Comprehensive Kinetic of Defects in a-SI:H

1991 ◽  
Vol 219 ◽  
Author(s):  
David Redfield ◽  
Richard H. Bube
Keyword(s):  
Solar Cells ◽  
Steady State ◽  
Light Intensity ◽  
Rate Equation ◽  
Defect Density ◽  
Microscopic Models ◽  
Dx Center ◽  
Stretched Exponentials ◽  
Kinetics Of ◽  
Insight Into

ABSTRACTLThe introduction of several new principles into the analysis of transition kinetics of metastable defects in a-Si:H has produced substantially improved rate equation for the density of defects as functions of time, light intensity, and temperature. The solution of this equation is stretched exponential (SE) having properties that explain in unifying way many observations of defect properties, including generation and anneal of the defect density in homogeneous films and degradation and anneal of solar cells. Major consequences are found for both the steady-state and transient properties of the defect density and for interpretations of microscopic models of the defects. These properties are also shown to be analogous to those of metastable centers in other materials, particularly the metastable DX center in AlGaAs which offers rare insight into the microscopic origins of stretched exponentials that can be applied to a-Si:H in ways that provide new perspectives on effects of alloying and hydrogen on stability.

Annealing Kinetics of Amorphous Silicon Alloy Solar Cells Made at Various Deposition Rates

2001 ◽  
Vol 664 ◽  
Author(s):  
Baojie Yana ◽  
Jeffrey Yanga ◽  
Kenneth Lord ◽  
Subhendu Guha
Keyword(s):  
Solar Cells ◽  
Solar Cell ◽  
Amorphous Silicon ◽  
High Frequency ◽  
Room Temperature ◽  
Defect Density ◽  
Very High Frequency ◽  
Solar Cell Performance ◽  
Kinetics Of ◽  
Very High

ABSTRACTA systematic study has been made of the annealing kinetics of amorphous silicon (a-Si) alloy solar cells. The cells were deposited at various rates using H2 dilution with radio frequency (RF) and modified very high frequency (MVHF) glow discharge. In order to minimize the effect of annealing during light soaking, the solar cells were degraded under 30 suns at room temperature to quickly reach their saturated states. The samples were then annealed at an elevated temperature. The J-V characteristics were recorded as a function of annealing time. The correlation of solar cell performance and defect density in the intrinsic layer was obtained by computer simulation. Finally, the annealing activation energy distribution (Ea) was deduced by fitting the experimental data to a theoretical model. The results show that the RF low rate solar cell with high H2 dilution has the lowest Ea and the narrowest distribution, while the RF cell with no H2 dilution has the highest Ea and the broadest distribution. The MVHF cell made at 8Å/s withhigh H2 dilution shows a lower Ea and a narrower distribution than the RF cell made at 3 Å/s, despite the higher rate. We conclude that different annealing kinetics plays an important role in determining the stabilized performance of a-Si alloy solar cells.

Kinetics of Light-Induced Degradation of a-Si:H Solar Cells Compared to I-Layer Films

1992 ◽  
Vol 258 ◽  
Author(s):  
X.R. Li ◽  
S. Wagner ◽  
M. Bennett ◽  
S. Fonash
Keyword(s):  
Solar Cells ◽  
Defect Density ◽  
Monochromatic Light ◽  
Performance Parameters ◽  
Electron Hole ◽  
Different Temperatures ◽  
Electron Hole Pair ◽  
Pair Generation ◽  
Kinetics Of ◽  
High Intensity Light

ABSTRACTWe report the CPM defect density of a-Si:H material and the performance characteristics of pin solar cells during high-intensity light-soaking. In one group of experiments we compared the effects of soaking with monochromatic light from a Kr+ laser to white light from a Xe arc lamp. The effects are identical for the same electron-hole pair generation rate. In a second group of experiments we light-soaked at the two different temperatures of 50°C and 90°C. At 90°C the defect density saturates at a lower value than at 50°C, and correspondingly the cell performance parameters saturate at higher values.

Defect Saturation in a-SiGe:H(F) Alloys

1992 ◽  
Vol 258 ◽  
Author(s):  
N.W. Wang ◽  
P.A. Morin ◽  
V. Chu ◽  
S. Wagner
Keyword(s):  
Steady State ◽  
Low Temperature ◽  
Light Intensity ◽  
Carrier Concentration ◽  
Thermal Annealing ◽  
Defect Density ◽  
High Light Intensity ◽  
High Light ◽  
The Other ◽  
Induced Defects

ABSTRACTIt is a question as yet unresolved whether the density of light-induced defects in a-Si:H reaches a saturated value that cannot fundamentally be exceeded, or whether the defect density is in all conditions a steady-state value that reflects carrier concentration and temperature. In our experiments on a-Si:H we have observed defect saturation at low temperature and high light intensity; on the other hand, data exhibiting no saturation have also been published. To learn more about this question we have carried out saturation experiments on a-SiGe:H(F) alloys. These alloys have lower defect freeze-in temperatures than a-Si:H and, presumably, lower annealing energies. Therefore, saturation should be more difficult to achieve in the alloys than in a-Si:H.We have studied saturation for a-SiGe:H(F) samples to temperatures above the onset of thermal annealing and have observed that its behavior is similar to that seen in a-Si:H.

