Cathodoluminescence Spectrum Imaging Analysis of CdTe Thin-Film Bevels: Article No. 105704

John Moseley, Mowafak Al-Jassim, Harvey Guthrey, Richard Ahrenkiel, Wyatt Metzger, Joel Duenow, James Burst

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10 Scopus Citations

Abstract

We conducted T = 6 K cathodoluminescence (CL) spectrum imaging with a nanoscale electron beam on beveled surfaces of CdTe thin films at the critical stages of standard CdTe solar cell fabrication. We find that the through-thickness CL total intensity profiles are consistent with a reduction in grain-boundary recombination due to the CdCl2 treatment. The color-coded CL maps of the near-band-edge transitions indicate significant variations in the defect recombination activity at the micron and sub-micron scales within grains, from grain to grain, throughout the film depth, and between films with different processing histories. We estimated the grain-interior sulfur-alloying fraction in the interdiffused CdTe/CdS region of the CdCl2-treated films from a sample of 35 grains and found that it is not strongly correlated with CL intensity. A kinetic rate-equation model was used to simulate grain-boundary (GB) and grain-interior CL spectra. Simulations indicate that the large reduction in the exciton band intensity and relatively small decrease in the lower-energy band intensity at CdTe GBs or dislocations can be explained by an enhanced electron-hole non-radiative recombination rate at the deep GB or dislocation defects. Simulations also show that higher GB concentrations of donors and/or acceptors can increase the lower-energy band intensity, while slightly decreasing the exciton band intensity.
Original languageAmerican English
Number of pages8
JournalJournal of Applied Physics
Volume120
Issue number10
DOIs
StatePublished - 2016

NREL Publication Number

  • NREL/JA-5K00-66565

Keywords

  • catholuminescence
  • dislocations
  • excitons
  • geographic information systems
  • II-VI semiconductors

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