Light- and Elevated-Temperature-Induced Degradation-Affected Silicon Cells from a Utility-Scale Photovoltaic System Characterized by Deep-Level Transient Spectroscopy

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Abstract

Photovoltaic modules from a utility-scale field experienced power loss by light- and elevated-temperature-induced degradation (LeTID). Samples from the affected monocrystalline silicon cells are cored and extracted from the module packaging and then laser-scribed to form 2-mm diameter isolated areas. Using deep-level transient spectroscopy, a majority-carrier, hole-trap defect with an activation energy of 0.42 eV is detected on degraded and regenerated samples. The LeTID-degraded sample, however, has a larger signal corresponding to a trap density of 1.1 x 10 13 cm -3 , which is about five times larger than the 2.1 x 10 12 cm -3 trap density of the regenerated sample. An increase in filling pulse time from 50 u s to 20 ms shows a slight decrease in activation energy from 0.42 to 0.36 eV suggesting that the defect level may consist of a band of energy states where shallower states continue to fill with long filling times. The capture rate of the defect is directly measured using an increasing series of filling pulsewidths in 15 to 125 ns range. This leads to a measured capture cross section of 5.1 x 10 -17 cm 2 , and using an approximate defect density of 10 13 cm -3 , the majority-carrier-hole lifetime related to this defect is approximately 100 u s when in the LeTID-degraded state.
Original languageAmerican English
Pages (from-to)703-710
Number of pages8
JournalIEEE Journal of Photovoltaics
Volume12
Issue number3
DOIs
StatePublished - 1 May 2022

Bibliographical note

Publisher Copyright:
© 2011-2012 IEEE.

NREL Publication Number

  • NREL/JA-5K00-81714

Keywords

  • Charge carrier lifetime
  • degradation
  • laser ablation
  • photovoltaic cells
  • semiconductor impurities
  • solar panels

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