Feedstock Analysis and Qualification

Crystallisation from silicon feedstock
© Fraunhofer ISE

Crystallisation from silicon feedstock covering a wide quality range is a research focus within the silicon value chain.

We are developing a standardized procedure for chemical analysis of feedstock comprising various analytical methods which allow an initial estimate of the material's potential for solar cell processing. By dissolving the crystalline silicon in a solution and subsequent spectrometric investigation, dopant concentrations can be determined and metallic impurities analyzed. Impurity concentrations are measured on samples following crystallization and measurements are repeated after individual high temperature stages in the solar cell process.

Research priorities:

  • Impurity concentrations in feedstock materials
  • Standardized analysis of relevant impurities in UMG silicon
  • Changes in impurity concentrations after crystallization and solar cell process
  • Assessment of impurities with recombination activity based on analysis of charge carrier lifetimes on the wafer. Determination of interstitial iron concentration and light-induced degradation due to B-O complexes
  • Highly efficient solar cell process for multicrystalline silicon for silicon material characterization: Determination of efficiency potential and evaluation of optimum process parameters, in particular optimum temperature control

Laboratories and equipment:

  • Characterization of feedstock and crystallized material:
  • Optical emission spectrometry (ICP-OES)
  • Atomic absorption spectrometry (AAS)
  • Neutron activation analysis (NAA)
  • Measuring methods for determining electrical material quality:
  • PL imaging, CDI, MW-PCD, QSSPC, luminescence spectroscopy