Performance and Reliability Implications of Two-Dimensional Shading in Monolithic Thin-Film Photovoltaic Modules

Sourabh Dongaonkar, Chris Deline, Muhammad Ashraful Alam

Research output: Contribution to journalArticlepeer-review

36 Scopus Citations


We analyze the problem of partial shading in monolithically integrated thin-film photovoltaic (TFPV) modules, and explore how the shape and size of the shadows dictate their performance and reliability. We focus on the aspects of the shading problem unique to monolithic TFPV, arising from thin long rectangular series-connected cells, with partial shadows covering only a fraction of the cell area. Using calibrated 2-D circuit simulations, we show that due to the cell shape, the unshaded portion of partially shaded cell experiences higher heat dissipation due to redistribution of voltages and currents across the cells. We then use thermal imaging techniques to compare our results with module behavior under shade in realistic situations. We also analyze the effect of shadow size and orientation by considering several possible shading scenarios. We find that thin edge shadows can cause potentially catastrophic reverse bias damage, depending on their orientation. Finally, we show that external bypass diodes cannot protect the individual cells from shadow-induced reverse stress, but can limit the string output power loss for larger shadows.

Original languageAmerican English
Article number6558752
Pages (from-to)1367-1375
Number of pages9
JournalIEEE Journal of Photovoltaics
Issue number4
StatePublished - 2013

NREL Publication Number

  • NREL/JA-5200-60819


  • Bypass diodes
  • circuit simulation
  • module simulation
  • partial shading
  • reverse-bias stress
  • thin-film photovoltaic (PV)


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