Degradation and Recovery of <i>n</i>-Type Multi-Crystalline Silicon Under Illuminated and Dark Annealing Conditions at Moderate Temperatures

Vargas, Carlos Arturo Parra; Nie, Shouping; Chen, Daniel; Hallam, Brett; Coletti, Gianluca; Hameiri, Ziv

doi:10.1109/jphotov.2018.2885711

Cited by 18 publications

(13 citation statements)

References 48 publications

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“…Whereas the 3n sample does not show any degradation in accordance with [5] and [9], a decrease of ∆N leq is visible for the 200n sample. Recent results have shown that LeTID in n-type mc-Si can occur [23], [24], whereas these results indicate that LeTID also might influence 200 Ω•cm n-type FZ-Si.…”

Section: B Influence Of Base Materialsmentioning

confidence: 86%

Influencing Light and Elevated Temperature Induced Degradation and Surface-Related Degradation Kinetics in Float-Zone Silicon by Varying the Initial Sample State

Hammann

Engelhardt

Sperber

et al. 2020

IEEE J. Photovoltaics

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Light and elevated temperature induced degradation (LeTID) kinetics in float-zone silicon are investigated by varying the initial sample state, composed of different base material, base doping, SiN x :H films, and subsequent firing, and/or annealing steps. The approach of deliberately changing the initial sample state is shown to allow for specific studies of influences of LeTID kinetics. Bulk-and surface-related degradations are examined separately and the influence on the kinetics of bulk-and surface-related degradation is illustrated by a four-state and three-state model, respectively. In case of bulk-related degradation, an increase in defect density because of the firing step is shown, whereas the annealing step has an inverse effect. Both temperature stepsindividually and combined-influence the transition rates of bulkrelated degradation and regeneration by presumably changing the distribution of a defect precursor. For surface-related degradation, the firing step reduces the transition rate from the initial to the degraded state. In addition, the influence of a comparably humid atmosphere and the absence of UV light are found to be negligible. Index Terms-Bulk-related degradation (BRD), crystalline silicon, defect density, float zone (FZ), light and elevated temperature induced degradation (LeTID), surface-related degradation (SRD). I. INTRODUCTION L IGHT and elevated temperature induced degradation (LeTID) is a degradation phenomenon first found especially in mc-Si in 2012 [1]. Recently, a similar or the same phenomenon was discovered in Cz-Si [2], [3] and float-zone (FZ) Si [4], [5]. Compared with other degradation effects like boron-oxygen-related (BO) degradation [6], higher treatment temperatures >50°C are needed to investigate the effect on experimentally viable time scales [1], [7]. Besides LeTID, which is a bulk-related degradation (BRD), a second degradation phenomenon is visible and can be identified as a This work was supported by the German Federal Ministry for Economic Affairs and Energy under Contracts 0324226A and 0324001.

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Section: B Influence Of Base Materialsmentioning

confidence: 86%

Influencing Light and Elevated Temperature Induced Degradation and Surface-Related Degradation Kinetics in Float-Zone Silicon by Varying the Initial Sample State

Hammann

Engelhardt

Sperber

et al. 2020

IEEE J. Photovoltaics

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“…[223][224][225][226][227] Although the latter primarily affects PERC solar cells fabricated on multicrystalline silicon cells, other materials such as p-type Cz, n-type Cz, and n-type multi are also susceptible. [228][229][230][231][232] It should be noted, that although we highlight the benefits of hydrogen for silicon solar cells in this paper, hydrogen can also be detrimental for silicon solar cells. Hydrogen is known to form platelets 93,233 and a range of complexes with impurities such as carbon, 234 oxygen, 235 and metals 236,237 and structural defects such as vacancyhydrogen complexes.…”

Section: Advanced Hydrogenation Of Silicon Solar Cellsmentioning

confidence: 99%

“…[242][243][244][245][246][247] In particular, many of the behaviours of LeTID are consistent with the behaviour of hydrogen, such as the increased introduction of hydrogen with increasing firing temperature, 227 the ability to generate H 0 in the dark at low temperatures and induce the degradation without excess minority carriers, and the ability to cause the degradation in practically any commercially available silicon material for solar cells. 228,229,231,232,244,248,249 Attempts to eliminate the degradation in the bulk can result in the migration of hydrogen to the surfaces, leading to increased contact resistance. 82,94,95 There are a number of mechanisms that could lead to increased contact resistance such as counter doping of the heavily doped region, or the passivation of dopants or defects at the metal/silicon interface, in what is now becoming known as "hydrogen-induced degradation".…”

