Engineering Solutions and Root-Cause Analysis for Light-Induced Degradation in &lt;italic&gt;p&lt;/italic&gt;-Type Multicrystalline Silicon PERC Modules

Nakayashiki, Kenta; Hofstetter, Jasmin; Morishige, Ashley E.; Li, Tsu-Tsung Andrew; Needleman, David Berney; Jensen, Mallory A.; Buonassisi, Tonio

doi:10.1109/jphotov.2016.2556981

Cited by 134 publications

(98 citation statements)

References 58 publications

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“…Nevertheless, the largest degradation is observed in the non‐textured edges of the SiN x ‐passivated b‐Si cells, which is an interesting finding and will be discussed later in more detail. Finally, Figure C reveals that the degradation is rather uniform laterally in good grain areas, which is characteristic of LeTID . However, defect clusters show slightly stronger LeTID, as reported recently, which is even more pronounced in the acidic‐textured cells (Figure E,F).…”

Section: Resultssupporting

confidence: 80%

“…The reduction in IQE is the strongest in the ~850 to 1100‐nm wavelength range, which indicates that the degradation occurs in the bulk or at the rear surface. Consistently, earlier studies have suggested that LeTID is mainly a bulk effect . Interestingly, both surface passivation schemes produce nearly identical IQE spectra also in the short wavelength range (both before and after degradation), although it is generally understood that AlO x is unfavorable for phosphorus emitter passivation due to the high density of negative fixed charges in the thin film .…”

Section: Resultssupporting

confidence: 77%

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Impact of black silicon on light‐ and elevated temperature‐induced degradation in industrial passivated emitter and rear cells

Pasanen

Modanese

Vähänissi

et al. 2018

Progress in Photovoltaics

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Light and elevated‐temperature induced degradation (LeTID) is currently a severe issue in passivated emitter and rear cells (PERC). In this work, we study the impact of surface texture, especially a black silicon (b‐Si) nanostructure, on LeTID in industrial p‐type mc‐Si PERC. Our results show that during standard LeTID conditions the b‐Si cells with atomic‐layer‐deposited aluminum oxide (AlOx) front surface passivation show no degradation despite the presence of a hydrogen‐rich AlOx/SiNx passivation stack on the rear. Furthermore, b‐Si solar cells passivated with silicon nitride (SiNx) on the front lose only 1.5%rel of their initial power conversion efficiency, while the acidic‐textured equivalents degrade by nearly 4%rel under the same conditions. Correspondingly, clear degradation is visible in the internal quantum efficiency (IQE) of the acidic‐textured cells, especially in the ~850 to 1100‐nm wavelength range confirming that the degradation occurs in the bulk, while the IQE remains nearly unaffected in the b‐Si cells. The observations are supported by spatially resolved photoluminescence (PL) maps, which show a clear contrast in the degradation behavior of b‐Si and acidic‐textured cells, especially in the case of SiNx front surface passivation. The PL maps also suggest that the magnitude of LeTID scales with surface area of the texture, rather than wafer thickness that was recently reported, although the b‐Si cells are slightly thinner (140 vs 165 μm). The results indicate that b‐Si has a positive impact on LeTID, and hence, benefits provided by b‐Si are not limited only to the excellent optical properties, as commonly understood.

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Section: Resultssupporting

confidence: 80%

Section: Resultssupporting

confidence: 77%

Impact of black silicon on light‐ and elevated temperature‐induced degradation in industrial passivated emitter and rear cells

Pasanen

Modanese

Vähänissi

et al. 2018

Progress in Photovoltaics

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“…Furthermore, several other studies [29][30][31][32] have consistently reported that the magnitude of LeTID increases with peak firing temperature, with peak temperatures 650 C leading to little or no LeTID, while temperatures between 700 C and 950 C trigger degradation. These trends in degradation behaviour with firing temperature and cooling rate correlate well with the present study.…”

Section: à3mentioning

confidence: 84%

Rapid thermal anneal activates light induced degradation due to copper redistribution

Nampalli

Laine

Colwell

et al. 2018

Applied Physics Letters

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While it is well known that copper impurities can be relatively easily gettered from the silicon bulk to the phosphorus or boron–doped surface layers, it has remained unclear how thermally stable the gettering actually is. In this work, we show experimentally that a typical rapid thermal anneal (RTA, a few seconds at 800 °C) used commonly in the semiconductor and photovoltaic industries is sufficient to release a significant amount of Cu species from the phosphorus-doped layer to the wafer bulk. This is enough to activate the so-called copper-related light-induced degradation (Cu-LID) which results in significant minority carrier lifetime degradation. We also show that the occurrence of Cu-LID in the wafer bulk can be eliminated both by reducing the RTA peak temperature from 800 °C to 550 °C and by slowing the following cooling rate from 40–60 °C/s to 4 °C/min. The behavior is similar to what is reported for Light and Elevated Temperature degradation, indicating that the role of Cu cannot be ignored when studying other LID phenomena. Numeric simulations describing the phosphorus diffusion and the gettering process reproduce the experimental trends and elucidate the underlying physical mechanisms.

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“…It is known that high temperature steps during cell processing are influencing the strength of this degradation, and that they can be minimized by an effective external gettering [26]. It could also be shown that the firing step has a strong influence on LeTID strength, and that it can be minimized by applying a co-firing step at lower temperature [27], [28]. Recently, it could be demonstrated that an additional second firing step at lower peak temperature can significantly reduce the LeTID strength, and it was pointed out that although LeTID can be reduced, cell efficiency (series resistance) might be affected by this second lower temperature firing step [29].…”

Section: E Consequences For Mc-si Degradation Phenomenamentioning

confidence: 99%

Impact of Extended Contact Cofiring on Multicrystalline Silicon Solar Cell Parameters

Peral

Dastgheib-Shirazi

Fano

et al. 2017

IEEE J. Photovoltaics

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Engineering Solutions and Root-Cause Analysis for Light-Induced Degradation in <italic>p</italic>-Type Multicrystalline Silicon PERC Modules

Cited by 134 publications

References 58 publications

Impact of black silicon on light‐ and elevated temperature‐induced degradation in industrial passivated emitter and rear cells

Impact of black silicon on light‐ and elevated temperature‐induced degradation in industrial passivated emitter and rear cells

Rapid thermal anneal activates light induced degradation due to copper redistribution

Impact of Extended Contact Cofiring on Multicrystalline Silicon Solar Cell Parameters

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