External and Internal Gettering of Interstitial Iron in Silicon for Solar Cells

Macdonald, Daniel; Liu, AnYao; Phang, Sieu Pheng

doi:10.4028/www.scientific.net/ssp.205-206.26

Cited by 13 publications

(16 citation statements)

References 30 publications

(53 reference statements)

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“…Therefore, a large fraction of Fe is in precipitated form. Some dissolution of this precipitated Fe is expected during such high temperature processes, 24 however, our previous study 18,25 on neighbouring wafers found that the amount of dissolution is not significant compared to the initial as-cut interstitial Fe concentrations on the order of 10 12 -10 13 cm À3 . It was found that the neighbouring wafers in the as-cut state, either oxidised and removed from the furnace at 1000 C, or oxidised at 1000 C followed by a 10 C/min cool-down to 700 C before being removed from the furnace, all show similar average interstitial Fe concentrations.…”

Section: Methodsmentioning

confidence: 86%

Precipitation of iron in multicrystalline silicon during annealing

Liu

Macdonald

2014

Journal of Applied Physics

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In this paper, the precipitation kinetics of iron in multicrystalline silicon during moderate temperature annealing are systematically studied with respect to annealing time, temperature, iron super-saturation level, and different types and densities of precipitation sites. The quantitative analysis is based on examining the changes in the concentrations and distributions of interstitial iron in multicrystalline silicon wafers after annealing at 400–700 °C. This is achieved by using the photoluminescence imaging technique to produce high-resolution spatially resolved images of the interstitial iron concentrations. The concentrations of interstitial iron are found to decrease exponentially with the annealing time. Comparison of the precipitation time constants of wafers annealed at different temperatures and of different initial interstitial iron concentrations indicates that higher levels of iron super-saturation result in faster precipitation processes. The impact of iron super-saturation on the precipitation kinetics becomes increasingly important at low levels of super-saturation, while its impact saturates at very high levels of super-saturation (above 1000). Some grain boundaries are shown to act as effective precipitation sites for iron during annealing, and the reduction in the interstitial iron concentrations in the intra-grain regions is found to be mainly due to precipitation at dislocations. Some important differences between the iron precipitation behaviour at the grain boundaries and at the intra-grain dislocations are discussed. The effect of hydrogenation of the multicrystalline silicon wafers on the apparent iron precipitation rate is also presented and discussed.

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Section: Methodsmentioning

confidence: 86%

Precipitation of iron in multicrystalline silicon during annealing

Liu

Macdonald

2014

Journal of Applied Physics

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“…However, our samples are mc-Si. Thus, besides this external gettering, the second sample may also experience internal gettering, in which at least some metal impurities are preferentially decorated around the GBs and sub-GBs instead of being captured in the phosphorus diffused layers [27]. Therefore, although the global concentration of metal impurities such as Fe will be reduced by the external gettering, the local concentration at GBs and sub-GBs could, in principle, actually be higher than that of the as-cut sample.…”

Section: Results and Analysismentioning

confidence: 99%

Micrometer-Scale Deep-Level Spectral Photoluminescence From Dislocations in Multicrystalline Silicon

Nguyen

Rougieux

Wang

et al. 2015

IEEE J. Photovoltaics

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Abstract-Micrometer-scale deep-level spectral photoluminescence (PL) from dislocations is investigated around the subgrain boundaries in multicrystalline silicon. The spatial distribution of the D lines is found to be asymmetrically distributed across the subgrain boundaries, indicating that defects and impurities are decorated almost entirely on one side of the subgrain boundaries. In addition, the D1 and D2 lines are demonstrated to have different origins due to their significantly varying behaviors after processing steps. D1 is found to be enhanced when the dislocations are cleaned of metal impurities, whereas D2 remains unchanged. Finally, the D4 and D3 lines are proposed to have different origins since their energy levels are shifted differently as a function of distance from the subgrain boundaries.

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“…“Red zone” (≈5 cm) in cast mono‐like silicon ingot can be twice as wide as that found in conventional cast mc silicon, which significantly reduce the yield of cast mono‐like silicon ingot. Red zone can reduce the carrier lifetime of p‐type cast mono‐like silicon wafers by more than two orders of magnitude and the material yield (the number of wafers qualified for producing solar cells/the total number of wafers from the red zone of the ingot) by one order of magnitude 57 . As reported, “red zone” is mainly attributed to the iron contamination; however, there are various hypotheses for the detailed mechanisms.…”

Section: Defects In Cast Mono‐like Silicon and Methods To Suppress Themmentioning

confidence: 97%

Defect engineering in cast mono‐like silicon: A review

Song

2020

Progress in Photovoltaics

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Cast mono‐like silicon is a promising material for next‐generation silicon solar cells with higher efficiency and lower cost compared with currently commercialized silicon solar cells. So far, cast mono‐like silicon technique still faces several problems, including multicrystallization, dislocation clusters, sub‐grain boundaries, and impurity contamination, which hinder its mass‐scale applications in photovoltaic industry. In this review, we will introduce these common problems in turn and discuss a multitude of the reported studies on eliminating these problems. Furthermore, light and elevated temperature‐induced degradation (LeTID) was recently reported to be a severe problem of cast mono‐like silicon solar cells, which can cause power loss over 10% relative. This review will introduce the behaviors and the proposed mechanisms of LeTID as well as the methods to suppress LeTID in Section 4. In the subsequent section, the efficiency potential and distribution of cast mono‐like silicon solar cells are discussed. At last, a comprehensive summary will be given for this review.

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External and Internal Gettering of Interstitial Iron in Silicon for Solar Cells

Cited by 13 publications

References 30 publications

Precipitation of iron in multicrystalline silicon during annealing

Precipitation of iron in multicrystalline silicon during annealing

Micrometer-Scale Deep-Level Spectral Photoluminescence From Dislocations in Multicrystalline Silicon

Defect engineering in cast mono‐like silicon: A review

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