Thermal and Optical Stretched Exponentials in Defect Kinetics in a-Si:H

1993 ◽  
Vol 297 ◽  
Author(s):  
David Redfield ◽  
Richard Bube
Keyword(s):  
Solar Cell ◽  
Rate Equation ◽  
Defect Density ◽  
Dispersion Parameter ◽  
Thermally Induced ◽  
Defect Generation ◽  
Weak Light ◽  
New Equation ◽  
Stretched Exponentials ◽  
Dispersive Character

Dispersive description of defect generation in a-Si:H that leads to stretched-exponential transients is extended by relaxing the assumption that light-induced processes and thermally induced processes have the same dispersive character. This is done by separating the rate equation for the defect density into two parts, one thermal and one optical, each with its own dispersion parameter. The solutions of this new equation — which must be obtained numerically — generally have two distinct parts: there may be a two-part rise or a peak, depending on the relative values of the two stretch parameters. Using this formulation we have readily simulated the recently observed peak in relaxation of a previously heavily degraded solar cell while exposed to a weak light. We find no way to explain other reports in similar two-part experiments that relaxation is faster under weak excitation than without.

Steady-state kinetics of thyroid peroxidase. evidence for a high degree rate equation using the f statistic

1983 ◽  
Vol 15 (9) ◽  
pp. 1195-1200
Author(s):  
Francisco Solano-Muñoz ◽  
JoséL. Iborra ◽  
JoséA. Lozano ◽  
William G. Bardsley
Keyword(s):  
Steady State ◽  
Rate Equation ◽  
Thyroid Peroxidase ◽  
Steady State Kinetics ◽  
High Degree ◽  
Kinetics Of

The Kinetics of the Catalyzed Reaction between Two Substrates in a Special Case

1975 ◽  
Vol 53 (5) ◽  
pp. 644-647
Author(s):  
Jaroslav Rybicky
Keyword(s):  
Steady State ◽  
Relative Error ◽  
Rate Equation ◽  
Practical Utility ◽  
Sum Of Products ◽  
Kinetics Of ◽  
Special Case ◽  
Fold Excess

The kinetics of the catalyzed reaction between two substrates is dealt with for the special case in which the product associated with the catalyst cannot be distinguished from the product dissociated from the catalyst. The rate equation in which the yield is a sum of products both associated with and dissociated from the catalyst is derived and its applicability is assessed with respect to the kinetic and concentration conditions. It was found that under steady-state conditions and fast preequilibrium condition a twenty-fold excess of the substrates over the catalyst is enough for the yield of reaction to be represented by the equation derived with less than 1% relative error, and even for a five-fold excess the equation remains a fairly good approximation. Under such conditions the rate equation can find practical utility.

Linkage of Efficiency and Stability of a-Si Solar cells

1989 ◽  
Vol 149 ◽  
Author(s):  
David Redfield ◽  
Richard H. Bube
Keyword(s):  
Solar Cells ◽  
Steady State ◽  
Separate Species ◽  
Defect Centers ◽  
Si Solar Cells ◽  
The Stability ◽  
Kinetics Of

ABSTRACTBy combining the steady-state and transient behaviors of a recently generalized analysis of the kinetics of metastable defects in good amorphous Si:H, it is shown that no treatment can remove all metastable defects. There is always a significant remnant that is proposed to be the observed built-in defects, which are then not a separate species, distinct from the metastable defects. This remnant is due to vibrational breaking of weak bonds in latent defect centers, and cannot be due to recombination of thermally excited carriers. If the stability can be improved by reducing the number of these latent defect centers, this will also reduce the density of built-in defects that control the initial efficiency. Furthermore, there are good reasons to believe that the source of these defects is extrinsic to a-Si:H, so that improvement in both properties may be achievable.

A COMPARISON BETWEEN THE INITIAL RATE EXPRESSIONS OBTAINED UNDER STRICT CONDITIONS AND THE RAPID EQUILIBRIUM ASSUMPTION USING, AS EXAMPLE, A FOUR SUBSTRATE ENZYME REACTION

2011 ◽  
Vol 10 (05) ◽  
pp. 659-678
Author(s):  
J. M. YAGO ◽  
C. GARRIDO-DEL SOLO ◽  
M. GARCIA-MORENO ◽  
R. VARON ◽  
F. GARCIA-SEVILLA ◽  
...  
Keyword(s):  
Steady State ◽  
Rate Equation ◽  
Initial Rate ◽  
Enzyme Reaction ◽  
Rate Equations ◽  
Steady State Rate ◽  
State Rate ◽  
Rapid Equilibrium ◽  
Kinetics Of ◽  
Substrate Concentrations

The software WinStes, developed by our group, is used to derive the strict steady-state initial rate equation of the reaction mechanism of CTP:sn-glycerol-3-phosphate cytidylyltransferase [EC 2.7.7.39] from Bacillus subtilis. This enzyme catalyzes a reaction with two substrates and operates by a random ordered binding mechanism with two molecules of each substrate. The accuracy of the steady-state rate equation derived is checked by comparing the rate values it provides with those obtained from the simulated progress curves. To analyze the kinetics of this enzyme using the strict steady-state initial rate equation, several curves for different substrate concentrations and different rate constants are generated. A comparison of these curves with the curves obtained from the rapid equilibrium initial rate equation, with different substrate concentration values, serves to analyze how the strict steady-state rate equation values are closer to those of rapid equilibrium rate equations when rapid equilibrium conditions are fulfilled.

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