Single junction modulation

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%. 

Fig. 8.6. Aperture area efficiency of different silicon thin film solar modules (aperture area 8 x 8 cm2) as function of light exposure time. The a-Si 11/pc-Si H tandem and i< -Si H single junction solar modules on texture etched ZnO Al were prepared at the FZJ, the a-Si H/a-Si H tandem solar module was cut from an industrially produced (0.6 m2) module...

The best stabilized cell efficiencies on ZnO Al obtained at the FZJ in a PECVD reactor for 30 x 30 cm2 substrates were 8.0, 8.9, and 11.2% for a-Si H p-i-n, )LLc-Si H p-i-n, and a-Si H/)j,c-Si H tandem cells, respectively [152], The best initial efficiency for pc-Si H single junction solar cells was achieved by Mai et al., who reached 10.3% for an absorber layer thickness of 1.6 J,m, which was deposited at a high deposition rate of 11 As-1 [153], Initial aperture area module efficiencies of 10.8 and 10.6% were achieved for a-Si H/pc-Si H tandem modules with an aperture area of 8 x 8 and 26 x 26 cm2, respectively [154,155]. The efficiency of the small area module stabilized at an efficiency of 10.1% after lOOOh of light soaking as confirmed by the National Renewable Energy Laboratory (NREL, see Fig. 8.29). 

Kitazawa T, Kobayashi S, Horiuti K, Somlyo AV, Somlyo AP 1989 Receptor coupled, permeabilized smooth muscle role of the phosphatidylinositol cascade, G proteins and modulation of the contractile response to Ca2+. J Biol Chem 264 5339-5342 Lopez-Lopez JR, Shacklock PS, Balke CW, Wier WG 1995 Local calcium transients triggered by single L-type calcium channel currents in cardiac cells. Science 268 1042-1045 Marks AR, Fleischer S, Tempst P 1990 Surface topography analysis of the ryanodine receptor/ junctional channel complex based on proteolysis sensitivity mapping. J Biol Chem 265 13143-13149... 

Single molecule Cgo based transistors were also fabricated by depositing a diluted Cgo toluene solution onto a pair of gold electrodes. The whole structure was built on an insulating Si02 layer on top of a doped Si wafer that was used as the gate electrode to modulate the electrostatic potential of the Cgo molecule trapped in the middle of the junction (see Fig. 14). The observed 1-V characteristics were... 

McMahon DG, Kanpp AG, Dowling JE Horizontal cells gap junctions Single channel conductance and modulation by dopamine. Proc Natl Acad Sci USA 1989 86 7639-7643. 

Neyton J, Trautmann A Single channel curents of an intercellular junction. Nature 1985 317 331-335. Neyton J, Trautmann A Acetylcholine modulation of the conductance of intercellular junctions between... 

B.R. Takens-Kwak, H.J. Jongsma, Cardiac gap junctions three distinct single channel conductances and their modulation by phosphorylating treatments, Pfliigers Arch - Eur J Physio 422, 198-200 (1992). 

The output signal is the current through a load inductor, which is inductively coupled to the modulator. The single Josephson junction connected in series with the load acts as the signal limiter. 

It is hoped that such studies of single hemichannels will be complemented by studies of reconstituted junctional channels the double-membrane form. Development of a stable, well-characterized, and well-controlled double-membrane system is a challenging prospect. The literature on osmotic control of fusion of apposed bulged bilayers may be helpful in this regard (120, 121). Such a system would permit exploration of the forces involved in the assembly of junctional channels, which would be of interest from biophysical and cellular perspectives. For example, does the space between two membranes need to be dehydrated for hemichannels to interact (122) Do the hemichannels find each other by random interactions or does dielectric attraction (123-125) play a role Once junctional channels are formed, how reversible is the interaction between them and what forces tend to stabilize it Most important, how are the permeability, gating, and modulation of single hemichannels altered by interactions with each other in the doublemembrane form These and other considerations make the exploration of connexin channels in reconstituted systems of profound interest and promising prospects. 

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