Light Induced Changes in PIN Solar Cells: Beyond the Staebler-Wronski Effect

2012 ◽  
Vol 1426 ◽  
pp. 57-62
Author(s):  
Ka-Hyun Kim ◽  
Erik V. Johnson ◽  
Samir Kasouit ◽  
Pere Roca i Cabarrocas
Keyword(s):  
Solar Cells ◽  
Structural Changes ◽  
Hydrogen Diffusion ◽  
Degradation Kinetics ◽  
Degradation Mechanism ◽  
Interface Delamination ◽  
Absorbing Layer ◽  
Staebler Wronski Effect ◽  
Induced Changes ◽  
Hydrogenated Amorphous

ABSTRACTHydrogenated polymorphous silicon (pm-Si:H) is one of the most promising candidates for a stable top cell material in multi-junction thin film solar cells. Solar cells using pm-Si:H as their absorbing layer show very interesting degradation kinetics when compared to hydrogenated amorphous silicon (a-Si:H), summarized by macroscopic structural changes and irreversible changes in solar cell characteristics, while nevertheless preserving a higher stabilized efficiency. Notably, pm-Si:H solar cells, once degraded, respond to neither annealing nor further light-soaking. Such results suggest a device degradation mechanism including structural changes, active hydrogen motion, and interface delamination mediated by fast hydrogen diffusion and accumulation at the interface. Interestingly, a similar behavior was reported for a-Si:H solar cells under severe light soaking conditions (at 350 °C or under 50 suns) while pm-Si:H solar cells show such behavior under 1 sun at 40 °C.

Contributions of D0 and non-D0 Gap States to the Kinetics of Light Induced Degradation of Amorphous Silicon under 1 sun Illumination

2001 ◽  
Vol 664 ◽  
Author(s):  
J. Pearce ◽  
X. Niu ◽  
R. Koval ◽  
G. Ganguly ◽  
D. Carlson ◽  
...  
Keyword(s):  
Amorphous Silicon ◽  
Degradation Kinetics ◽  
Hydrogen Dilution ◽  
Spin Resonance ◽  
The Creation ◽  
Staebler Wronski Effect ◽  
Gap States ◽  
Induced Changes ◽  
Induced Defects ◽  
Hydrogenated Amorphous

ABSTRACTLight induced changes to 1 sun degraded steady state (DSS) have been investigated on hydrogenated amorphous silicon (a-Si:H) p-i-n solar cells and corresponding films fabricated with and without hydrogen dilution of silane. Striking similarities are found for the degradation kinetics, between the electron mobility lifetime (μτ) products and the corresponding fill factors (FF). These correlations that exist for both intrinsic materials at temperatures between 25 and 100°C, are present for the DSS as well as in the kinetics, which exihibit distinctly different dependence on temperature. No such correlations are present between μτ, FF and densities of D0 defects, measured with subgap absorption α(E) at 1.2eV, and electron spin resonance (ESR). The creation of non-D0 defects is also clearly indicated by the temperature dependence of the kinetics and the changes in the shape of α(E) with the results suggesting the presence of more than one mechanism for the creation of light induced defects associated with the Staebler-Wronski effect (SWE).

Search for Explaining the Staebler-Wronski Effect

1997 ◽  
Vol 467 ◽  
Author(s):  
H. Fritzsche ◽  
Tucson Az
Keyword(s):  
Spatial Correlation ◽  
Long Range ◽  
Photon Energy ◽  
Structural Changes ◽  
Hydrogen Diffusion ◽  
Critical Value ◽  
Bond Breaking ◽  
Dangling Bond ◽  
High Fields ◽  
Staebler Wronski Effect

ABSTRACTFor twenty years we searched to understand the Staebler-Wronski effect (SWE). New results continue to emerge which invalidate prior interpretations. Recent evidence shows that the SWE is not associated with impurities. Long-range hydrogen diffusion is ruled out because the SWE occurs with comparable efficiency between 400K and the lowest temperatures. Nonradiative geminate recombinations might be important since high fields reduce the SWE significantly. It disappears when the bandgap or the photon energy falls below a critical value. The creation of a metastable density of dangling bond defects has been considered to be its sole manifestation. However, there is mounting evidence for light-induced structural changes which extend throughout the material. The weak bond breaking model emerges as the only viable explanation of the SWE if the expected spatial correlation between defects and hydrogen is destroyed by subsequent recombination events. The SWE is reduced by a favorable microstructure and low hydrogen content. It is suggested that defect pairs have larger recombination coefficients than isolated defects.

