Two-Dimensional Cadmium Chloride Nanosheets in Cadmium Telluride Solar Cells

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31 Scopus Citations

Abstract

In this study we make use of a liquid nitrogen-based thermomechanical cleavage technique and a surface analysis cluster tool to probe in detail the tin oxide/emitter interface at the front of completed CdTe solar cells. We show that this thermomechanical cleavage occurs within a few angstroms of the SnO2/emitter interface. An unexpectedly high concentration of chlorine at this interface, a20%, was determined from a calculation that assumed a uniform chlorine distribution. Angle-resolved X-ray photoelectron spectroscopy was used to further probe the structure of the chlorine-containing layer, revealing that both sides of the cleave location are covered by one-third of a unit cell of pure CdCl2, a thickness corresponding to about one Cl-Cd-Cl molecular layer. We interpret this result in the context of CdCl2 being a true layered material similar to transition-metal dichalcogenides. Exposing cleaved surfaces to water shows that this Cl-Cd-Cl trilayer is soluble, raising questions pertinent to cell reliability. Our work provides new and unanticipated details about the structure and chemistry of front surface interfaces and should prove important to improving materials, processes, and reliability of next-generation CdTe-based solar cells.

Original languageAmerican English
Pages (from-to)20561-20565
Number of pages5
JournalACS Applied Materials and Interfaces
Volume9
Issue number24
DOIs
StatePublished - 21 Jun 2017

Bibliographical note

Publisher Copyright:
© 2017 American Chemical Society.

NREL Publication Number

  • NREL/JA-5K00-68533

Keywords

  • cadmium chloride
  • cadmium telluride
  • nanosheets
  • solar cells
  • XPS

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