Accelerated light-induced degradation for detecting copper contamination in <i>p</i>-type silicon

Inglese, Alessandro; Lindroos, Jeanette; Savin, Hele

doi:10.1063/1.4927838

Cited by 16 publications

(12 citation statements)

References 32 publications

(32 reference statements)

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“…is surprisingly high, since only very limited Cu‐LID‐related lifetime recovery has been reported . However, as the magnitude of Cu‐LID recovery has been shown to increase with decreasing [Cu] , the recovery in the gettered qm‐Si may be explained by a lower [Cu] than in earlier studies. On the other hand, no recovery was observed in the non‐gettered qm‐Si sample.…”

Section: Resultsmentioning

confidence: 76%

Light‐induced degradation in quasi‐monocrystalline silicon PERC solar cells: Indications on involvement of copper

Vahlman¹,

Wagner²,

Wolny³

et al. 2017

Physica Status Solidi (a)

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High-efficiency solar cell designs such as the passivated emitter and rear cell (PERC) raise the quality requirements for silicon substrates, favoring monocrystalline materials. Seedcast quasi-monocrystalline silicon (qm-Si) is a promising alternative for Czochralski (Cz) Si with potential benefits of lower cost and reduced energy footprint. However, the purity and crystalline quality of qm-Si is not on par with Cz-Si, which can cause efficiency losses for example in the form of light-induced degradation (LID). In this contribution, we study the LID phenomena that can be present in qm-Si PERC solar cells, and compare them to the Cz-Si PERC. Degradation and regeneration are analyzed especially from the viewpoint of Cu impurity, which has until very recently been omitted as a source of LID for this device type. Subsequently, differences in LID behavior between qm-Si and Cz-Si are investigated considering the density of dislocations in the bulk. The results imply that slurry-based wafer slicing may introduce contamination that is capable of causing considerable LID in PERC devices fabricated of Si with inherently high defect density.

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Section: Resultsmentioning

confidence: 76%

Light‐induced degradation in quasi‐monocrystalline silicon PERC solar cells: Indications on involvement of copper

Vahlman¹,

Wagner²,

Wolny³

et al. 2017

Physica Status Solidi (a)

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“…The more pronounced degradation observable in the middle of the Cu-contaminated region is also an indication of higher local Cu concentrations compared to the peripheral areas. 22 In the samples from Group A, the Cu-spot remains clearly distinguishable from the neighboring uncontaminated areas. Hence, this result clearly demonstrates that, in these specimens, the gettering treatment did not result in the suppression of Cu-LID effects.…”

Section: Resultsmentioning

confidence: 97%

Cu gettering by phosphorus-doped emitters in p-type silicon: Effect on light-induced degradation

et al. 2018

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The presence of copper (Cu) contamination is known to cause relevant light-induced degradation (Cu-LID) effects in p-type silicon. Due to its high diffusivity, Cu is generally regarded as a relatively benign impurity, which can be readily relocated during device fabrication from the wafer bulk, i.e. the region affected by Cu-LID, to the surface phosphorus-doped emitter. This contribution examines in detail the impact of gettering by industrially relevant phosphorus layers on the strength of Cu-LID effects. We find that phosphorus gettering does not always prevent the occurrence of Cu-LID. Specifically, air-cooling after an isothermal anneal at 800°C results in only weak impurity segregation to the phosphorus-doped layer, which turns out to be insufficient for effectively mitigating Cu-LID effects. Furthermore, we show that the gettering efficiency can be enhanced through the addition of a slow cooling ramp (-4°C/min) between 800°C and 600°C, resulting in the nearly complete disappearance of Cu-LID effects.

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“…43 In addition to the doping concentration, the degradation kinetics of Cu-LID have been found to significantly dependent on other parameters, such as illumination intensity, temperature, and the presence of bulk defects (e.g., vacancies or dislocations). 7,15 All these parameters are likely to affect the precipitate size distribution and, therefore, result in a different recombination activity of such defects. In addition to providing further evidence of the existence of such precipitates, advanced recombination models that correlate the injectiondependent lifetime with the precipitate radius 44 may also provide additional information on the formation mechanisms.…”

Section: Comparison With Literature Data and Discussionmentioning

confidence: 99%

“…6,7 This phenomenon is referred to as copper-related light-induced degradation (Cu-LID), and it has been suggested to arise from increased bulk recombination [8][9][10] caused by copper precipitation 11,12 or substitutional copper complexes. [13][14][15] Nevertheless, the recombination mechanisms at Cu-LID defects still remain unclear, and the current literature information is lacking in an accurate parametrization of the recombination activity of such defects. Therefore, it is important to determine the recombination parameters of Cu-LID defects in order to quantify their effect on minority carrier lifetime and predict their impact on the overall solar-cell performance.…”

Section: Introductionmentioning

confidence: 99%

Recombination activity of light-activated copper defects in p-type silicon studied by injection- and temperature-dependent lifetime spectroscopy

Inglese

Lindroos

Vahlman

et al. 2016

Journal of Applied Physics

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The presence of copper contamination is known to cause strong light-induced degradation (Cu-LID) in silicon. In this paper, we parametrize the recombination activity of light-activated copper defects in terms of Shockley—Read—Hall recombination statistics through injection- and temperature dependent lifetime spectroscopy (TDLS) performed on deliberately contaminated float zone silicon wafers. We obtain an accurate fit of the experimental data via two non-interacting energy levels, i.e., a deep recombination center featuring an energy level at Ec−Et=0.48−0.62 eV with a moderate donor-like capture asymmetry (k=1.7−2.6) and an additional shallow energy state located at Ec−Et=0.1−0.2 eV, which mostly affects the carrier lifetime only at high-injection conditions. Besides confirming these defect parameters, TDLS measurements also indicate a power-law temperature dependence of the capture cross sections associated with the deep energy state. Eventually, we compare these results with the available literature data, and we find that the formation of copper precipitates is the probable root cause behind Cu-LID.

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Accelerated light-induced degradation for detecting copper contamination in p-type silicon

Abstract: Articles you may be interested in Light-induced degradation and metastable-state recovery with reaction kinetics modeling in boron-doped Czochralski silicon solar cells

Cited by 16 publications

References 32 publications

Light‐induced degradation in quasi‐monocrystalline silicon PERC solar cells: Indications on involvement of copper

Light‐induced degradation in quasi‐monocrystalline silicon PERC solar cells: Indications on involvement of copper

Cu gettering by phosphorus-doped emitters in p-type silicon: Effect on light-induced degradation

Recombination activity of light-activated copper defects in p-type silicon studied by injection- and temperature-dependent lifetime spectroscopy

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