Light and Elevated Temperature Induced Degradation (LeTID) in a Utility-Scale Photovoltaic System

Michael Deceglie, Timothy Silverman, Steven Johnston, James Rand, Mason Reed, Robert Flottemesch, Ingrid Repins

Research output: Contribution to journalArticlepeer-review

17 Scopus Citations


We present a detailed case study of degradation in monocrystalline silicon photovoltaic modules operating in a utility-scale power plant over the course of approximately three years. We present the results of degradation analysis on arrays within the site, and find that five of the six arrays degraded faster than the best performing array, even though the arrays consist of modules of the same manufacturer and model. We also describe the results of extensive laboratory characterization of modules returned from the field, including module- and cell-level current-voltage characterization, luminescence imaging, and accelerated testing. The laboratory test results and the field performance are consistent with light and elevated temperature induced degradation (LeTID). Notably, we observe differences in back contact technology between affected and unaffected modules. This article also demonstrates a method to identify possible LeTID degradation in the field and confirm the result with laboratory testing of a small number of modules.

Original languageAmerican English
Article number9097396
Pages (from-to)1084-1092
Number of pages9
JournalIEEE Journal of Photovoltaics
Issue number4
StatePublished - Jul 2020

Bibliographical note

Publisher Copyright:
© 2011-2012 IEEE.

NREL Publication Number

  • NREL/JA-5K00-75966


  • Degradation
  • light and elevated temperature induced degradation (LeTID)
  • open-source
  • photovoltaics (PV)
  • reliability


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