Hydrogen Diffusion in Boron-Doped Hydrogenated Amorphous Silicon Films: Crystallization and Induced Structural Changes

2005 ◽  
Vol 864 ◽  
Author(s):  
F. Kail ◽  
A. Hadjadj ◽  
P. Roca i Cabarrocas
Keyword(s):  
Amorphous Silicon ◽  
Structural Changes ◽  
Hydrogen Diffusion ◽  
Hydrogen Plasma ◽  
Hydrogenated Amorphous Silicon ◽  
Silicon Films ◽  
Hydrogen Atoms ◽  
Boron Doped ◽  
Hydrogenated Amorphous ◽  
Positively Charged

AbstractWe have studied the evolution of the structure of boron-doped hydrogenated amorphous silicon films exposed to a hydrogen plasma. From the early stages of exposure, hydrogen diffuses and forms a thick H-rich subsurface. At longer times, hydrogen plasma leads to the formation of a microcrystalline layer via chemical transport without crystallization of the initial layer. We observe that the hydrogen content increases in the films during a plasma exposure and once the microcrystalline layer is formed hydrogen diffuses out of the sample accompanied with a decrease in the boron content. This effect can be attributed to the electric field developed within the heterojunction a-Si:H/μc-Si:H that drives the positively charged hydrogen atoms in the boron-doped layer towards the μc-Si:H layer.

Light-induced changes in hydrogenated amorphous silicon solar cells deposited at the edge of crystallinity

2008 ◽  
Vol 354 (19-25) ◽  
pp. 2155-2159 ◽  
Author(s):  
Wenhui Du ◽  
Xianbo Liao ◽  
Xinmin Cao ◽  
Xiesen Yang ◽  
Xunming Deng ◽  
...  
Keyword(s):  
Solar Cells ◽  
Amorphous Silicon ◽  
Hydrogenated Amorphous Silicon ◽  
Silicon Solar Cells ◽  
Induced Changes ◽  
Hydrogenated Amorphous

Identification of Vacancy-Like Defects in High-Rate Grown a-Si Before and After Light Soaking by Vepas

1998 ◽  
Vol 507 ◽  
Author(s):  
X. Zou ◽  
Y. C. Chan ◽  
D. P. Webb ◽  
Y. W. Lam ◽  
S. H. Lin ◽  
...  
Keyword(s):  
Positron Annihilation ◽  
Structural Changes ◽  
Positron Annihilation Spectroscopy ◽  
High Rate ◽  
Light Illumination ◽  
Vacancy Clusters ◽  
Before And After ◽  
New Type ◽  
Staebler Wronski Effect ◽  
Hydrogenated Amorphous

ABSTRACTWe show how positron annihilation can distinguish vacancies in undoped hydrogenated amorphous silicon by performing Variable Energy Positron Annihilation Spectroscopy experiments before and after light soaking. We find that vacancy clusters, di-vacancies and a new type of single vacancies are created in undoped as-grown a-Si:H thin film by light illumination. The fact that the vacancy clusters are eliminated by the thermal annealing suggests that the Staebler-Wronski effect is closely related to vacancy clusters in a-Si:H material. The creation of vacancy clusters and redistribution of di-vacancies and even single vacancies probably result in photo-induced structural changes in this material.

Hydrogen Diffusion and Thermal Equilibrium of Electronic States in a-Si:H

1987 ◽  
Vol 95 ◽  
Author(s):  
R. A. Street
Keyword(s):  
Thermal Equilibrium ◽  
Hydrogen Diffusion ◽  
Electronic States ◽  
Thermally Induced ◽  
Rate Limiting Step ◽  
Induced Changes ◽  
Rate Limiting ◽  
Hydrogenated Amorphous ◽  
Diffusion Of Hydrogen

AbstractThis paper reviews the recent evidence for thermal equilibrium effects in the electronic behavior of hydrogenated amorphous silicon, and relates the thermally induced changes to the motion of bonded hydrogen. The electronic properties are studied through measurements of d.c conductivity and-.weep out, and the role of hydrogen is explored through its diffusion. The magnitude and doping dependence of the diffusion coefficient DH matches the data on the equilibration of the electronic states. Furthermore both the diffusibn and the relaxation can be described by the same dispersive time dependence. It is argued that the diffusion of hydrogen is the rate limiting step in the the equilibration mechanisms and determines the kinetics.

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