Imaging CdCl2 Defect Passivation and Formation in Polycrystalline CdTe Films by Cathodoluminescence

Thomas Bidaud, John Moseley, Mahisha Amarasinghe, Mowafak Al-Jassim, Wyatt K. Metzger, Stéphane Collin

Research output: Contribution to journalArticlepeer-review

8 Scopus Citations


Polycrystalline thin-film solar cells are attractive for low-cost photovoltaics, but their efficiencies are hindered by material quality issues. State-of-the-art CdTe solar cells use CdCl2 annealing treatments whose effects are still being discovered at a fundamental level. Here, a series of CdTe samples with different annealing temperatures is investigated with high-resolution hyperspectral cathodoluminescence mapping measured at both room temperature and low temperature on the same microscopic areas. A statistical analysis over a large number of grains is combined with a local analysis at grain boundaries. The results elucidate the dynamic interplay between grain boundary and intragrain defect passivation and formation, in the midst of grain growth. The CdCl2 annealing initially contributes to an increase of the grain size and the passivation of both grain boundaries and grain interiors, increasing the overall luminescence and diffusion length. For higher annealing temperatures, a further increase of grain size is counterbalanced by the rise of bulk defects. The results illustrate the tradeoffs that lead to an optimal annealing temperature, as well as new methods for understanding defect passivation and creation in thin film solar cells.

Original languageAmerican English
Article number064601
Number of pages9
JournalPhysical Review Materials
Issue number6
StatePublished - Jun 2021

Bibliographical note

Publisher Copyright:
© 2021 American Physical Society.

NREL Publication Number

  • NREL/JA-5K00-77479


  • cathodoluminescence
  • defects
  • grain boundaries
  • passivation
  • thin film solar cells


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