Dislocation density reduction in multicrystalline silicon solar cell material by high temperature annealing

Hartman, Katy; Bertoni, Mariana I.; Serdy, James; Buonassisi, Tonio

doi:10.1063/1.2990644

Cited by 73 publications

(47 citation statements)

References 14 publications

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“…When the annealing temperature was about 1360°C, few etch-pits apart from the grain boundaries could be observed clearly. The results show that when the annealing temperature varies from 1100 to 1400°C,the dislocation density in the bulk UMG multi-Si decreases as the annealing temperature increases, which is consistent with the experimental results of Hartman et al [7]. It has been reported that metal precipitates at grain boundaries and dislocations can gradually dissolve and diffuse into the neighboring regions above 1000°C [9].…”

Section: Influence On Dislocation Densitysupporting

confidence: 81%

“…This finding is in conflict with the results of Hartman et al who reported that dislocation density had a decisive influence on the minority carrier lifetime of Si materials, especially multi-Si materials [7]. As well as the dislocation and grain boundary densities, the structure, chemical state and spatial distribu-tion of the metal impurities in the wafers have a significant or even decisive influence on the electrical properties of the UMG-Si materials, especially multi-Si materials with a high concentration of impurities.…”

Section: Influence On Electrical Propertiescontrasting

confidence: 56%

“…A divergent issue is whether or not the dislocation density is the main factor that determines the carrier recombination activity among the structural defects and precipitates. Hartman et al have ever reported that even relatively "clean" dislocations with weak individual recombination activity can have a large cumulative impact on minority carrier lifetime when present in the high concentrations typical of underperforming regions of multi-Si [7]. They believed that higher annealing temperatures (>1170°C) would allow dislocation annihilation within minutes, suppressing minority carrier recombination activity.…”

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confidence: 99%

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Effects of high temperature annealing on the dislocation density and electrical properties of upgraded metallurgical grade multicrystalline silicon

Hong

Shen

2011

Chin. Sci. Bull.

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High temperature annealing was performed on upgraded metallurgical grade multicrystalline silicon (UMG multi-Si) wafers with a purity of 99.999%. The samples were mechanically polished and chemically etched, and then the microstructures were observed by a scanning electron microscope (SEM). The minority carrier lifetime and resistivity of the samples were measured using microwave photoconductance decay and four-point probe techniques, respectively. The results show that the electrical properties of the samples decrease rather than increase as the annealing temperature increases, while the number of dislocations in bulk Si reduced or even disappeared after annealing for 6 hours at 1100-1400°C. It is considered that the structural microdefects induced by the high concentration of metal impurities (including interstitial or substitutional impurities and nanoscale precipitates) determine the minority carrier recombination activity and thus the electrical properties of UMG multi-Si wafers rather than dislocations in bulk Si.upgraded metallurgical grade multicrystalline silicon, high temperature annealing, dislocation density, minority carrier lifetime Citation:Xu H B, Hong R J, Shen H. Effects of high temperature annealing on the dislocation density and electrical properties of upgraded metallurgical grade multicrystalline silicon.

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Section: Influence On Dislocation Densitysupporting

confidence: 81%

Section: Influence On Electrical Propertiescontrasting

confidence: 56%

mentioning

confidence: 99%

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Effects of high temperature annealing on the dislocation density and electrical properties of upgraded metallurgical grade multicrystalline silicon

Hong

Shen

2011

Chin. Sci. Bull.

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“…Their behaviour is of fundamental importance for the performance of thermoelectric devices 2 , nano-electronics 3,4 and solar cells 5,6 . In structural engineering alloys, used for high-performance aerospace applications, dislocation-mediated slip is one of the main deformation mechanisms 7 .…”

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confidence: 99%

X-ray micro-beam characterization of lattice rotations and distortions due to an individual dislocation

et al. 2013

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Understanding and controlling the behaviour of dislocations is crucial for a wide range of applications, from nano-electronics and solar cells to structural engineering alloys. Quantitative X-ray diffraction measurements of the strain fields due to individual dislocations, particularly in the bulk, however, have thus far remained elusive. Here we report the first characterization of a single dislocation in a freestanding GaAs/In 0.2 Ga 0.8 As/GaAs membrane by synchrotron X-ray micro-beam Laue diffraction. Our experimental X-ray data agrees closely with textbook anisotropic elasticity solutions for dislocations, providing one of few experimental validations of this fundamental theory. On the basis of the experimental uncertainty in our measurements, we predict the X-ray beam size required for threedimensional measurements of lattice strains and rotations due to individual dislocations in the material bulk. These findings have important implications for the in situ study of dislocation structure formation, self-organization and evolution in the bulk.

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“…During heating, we assume a negligible precipitate dissolution energy barrier in all models-precipitates can start to dissolve the instant the solid solubility exceeds [Fe,] [26,48]. Lastly, we assume that structural defects are stationary and neither generated nor annihilated by processing, as the used temperature ranges are not high enough to allow significant dislocation movement [49][50][51].…”

Section: Systematic Variation Of Model Elementsmentioning

confidence: 99%

Building intuition of iron evolution during solar cell processing through analysis of different process models

et al. 2015

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An important aspect of Process Simulators for photovoltaics is prediction of defect evolution during device fabrication. Over the last twenty years, these tools have accelerated process optimization, and several Process Simulators for iron, a ubiquitous and deleterious impurity in silicon, have been developed. The diversity of these tools can make it difficult to build intuition about the physics governing iron behavior during processing. Thus, in one unified software environment and using self-consistent terminology, we combine and describe three of these Simulators. We vary structural defect distribution and iron precipitation equations to create eight distinct Models, which we then use to simulate different stages of processing. We find that the structural defect distribution influences the final interstitial iron concentration ([Fe,]) more strongly than the iron precipitation equations. We identify two regimes of iron behavior: (1) diffusivity-limited, in which iron evolution is kinetic ally limited and bulk [Fe,] predictions can vary by an order of magnitude or more, and (2) solubility-limited, in which iron evolution is near thermodynamic equilibrium and the Models yield similar results. This rigorous analysis provides new intuition that can inform Process Simulation, material, and process development, and it enables scientists and engineers to choose an appropriate level of Model complexity based on wafer type and quality, processing conditions, and available computation time.

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Dislocation density reduction in multicrystalline silicon solar cell material by high temperature annealing

Cited by 73 publications

References 14 publications

Effects of high temperature annealing on the dislocation density and electrical properties of upgraded metallurgical grade multicrystalline silicon

Effects of high temperature annealing on the dislocation density and electrical properties of upgraded metallurgical grade multicrystalline silicon

X-ray micro-beam characterization of lattice rotations and distortions due to an individual dislocation

Building intuition of iron evolution during solar cell processing through analysis of different process models

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