell can be reduced to improve the stability of the cell upon light induced degradation. Recent progress has even lead to improved light utilization and higher short circuit current density by an optimized intermediate reflector [16]. However, this intermediate reflector might consist of another material than ZnO. 

Polacolor. The first instant color film, Polacolot, was introduced by Polaroid Corporation in 1963. Polacolot was replaced in 1975 by Polacolot 2, a film with improved light stabiUty, which utilizes the metallized dye developers shown in Eigute 4. An extended range version, Polacolot ER, introduced in 1980, utilizes the cyan and yeUow metallized dye developers together with a magenta dye developer that incorporates a xanthene dye having reduced blue absorption (see Eig. 5). 

Degen J, Uebele A, Retze A, et al A novel airlift photobioreactor with baffles for improved hght utilization through the flashing light effect, J Biotechnol 92 89-94, 2001. 

In the attenuated total reflection (ATR) method, surface plasmon polaritons (SPPs) are resonantly excited on surface of metal thin films by the incident light, and remarkably strong absorption of the incident light occurs due to the resonantly excited SPPs[5,6]. Therefore, photoelectric effects in the cells are expected to be improved by utilizing the ATR method exciting the SPPs[7,8]. 

No less imagination has been directed to the design of photosensitizers for photocrosslinkable polymers, with the major objective of extending their spectral response as well as improving the efficiency of absorbed light utilization (sensitivity). 

Other Plastics Uses. The plasticizer range alcohols have a number of other uses in plastics hexanol and 2-ethylhexanol are used as part of the catalyst system in the polymerization of acrylates, ethylene, and propylene (55) the peroxydicarbonate of 2-ethylhexanol is utilized as a polymerization initiator for vinyl chloride various trialkyl phosphites find usage as heat and light stabHizers for plastics organotin derivatives are used as heat stabHizers for PVC octanol improves the compatibHity of calcium carbonate filler in various plastics 2-ethylhexanol is used to make expanded polystyrene beads (56) and acrylate esters serve as pressure sensitive adhesives. 

Polyesters are another important class of polyols. There are many polyester types used, so a generic structure is shown in Scheme 4.4. They are often based on adipic acid and either ethylene glycol (ethylene adipates) or 1,4-butanediol (butylene adipates). Polyesters, because of the polar carbonyl groups, contribute more to intermolecular forces, and physical properties such as tear and impact resistance are often improved by using them. They are also utilized for their solvent and acid resistance and light stability. Relatively poor hydrolytic stability is... 

A large amount of biocatalyst is usually required to reduce a considerable amount of substrate (the b/s for baker s yeast is about 50-350). On the contrary, a low b/s ratio (2.6-0.5) could be achieved using the cyanobacteria. The improvement in the b s ratio is caused by the fact that the cyanobacterium can utilize the power of light effectively to reduce the substrate. 

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