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

    IEEE journal of photovoltaics, 07/2016, Letnik: 6, Številka: 4
    Journal Article

    We identify two engineering solutions to mitigate light-induced degradation (LID) in p-type multicrystalline silicon passivated emitter and rear cells, including modification of metallization firing temperature and wafer quality. Lifetime measurements on etched-back samples confirm that LID has a strong bulk component. Spatially resolved lifetime maps indicate that the defects responsible for LID are dispersed ubiquitously across the wafer. Reversibility of LID upon low-temperature annealing suggests a low-activation-energy barrier inconsistent with precipitated impurity dissolution. Lifetime spectroscopy of the LID-affected state reveals an asymmetry of electron and hole capture cross sections of ~28.5, consistent with a deep-level donor point defect (e.g., interstitial Ti, interstitial Mo, substitutional W), charged nanoprecipitate, or charged structural defect, such as a dislocation. Finally, we explain two possible root causes of this LID, including 1) a point-defect complex involving a hydrogen atom and a deep-level donor and 2) configurational change of a point-defect complex involving fast-diffusing impurities.