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.

Evidence for Long-range Hydrogen Motion in a-Si:H under Room-temperature Illumination Using Raman Scattering of Amorphous Tungsten Oxide Overlayer

2001 ◽  
Vol 664 ◽  
Author(s):  
Hyeonsik M. Cheong ◽  
Se-Hee Lee ◽  
Brent Nelson ◽  
Angelo Mascarenhas ◽  
Sayten K. Deb
Keyword(s):  
Raman Spectrum ◽  
Tungsten Oxide ◽  
Long Range ◽  
Room Temperature ◽  
Hydrogen Diffusion ◽  
High Sensitivity ◽  
Raman Signal ◽  
Hydrogen Atoms ◽  
Long Distance ◽  
Staebler Wronski Effect

ABSTRACTWe demonstrate that one can detect minuscule amounts of hydrogen diffusion out of a-Si:H under illumination at room temperature, by monitoring the changes in the Raman spectrum of amorphous tungsten oxide as a function of illumination. The Staebler-Wronski effect, the light-induce creation of metastable defects in hydrogenated amorphous silicon (a-Si:H), has been one of the major problems that has limited the performance of such devices as solar cells. Recently, Branz suggested the hydrogen collision model that can explain many aspects of the Staebler-Wronski effect. One of the main predictions of this model is that the photogenerated mobile hydrogen atoms can move a long distance at room temperature. However, light-induced hydrogen motion in a-Si:H has not been experimentally observed at room temperature. We utilized the high sensitivity of the Raman spectrum of electrochromic a-WO3 to hydrogen insertion to probe the long-range motion of hydrogen at room temperature. We deposited a thin (200 nm) layer of a-WO3 on top of a-Si:H, and under illumination, a change in the Raman spectrum was detected. By comparing the Raman signal changes with those for control experiments where hydrogen is electrochemically inserted into a-WO3, we can estimate semiquantitatively the amount of hydrogen that diffuses out of the a-Si:H layer.

Assessment of Weak Si-Si Bond Breaking Mechanisms of the Staebler-Wronski Effect

1991 ◽  
Vol 219 ◽  
Author(s):  
R. Biswas ◽  
I. Kwon ◽  
C. M. Soukoulis
Keyword(s):  
Interatomic Potential ◽  
Bond Breaking ◽  
Dangling Bond ◽  
Hydrogenated Silicon ◽  
Amorphous Hydrogenated Silicon ◽  
Excited Carrier ◽  
Carrier Energy ◽  
The Stability ◽  
Staebler Wronski Effect ◽  
New Si

ABSTRACTThe mechanisms of the Staebler-Wronski effect are investigated by examining the stability of computer-generated amorphous hydrogenated silicon networks with a molecular dynamics approach. Models with both monohydride and dihydride species are examined. A new Si-H interatomic potential is utilized for the simulations. A localized excitation is used to model the non-radiative transfer of photo-excited carrier energy to the lattice. The a-Si:H model with only monohydride species is stable to bond-breaking excitations. The a-Si:H model with both monohydride and dihydride species is less stable and exhibits, after local excitations, higher energy dangling bond states that can however be easily annealed away.

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.

scholarly journals Structural Changes in the Acceptor Site of Photosystem II upon Ca2+/Sr2+ Exchange in the Mn4CaO5 Cluster Site and the Possible Long-Range Interactions

Biomolecules ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 371
Author(s):  
Koua
Keyword(s):  
Crystal Structure ◽  
Photosystem Ii ◽  
Long Range ◽  
Electron Acceptor ◽  
Structural Changes ◽  
Acceptor Site ◽  
Oxygen Evolving Complex ◽  
Long Range Interactions ◽  
Structural Perturbations ◽  
Oxygen Evolving

The Mn4CaO5 cluster site in the oxygen-evolving complex (OEC) of photosystem II (PSII) undergoes structural perturbations, such as those induced by Ca2+/Sr2+ exchanges or Ca/Mn removal. These changes have been known to induce long-range positive shifts (between +30 and +150 mV) in the redox potential of the primary quinone electron acceptor plastoquinone A (QA), which is located 40 Å from the OEC. To further investigate these effects, we reanalyzed the crystal structure of Sr-PSII resolved at 2.1 Å and compared it with the native Ca-PSII resolved at 1.9 Å. Here, we focus on the acceptor site and report the possible long-range interactions between the donor, Mn4Ca(Sr)O5 cluster, and acceptor sites.

Structural changes from polyimide films to graphite: Part IV. Novax and PPT

1995 ◽  
Vol 10 (4) ◽  
pp. 1024-1027 ◽  
Author(s):  
C. Bourgerette ◽  
A. Oberlin ◽  
M. Inagaki
Keyword(s):  
Long Range ◽  
Structural Changes ◽  
Film Plane ◽  
High Rank ◽  
Polyimide Films ◽  
Electron Microscopies ◽  
Higher Temperature ◽  
Cross Linker ◽  
Graphite Part

Various polyimide films (Kapton, Upilex, Novax, and PPT) were carbonized and graphitized up to 3000 °C. They were studied by optical and electron microscopies. All films retaining oxygen as a cross linker over 1000 °C, i.e., Kapton, Upilex, and Novax, graphitize as anthracites (high rank coals) do. They get a long range statistical orientation parallel to the film plane with a nanotexture of flattened pores. Graphitization is both sudden and perfect above 2100 °C when the pore walls break. Since oxygen is released at 1000 °C, the film PPT behaves as a compact nonporous graphitizing carbon (orientation parallel to the film plane). Thermal graphitization is progressive and begins at a higher temperature.

scholarly journals Correlation between long range and local structural changes in Ni-rich layered materials during charge and discharge process

