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

 
: Kwapil, W.; Schön, J.; Niewelt, T.; Schubert, M.C.

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Fulltext ()

IEEE Journal of Photovoltaics 10 (2020), No.6, pp.1591-1603
ISSN: 2156-3381
ISSN: 2156-3403
English
Journal Article, Electronic Publication
Fraunhofer ISE ()
Photovoltaik; degradation models; silicon solar cell; transient simulation; Silicium-Photovoltaik; Charakterisierung von Prozess- und Silicium-Materialien

Abstract
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.

: http://publica.fraunhofer.de/documents/N-618154.html