Stabilization efficiency

Amorphous Silicon. Amorphous alloys made of thin films of hydrogenated siUcon (a-Si H) are an alternative to crystalline siUcon devices. Amorphous siUcon ahoy devices have demonstrated smah-area laboratory device efficiencies above 13%, but a-Si H materials exhibit an inherent dynamic effect cahed the Staebler-Wronski effect in which electron—hole recombination, via photogeneration or junction currents, creates electricahy active defects that reduce the light-to-electricity efficiency of a-Si H devices. Quasi-steady-state efficiencies are typicahy reached outdoors after a few weeks of exposure as photoinduced defect generation is balanced by thermally activated defect annihilation. Commercial single-junction devices have initial efficiencies of ca 7.5%, photoinduced losses of ca 20 rel %, and stabilized efficiencies of ca 6%. These stabilized efficiencies are approximately half those of commercial crystalline shicon PV modules. In the future, initial module efficiencies up to 12.5% and photoinduced losses of ca 10 rel % are projected, suggesting stabilized module aperture-area efficiencies above 11%. 

The key determinants of future cost competitiveness of a-Si H PV technology are a-Si H deposition rates, module production yields, stabilized module efficiencies, production volume, and module design. Reported a-Si H deposition rates vary by more than a factor of 10, but most researchers report that the high quaUty films necessary for high stabilized efficiencies require low deposition rates often due to high hydrogen dhution of the Si (and Ge) source gases (see Semiconductors, amorphous). 

Table 2 Melt Stabilizing Efficiency of Antioxidants in PP (processed in an internal mixer at 190°C). Melt flow index (MFI) Measured at 230 C and 2.16 Kg...

Cunningham, C.C., Gorlin, J.B., Kwiatowski, D.J., Hartwig, J.H., Janmey, P.A., Byers, R., Stossel, T.P. (1992). Actin-binding protein requirement for cortical stability efficient locomotion. Science, 255,325-327. 

Surfactants are useful in formulating a wide variety of disperse systems. They are required not only during manufacture but also for maintaining an acceptable physical stability of these thermodynamically unstable systems. Besides the stabilizing efficiency, the criteria influencing the selection of surfactants for pharmaceutical or cosmetic products include safety, odor, color, and purity. 

For this purpose, stabilization efficiency was defined as 1-As/Aq, where As and Aq represent the increase in absorbance in the blue spectral region (yellowing) in the presence and absence of stabilizer, respectively. The resulting stabilization efficiencies were found to decrease substantially over relatively short exposure times (ca. 40% decrease between 10 and 25 hrs irradiation). Difference absorption spectra obtained during accelerometer exposure exhibited a new absorption band at ca. 300 nm which overlapped strongly with polymer fluorescence (required for efficient RET quenching) and weakly with polymer absorption (screening).1... 

With increasing concentration of DHB, the photoproduct forms more slowly, as evidenced by decreasing loss of fluorescence intensity (Table I, entries 1-3). Nevertheless, the concentration of photoproduct(s) and RET from the polymer to photoproduct(s) are expected to increase with time, and stabilization of the polymer will eventually depend upon the capability of the photoproduct(s) to dissipate excitation energy imparted in the RET process. The observed decrease in stabilization efficiency by DHB (based on film discoloration) with exposure time in an accelerometer indicates that DHB is more effective than the photoproduct(s) in dissipating the light energy. Similar spectroscopic studies on polystyrene have led to the same conclusion in this case, as well.6... 

Perylene (199) and its derivative (TBP, 200) have been widely used as blue dopant materials owing to their excellent color purity and stability. Efficient blue emitters with excellent CIE coordinates are found in biaryl compound 2,2 -bistriphenylenyl (BTP, 201) as shown in Scheme 3.62 [145]. A device of structure ITO/TPD/BTP/TPBI/Mg Ag emits bright blue emission with CIE (0.14, 0.11). A maximum brightness of 21,200 cd/m2 at 13.5 V with a maximum EQE of 4.2% (4.0 cd/A) and a power efficiency of 2.5 lm/W have been achieved. 

To keep the precipitating polymers in the dispersed state throughout the polymerization, requires steric stabilizers. This problem is classically tackled via copolymerization with fluoroalkylmethacrylates or the addition of fluorinated surfactants, both being only weak steric stabilizers. DeSimone el al. also applied a fluorinated block copolymer,9 proving the superb stabilization efficiency of such systems via a rather small particle size. One goal of the present chapter is therefore an investigation of our fluorinated block copolymers as steric stabilizers in low-cohesion-energy solvents. 

But the droplets are fragile, and must be lucidly protected. Formulating an industrial emulsion implies numerous conditions stability, efficiency, easy delivery, price,. .. This is an art, and like all forms of art it requires experience and imagination. The present book provides both. It describes basic experiments on realistic model systems. I like this matter of fact approach. For instance, instead of beginning by formal discussions on interaction energies, the book starts with methods offabrication. And, all along the text, the theoretical aspects are restricted to basic needs. 