Section: Advanced Hydrogenation Of Silicon Solar Cellsmentioning

confidence: 99%

Development of advanced hydrogenation processes for silicon solar cells via an improved understanding of the behaviour of hydrogen in silicon

Hallam

Hamer

Wenham

et al. 2020

Progress in Photovoltaics

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The understanding and development of advanced hydrogenation processes for silicon solar cells are presented. Hydrogen passivation is incorporated into virtually all silicon solar cells, yet the properties of hydrogen in silicon are still poorly understood. This is largely due to the complex behaviour of hydrogen in silicon and its ability to exist in many different forms in the lattice. For commercial solar cells, hydrogen is introduced into the device through the deposition of hydrogen-containing dielectric layers and the subsequent metallisation firing process. This process can readily passivate structural defects such as grain boundaries but is ineffective at passivating numerous defects in silicon solar cells such as the boron-oxygen complex, responsible for light-induced degradation in p-type Czochralski silicon. This difficulty is due to the need to first form the boron-oxygen defect and also due to atomic hydrogen naturally occupying low-mobility and low-reactivity charge states. However, these challenges can be overcome using advanced hydrogenation processes incorporating excess carrier generation from illumination or current injection that increase the concentration of the highly mobile and reactive neutral charge state. As a result, after fast firing, additional low-temperature advanced hydrogenation processes incorporating illumination can be implemented to enable the passivation of difficult defects like the boron-oxygen complex. With the implementation of such processes for industrial silicon solar cells, efficiency improvements of 1.1% absolute can be obtained.

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“…This effect is often seen on samples that undergo firing at high temperature followed by a degradation and recovery cycle, where the final lifetime is significantly higher than the lifetime measured after firing, with at least some portion of this increase being due to the sample already starting with a degraded lifetime after firing. [43][44][45][46]…”

Section: A Dependence On Firingmentioning

confidence: 99%

Progress in the understanding of light‐ and elevated temperature‐induced degradation in silicon solar cells: A review

Chen

Contreras

Ciesla

et al. 2020

Progress in Photovoltaics

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At present, the commercially dominant and rapidly expanding PV-device technology is based on the passivated emitter and rear cell (PERC) design developed at UNSW. However, this technology has been found to suffer from a carrier-induced degradation commonly referred to as 'lightand elevated temperature-induced degradation' (LeTID) and can result in up to 16% relative performance losses. LeTID was recently shown to occur in almost every type of silicon wafer, independent of the doping material. Even though the degradation mechanism is known to recover under normal operation conditions, it is a lengthy process that drastically affects the energy yield, stability and, ultimately, the levelized cost of electricity (LCOE) of installed systems.Despite the joint effort of many research groups, the root cause of the degradation is still unknown. Here, we provide an overview of the existing literature and describe key LeTID characteristics and how these have led to the development of various theories of the underlying mechanism. Further, given the continuously appearing and strong evidence of hydrogen involvement in LeTID, many mitigation methods concerning hydrogenation have been suggested. We discuss such reported methods, bearing in mind crucial consumer necessities in terms of sustained cell performance and minimised LCOE.

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Degradation and Recovery of n-Type Multi-Crystalline Silicon Under Illuminated and Dark Annealing Conditions at Moderate Temperatures

Cited by 18 publications

References 48 publications

Influencing Light and Elevated Temperature Induced Degradation and Surface-Related Degradation Kinetics in Float-Zone Silicon by Varying the Initial Sample State

Influencing Light and Elevated Temperature Induced Degradation and Surface-Related Degradation Kinetics in Float-Zone Silicon by Varying the Initial Sample State

Development of advanced hydrogenation processes for silicon solar cells via an improved understanding of the behaviour of hydrogen in silicon

Progress in the understanding of light‐ and elevated temperature‐induced degradation in silicon solar cells: A review

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