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Keywords:

  • CIGS;
  • ToF-SIMS;
  • quantitative;
  • depth profiling;
  • photovoltaics

In the process of optimizing solar cells, a quantitative and depth-resolved elemental analysis of photovoltaic thin films is strongly required. Regarding Cu(In,Ga)Se2 (CIGS) thin film solar cells, depth-dependent stoichometric changes of Ga and In are of great interest because the In/Ga ratio has a large effect on solar cell efficiencies. In this paper, we investigate the elemental composition of CIGS thin film solar cells based on secondary ion intensities in time-of-flight secondary ion mass spectrometry (ToF-SIMS) depth profiling, providing high sensitivities and high spatial resolution. Quantification of the data is obtained by comparison to X-ray photoelectron spectroscopy depth profiles. The detection of MCs+ clusters is used for semiquantitative elemental analysis of CIGS thin films. Correlation plots of the intensities of GaCs+ and InCs+ indicate that there is no relevant matrix effect for In and Ga due to changes in stoichiometry in the layer. Additional high-resolution inductively coupled plasma mass spectrometry measurements show a strong correlation between the ratio of the bulk concentrations of Ga and In and the ratio of integrated ToF-SIMS intensities of GaCs+ and InCs+ therefore supporting the quantitative interpretation of MCs+ data. Copyright © 2012 John Wiley & Sons, Ltd.