Mahrenholtz (M5), 1958 Experimental and theoretical study of upward cocurrent gas/film flow. Data on mean film thicknesses, range of stability, efficiency of conveying liquid up wall in film, effects of physical properties of liquids. 

Figure 35. Stabilization efficiency for ion as function of square root of...

As previously shown, these templates stabilize efficiently P-tum type conformations in peptides and thus will certainly also have a significant stabilizing effect in larger loops. 

Recent experiments to determine the dimension stabilizing efficiency of water soluble fire retardent chemicals (41) showed ammonium sulfamate to be superior to phosphate salts, giving anti shrink efficiencies of 51 to 66% compared to polyethylene glycol-1000 values of 63 to 77%. Sodium silicate, because of its alkalinity, caused collapse of the wood that resulted in negative anti shrink efficiencies. Strongly alkaline systems should hence be avoided. 

Amphiphilic modification of hyperbranched polyglycerol (1) or polyethylene imine) by partial esterification or, respectively, amidation with fatty acids results in macromolecules with a nonpolar shell and a polar core. Metal nanoparticles are stabilized efficiently by these materials, because the polar moieties are responsible for adsorption to the particle surface and the nonpolar region also convey solubility in nonpolar organic solvents [17,94,95]. 

The IMT Neuchatel group achieved a stabilized efficiency of 9% (cell area 1 cm2) for a 0.25 pm-thick a-Si H p-i-n solar cell deposited on LP-CVD... 

Modules In 1993 already, the Siemens group was the first group to deposit successfully amorphous silicon (a-Si H) solar modules on ZnO layers grown by the CVD method. They reported [77] modules of 1 x 1 ft2 with an initial efficiency of 10.7% and a stabilized efficiency of 8.4%. 

Results obtained with individual a-Si H and pc-Si H solar cells are now being used to develop micromorph solar cells. Stabilized efficiency of 10.8% has so far been obtained for a micromorph tandem cell deposited on LP-CVD ZnO B front TCO, with an initial efficiency of 12.3% (see Fig. 6.57). As neither fine optimization of front ZnO surface roughness especially adapted to micromorph solar cell, nor intermediate reflector have been used to obtain this result, there is still a promising room for improvement in this field. 

In many polypropylene formulations three or more additives must be used to produce a resin with the desired stability. A wide variety of antioxidants and other stabilizers are available for this purpose. The choice of antioxidant for a given application is determined by compatibility, stabilizing efficiency, color, odor, toxicity, and cost (15). 

Figures 6, 7, and 8 show the stabilizing efficiency of the combinations consisting of the above absorbers and the antioxidant 2,4,6-tri-fert-butyl-phenol, on Fade-ometer exposure. The total additive concentration in each polystyrene sample was 0.25%. The data show that the rate of discoloration of the polymer was inhibited to a greater extent with the ultraviolet absorber-antioxidant combinations than with the absorber alone. Only a small amount (0.075%) of the antioxidant was required for increased effectiveness of the combination.

Similarly, the thiol-ended transurf 27 shows higher stabilizing efficiency than PVP in the dispersion polymerization of styrene and MMA in water-ethanol [156]. 

Determination of extractability of stabilizers should be a substantial part of the rating of stabilizer efficiency where leaching is a common deterioration effect or where legislation requires quantitative data dealing with extractability of stabilizers from packaging materials by food simulants. 

Various oligomeric condensates are formed from phenolic and aromatic amine AO and AOZ as a consequence of interactions of these reactive stabilizers with oxidizing species formed in stabilized polymers, e.g. with alkylperoxyls, alkyl hydroperoxides or ozonides [15-17]. Stabilizing efficiency is preserved in some of these compounds the latter have been discussed however mostly in connection with mechanism of action of AO or AOZ [6]. 

A sulfur moiety introduces a hydroperoxide deactivating effect into the stabilizer molecule. Moreover, the condensation of low molecular weight compounds with halides of sulfur represents an easy synthetic approach to the increase of the molecular weight and consequently to the improvement of the physical persistency of stabilizers. Efficient AO were prepared by this way from alkylphenols, aromatic amines or phenothiazine [21,174]. Most of them contain two active units connected with a sulfide/disulfide bridge and should be listed rather among high molecular weight stabilizers. Antioxidant 136 (n > m), prepared from pyrocatechol and... 

Some data deal with the stabilizing efficiency of polymers and copolymers bearing a stabilizing functionality. Three isomeric poly(vinylphenols) provided a better resistance to oxidation than the corresponding monomers (the o-hydroxy isomer provided the best protection). All tested poly(vinylphenols) were however slightly inferior to 2,6-di-rerr-butyl-4-methylphenol [330]. The presence of the... 

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