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.

“Fast” and “Slow” Metastable Defects in a-Si:H

1993 ◽  
Vol 297 ◽  
Author(s):  
Liyou Yang ◽  
Liang-Fan Chen
Keyword(s):  
Rate Equation ◽  
Defect Density ◽  
Convincing Evidence ◽  
Experimental Results ◽  
Component Model ◽  
Rate Equations ◽  
Defect States ◽  
Defect Generation ◽  
Two Component ◽  
Different Characteristics

A two-step light soaking experiment at high and low intensities provided convincing evidence that defect generation and annealing in a-Si:H are controlled by defect states of different characteristics. We point out that the total defect density by itself cannot uniquely determine the state of material or be described by a single rate equation, even though it might be the only quantity that is experimentally measurable. A system of rate equations for all defect components, therefore, must be established in order to accurately describe the defect kinetics. A simple two-component model in which defects are categorized as “fast” or “slow” is shown to be adequate to explain a variety of experimental results in a consistent fashion.

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.

Explanation of Light-Enhanced Annealing of Defects in Amorphous Silicon

1994 ◽  
Vol 336 ◽  
Author(s):  
David Redfield ◽  
Richard Bube
Keyword(s):  
Light Intensity ◽  
Amorphous Silicon ◽  
Rate Equation ◽  
Experimental Test ◽  
Stretched Exponential ◽  
Defect Generation ◽  
Recovery Processes ◽  
Usual Rate ◽  
Stretched Exponentials

ABSTRACTSeveral recent measurements have shown that annealing of metastable defects in a- Si:H can be accelerated by the presence of light. This is the opposite of the usual light-induced defect generation, and no existing rate equation explains it while maintaining the necessary symmetry of generation and recovery processes, and consistency with the stretched-exponential transients that best describe observed generation and anneal behavior. This paper shows that this light-enhanced annealing (LEA) can be explained readily by the usual rate equation leading to stretched exponentials with no other terms by allowing a variation of coefficients with temperature or light intensity. This equation then leads to good simulations of observed LEA. Interpretation of these results in terms of distributional changes is presented, and an experimental test is proposed.

Characterization of the defect density states in MoOx for c-Si solar cell applications

2021 ◽  
pp. 108135
Author(s):  
D. Scirè ◽  
R. Macaluso ◽  
M. Mosca ◽  
S. Mirabella ◽  
A. Gulino ◽  
...  
Keyword(s):  
Solar Cell ◽  
Defect Density ◽  
Si Solar Cell

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.

Hydrogenated Amorphous Silicon Germanium Alloy for Stable Solar Cells

1994 ◽  
Vol 336 ◽  
Author(s):  
A. Terakawa ◽  
M. Shima ◽  
K. Sayama ◽  
H. Tarui ◽  
H. Nishiwaki ◽  
...  
Keyword(s):  
Solar Cell ◽  
Conversion Efficiency ◽  
Silicon Germanium ◽  
Defect Density ◽  
Characteristic Energy ◽  
Solar Cell Performance ◽  
Germanium Content ◽  
Junction Solar Cell ◽  
Degradation Ratio ◽  
Double Junction

ABSTRACTThe film properties and solar cell performance of a-SiGe:H samples with the same optical gap and different combinations of hydrogen content (CH) and germanium content (CGe) have been compared. The optimum composition for the initial properties, such as the tail characteristic energy, defect density and conversion efficiency of the solar cell, was determined, and the differences could be explained by the difference in H bonding configuration. The degradation ratio of the conversion efficiency becomes larger in higher CH samples. This suggests that hydrogen or Si-H2 participates in light-induced degradation. As a result, the optimum CH for an efficient solar cell is believed to shift to the lower CH region after light soaking. Based on these findings, the stabilized conversion efficiency of 3.3% under red light (γ>650nm) for an a-SiGe:H single-junction solar cell (1cm2) and 10.6% under lsun light for an a-Si/a-SiGe double-junction stacked solar cell (1cm2) have been achieved. The degradation ratio is only 8.6% for the double-junction solar cell.

scholarly journals Numerical Design of Ultrathin Hydrogenated Amorphous Silicon-Based Solar Cell

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
F. X. Abomo Abega ◽  
A. Teyou Ngoupo ◽  
J. M. B. Ndjaka
Keyword(s):  
Solar Cells ◽  
Solar Cell ◽  
Amorphous Silicon ◽  
Buffer Layer ◽  
Defect Density ◽  
Hydrogenated Amorphous Silicon ◽  
Theoretical Work ◽  
Silicon Based ◽  
The Impact ◽  
Hydrogenated Amorphous

Numerical modelling is used to confirm experimental and theoretical work. The aim of this work is to present how to simulate ultrathin hydrogenated amorphous silicon- (a-Si:H-) based solar cells with a ITO BRL in their architectures. The results obtained in this study come from SCAPS-1D software. In the first step, the comparison between the J-V characteristics of simulation and experiment of the ultrathin a-Si:H-based solar cell is in agreement. Secondly, to explore the impact of certain properties of the solar cell, investigations focus on the study of the influence of the intrinsic layer and the buffer layer/absorber interface on the electrical parameters ( J SC , V OC , FF, and η ). The increase of the intrinsic layer thickness improves performance, while the bulk defect density of the intrinsic layer and the surface defect density of the buffer layer/ i -(a-Si:H) interface, respectively, in the ranges [109 cm-3, 1015 cm-3] and [1010 cm-2, 5 × 10 13  cm-2], do not affect the performance of the ultrathin a-Si:H-based solar cell. Analysis also shows that with approximately 1 μm thickness of the intrinsic layer, the optimum conversion efficiency is 12.71% ( J SC = 18.95   mA · c m − 2 , V OC = 0.973   V , and FF = 68.95 % ). This work presents a contribution to improving the performance of a-Si-based solar cells.

scholarly journals Influence of bulk defects in SnS absorber layer on optical and electrical properties of solar cell

2021 ◽  
Vol 2114 (1) ◽  
pp. 012044
Author(s):  
Mussab J. Ahmed ◽  
Ayed N. Saleh
Keyword(s):  
Solar Cell ◽  
Electrical Properties ◽  
Defect Density ◽  
Absorber Layer ◽  
Simulation Program ◽  
Optical And Electrical Properties ◽  
Absorption Layer ◽  
Low Concentrations ◽  
Concentration Of Impurities

Abstract In this research, the effect of bulk defect on the performance of the solar cell was studied by using the AFORS-HET simulation program. This was done by varying the density of defects including both Acceptor-like and donor-like within the SnS absorption layer. The thickness of the SnS layer was changed from 600nm to 9000nm with the change in bulk defect density in the same layer from (1E10 to 1E17 cm−3). The results showed that when the density of defects is less than 1E14cm−3, it has no effect on the performance of the solar cell, but its effect appears after this concentration, On the contrary, it is the effect of thickness, the results showed that the change in thickness at the defect density of E16cm−3 does not affect on the optical and electrical properties. Also, the results showed that the effect of defects is greatest at low concentrations of Na impurities, and this effect begins to decrease with increasing the concentration of impurities.

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