System performance loss due to LeTID

Kersten, F.; Fertig, Fabian; Petter, K.; Klöter, B.; Herzog, Evelyn; Strobel, Matthias; Heitmann, Johannes; Müller, Jörg

doi:10.1016/j.egypro.2017.09.260

Cited by 64 publications

(32 citation statements)

References 14 publications

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“…The LeTID defect is formed and the system moves into the degraded state B by carrier injection at temperatures above an apparent "threshold temperature" T thr of around 50-60°C severely decreasing the carrier lifetime to values as low as several tens of microseconds. Hence, with regard to (PERC) modules, significant performance losses can be expected especially in warm, sunny regions if no counter measures are taken [5]. Upon prolonged exposure to degradation conditions, the system reaches the regenerated state C in which the LeTID defect appears to be permanently deactivated.…”

mentioning

confidence: 99%

Temporary Recovery of the Defect Responsible for Light- and Elevated Temperature-Induced Degradation: Insights Into the Physical Mechanisms Behind LeTID

Kwapil

Schön

Niewelt

et al. 2020

IEEE J. Photovoltaics

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The effect of light-and elevated temperature-induced degradation (LeTID) can be nonpermanently reversed by charge carrier injection below the degradation temperature (commonly used degradation temperatures are above ∼70°C). In this study, we show that the rate of temporary recovery depends strongly on the excess carrier density. We observe that the order of the reaction changes from pseudo-zero to first with increasing injection. The rate decreases slightly with increasing temperature. Since the samples can go through multiple degradation/recovery cycles without distinct changes in the degradation kinetics, the experimentally accessible recovered and degraded states are interpreted as manifestations of the equilibrium concentrations of the defect responsible for LeTID at different temperatures. Based on our observations, we argue that the process underlying LeTID degradation is the dissociation of a precursor rather than an association of two or more components. In light of the relation between LeTID susceptibility and bulk hydrogen concentration, we hypothesize that the LeTID precursor dissociates into the LeTID defect and monatomic hydrogen. Numerical simulations of the coupled rate equations including hydrogen interactions well reproduce the experimental observations; according to these results, the presence of a sink for the atomic hydrogen such as dopant atoms is paramount for the LeTID degradation. Index Terms-Degradation, Defect reactions, light-and elevated temperature-induced degradation (LeTID), model, silicon defects. I. INTRODUCTION A FTER the first description of the phenomenon later termed light-and elevated temperature-induced degradation (LeTID) [1], extensive research has been conducted on the influences determining the LeTID extent and kinetics. Noting the

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confidence: 99%

Temporary Recovery of the Defect Responsible for Light- and Elevated Temperature-Induced Degradation: Insights Into the Physical Mechanisms Behind LeTID

Kwapil

Schön

Niewelt

et al. 2020

IEEE J. Photovoltaics

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“…In this study, the useful life is defined as the non-reversible performance loss, such that the module or system power decreases by 20% of the "maximum stable power" measured in the field. The notion of a maximum stable power is introduced to separate long-term degradation from early stage degradation events such as light-induced degradation (LID) for p-type crystalline silicon modules 13 or light-and elevated temperatureinduced degradation for multicrystalline silicon and passivated emitter and rear cell (PERC) 16,17 modules. It also helps to separate other reversible effects reducing module performance such as soiling 18 and seasonal variations.…”

Section: Ft and Rul Definitionsmentioning

confidence: 99%

“…The lize gradually or undergo a regeneration phase. 16,17 If a regeneration phase is detected, we recommend to eliminate the data until the onset of this phase.…”

Section: Data Filteringmentioning

confidence: 99%

Photovoltaic lifetime forecast model based on degradation patterns

Kaaya

Lindig

Weiß

et al. 2020

Progress in Photovoltaics

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The ever‐growing secondary market of photovoltaic (PV) systems (i.e., the transaction of solar plants ownership) calls for reliable and high‐quality long‐term PV degradation forecasts to mitigate the financial risks. However, when long‐term PV performance degradation forecasts are required after a short time with limited degradation history, the existing physical and data‐driven methods often provide unrealistic degradation scenarios. Therefore, we present a new data‐driven method to forecast PV lifetime after a small performance degradation of only 3%. To achieve an accurate and reliable forecast, the developed method addresses the fundamental challenges that usually affect long‐term degradation evaluation such as data treatment, choosing a good degradation model, and understanding the different degradation patterns. In the paper, we propose and describe an algorithm for degradation trend evaluation, a new concept of multiple “time‐ and degradation pattern‐dependent” degradation factors. The proposed method has been calibrated and validated using different PV modules and systems data of 5 to 35 years of field exposure. The model has been benchmarked against existing statistical models evaluating 11 experimental PV systems with different technologies. The key advantage of our model over statistical ones is the ability to perform more reliable forecasts with limited degradation history. With an average relative uncertainty of 7.0%, our model is outstanding in consistency for different forecasting time horizons. Moreover, the model is applicable to all PV technologies. The proposed method will aid in making reliable financial decisions and also in adequately planning operation and maintenance activities.

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“…traditional aluminium back surface field (Al-BSF) cells. Degradation in PERC cells has indeed been shown for light and elevated temperature induced degradation (LeTID) [2,3] and boron-oxygen LID (BO-LID) [4][5][6], but it has not yet been shown for copper-related LID (Cu-LID) on Cz-Si substrates.…”

Section: Introductionmentioning

confidence: 99%

Impact of copper on light-induced degradation in Czochralski silicon PERC solar cells

Modanese

Wagner

Wolny

et al. 2018

Solar Energy Materials and Solar Cells

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Both multicrystalline and Czochralski (Cz) silicon substrates are known to suffer from various mechanisms of light-induced degradation (LID), including copper-related LID (Cu-LID). Past studies on Cu-LID have mostly been performed on unprocessed wafers, omitting the impact of the solar cell process on the copper distribution. Here, we carefully contaminate Cz-substrates of different quality with different amounts of copper and process the substrates into complete industrial Cz-Si PERC solar cells, reaching a comprehensive mapping of the impact of Cu-LID for the PV industry. The results show that both the copper contamination level and Cz crystal quality are critical factors affecting the extent of Cu-LID. Most importantly, we show that copper can result in significant concentrations in the bulk of the finished PERC cells after being exposed to only trace surface contamination. Consequently, even a small local copper contamination area (~ 3-4 cm 2) is sufficient to induce strong LID in the full-sized (156×156 mm 2) cell parameters, resulting e.g. in ~7% relative efficiency loss during light soaking. The corresponding short circuit current density decreases by up to a factor of two in the contaminated areas.

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System performance loss due to LeTID

Cited by 64 publications

References 14 publications

Temporary Recovery of the Defect Responsible for Light- and Elevated Temperature-Induced Degradation: Insights Into the Physical Mechanisms Behind LeTID

Temporary Recovery of the Defect Responsible for Light- and Elevated Temperature-Induced Degradation: Insights Into the Physical Mechanisms Behind LeTID

Photovoltaic lifetime forecast model based on degradation patterns

Impact of copper on light-induced degradation in Czochralski silicon PERC solar cells

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