2019 ◽  
Vol 412 ◽  
pp. 336-343 ◽  
Author(s):  
Shiyao Zheng ◽  
Chaoyu Hong ◽  
Xiaoyun Guan ◽  
Yuxuan Xiang ◽  
Xiangsi Liu ◽  
...  
Keyword(s):  
Long Range ◽  
Structural Changes ◽  
Layered Materials ◽  
Discharge Process

scholarly journals Non-Markovian Quantum Optics with Three-Dimensional State-Dependent Optical Lattices

Quantum ◽  
2018 ◽  
Vol 2 ◽  
pp. 97 ◽  
Author(s):  
A. González-Tudela ◽  
J. I. Cirac
Keyword(s):  
Quantum Optics ◽  
Spectral Density ◽  
Long Range ◽  
Photon Energy ◽  
Optical Lattices ◽  
Cold Atoms ◽  
Three Dimensional ◽  
Collective Effects ◽  
State Dependent ◽  
Anisotropic Interactions

Quantum emitters coupled to structured photonic reservoirs experience unconventional individual and collective dynamics emerging from the interplay between dimensionality and non-trivial photon energy dispersions. In this work, we systematically study several paradigmatic three dimensional structured baths with qualitative differences in their bath spectral density. We discover non-Markovian individual and collective effects absent in simplified descriptions, such as perfect subradiant states or long-range anisotropic interactions. Furthermore, we show how to implement these models using only cold atoms in state-dependent optical lattices and show how this unconventional dynamics can be observed with these systems.

scholarly journals Long-Range Structural Changes in the Meiotic Nucleus Revealed by Changes in Stress Communication Along the Chromosome

2018 ◽  
Vol 114 (3) ◽  
pp. 30a
Author(s):  
Trent Newman ◽  
Bruno G. Beltran ◽  
James McGehee ◽  
Cori Cahoon ◽  
Daniel Elnatan ◽  
...  
Keyword(s):  
Long Range ◽  
Structural Changes

scholarly journals Mediator facilitates transcriptional activation and dynamic long-range contacts at the IgH locus during class switch recombination

2016 ◽  
Vol 213 (3) ◽  
pp. 303-312 ◽  
Author(s):  
Anne-Sophie Thomas-Claudepierre ◽  
Isabelle Robert ◽  
Pedro P. Rocha ◽  
Ramya Raviram ◽  
Ebe Schiavo ◽  
...  
Keyword(s):  
B Cells ◽  
Long Range ◽  
Transcriptional Activation ◽  
Transcription Initiation ◽  
Structural Changes ◽  
Class Switch Recombination ◽  
Mediator Complex ◽  
Loop Formation ◽  
Class Switch ◽  
Igh Locus

Immunoglobulin (Ig) class switch recombination (CSR) is initiated by the transcription-coupled recruitment of activation-induced cytidine deaminase (AID) to Ig switch regions (S regions). During CSR, the IgH locus undergoes dynamic three-dimensional structural changes in which promoters, enhancers, and S regions are brought to close proximity. Nevertheless, little is known about the underlying mechanisms. In this study, we show that Med1 and Med12, two subunits of the mediator complex implicated in transcription initiation and long-range enhancer/promoter loop formation, are dynamically recruited to the IgH locus enhancers and the acceptor regions during CSR and that their knockdown in CH12 cells results in impaired CSR. Furthermore, we show that conditional inactivation of Med1 in B cells results in defective CSR and reduced acceptor S region transcription. Finally, we show that in B cells undergoing CSR, the dynamic long-range contacts between the IgH enhancers and the acceptor regions correlate with Med1 and Med12 binding and that they happen at a reduced frequency in Med1-deficient B cells. Our results implicate the mediator complex in the mechanism of CSR and are consistent with a model in which mediator facilitates the long-range contacts between S regions and the IgH locus enhancers during CSR and their transcriptional activation.

Role of LHCII-containing macrodomains in the structure, function and dynamics of grana

2000 ◽  
Vol 27 (3) ◽  
pp. 279 ◽  
Author(s):  
G. Garab ◽  
L. Mustárdy
Keyword(s):  
Excitation Energy ◽  
Long Range ◽  
Structural Changes ◽  
Higher Plants ◽  
Three Dimensional ◽  
Dimensional Structure ◽  
Lateral Heterogeneity ◽  
Long Distance ◽  
3D Network

In higher plants and green algae two types of thylakoids are distinguished, granum (stacked) and stroma (unstacked) thylakoids. They form a three-dimensional (3D) network with large lateral heterogeneity: photosystem II (PSII) and the associated main chlorophyll a/b light-harvesting complex (LHCII) are found predominantly in the stacked region, while PSI and LHCI are located mainly in the unstacked region of the membrane. This picture emerged from the discovery of the physical separation of the two photosystems (Boardman and Anderson 1964). Granal chloroplasts possess significant flexibility, which is essential for optimizing the photosynthetic machinery under various environmental conditions. However, our understanding concerning the assembly, structural dynamics and regulatory functions of grana is far from being complete. In this paper we overview the significance of the three-dimensional structure of grana in the absorption properties, ionic equilibrations, and in the diffusion of membrane components between the stacked and unstacked regions. Further, we discuss the role of chiral macrodomains in the grana. Lateral heterogeneity of thylakoid membranes is proposed to be a consequence of the formation of macrodomains constituted of LHCII and PSII; their long range order permits long distance migration of excitation energy, which explains the energetic connectivity of PSII particles. The ability of macrodomains to undergo light-induced reversible structural changes lends structural flexibility to the granum. In purified LHCII, which has also been shown to form stacked lamellar aggregates with long range chiral order, excitation energy migrates for large distances; these macroaggregates are also capable of undergoing light-induced reversible structural changes and fluorescence quenching. Hence, some basic properties of grana appear to originate from its main constituent, the LHCII.

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