Synchrotron-based analysis of chromium distributions in multicrystalline silicon for solar cells

Chromium (Cr) can degrade silicon wafer-based solar cell efficiencies at concentrations as low as 1010 cm−3. In this contribution, we employ synchrotron-based X-ray fluorescence microscopy to study chromium distributions in multicrystalline silicon in as-grown material and after phosphorous diffusion. We complement quantified precipitate size and spatial distribution with interstitial Cr concentration and minority carrier lifetime measurements to provide insight into chromium gettering kinetics and offer suggestions for minimizing the device impacts of chromium. We observe that Cr-rich precipitates in as-grown material are generally smaller than iron-rich precipitates and that Cri point defects account for only one-half of the total Cr in the as-grown material. This observation is consistent with previous hypotheses that Cr transport and CrSi2 growth are more strongly diffusion-limited during ingot cooling. We apply two phosphorous diffusion gettering profiles that both increase minority carrier lifetime ...

[1]  G. Hahn,et al.  Investigation of Lifetime-Limiting Defects After High-Temperature Phosphorus Diffusion in High-Iron-Content Multicrystalline Silicon , 2014, IEEE Journal of Photovoltaics.

[2]  D. Macdonald,et al.  Carrier de-smearing of photoluminescence images on silicon wafers using the continuity equation , 2013 .

[3]  Thorsten Dullweber,et al.  Impurity-related limitations of next-generation industrial silicon solar cells , 2013, 2012 IEEE 38th Photovoltaic Specialists Conference (PVSC) PART 2.

[4]  G. Coletti,et al.  Sensitivity of state‐of‐the‐art and high efficiency crystalline silicon solar cells to metal impurities , 2013 .

[5]  B. Lai,et al.  Precipitated iron: A limit on gettering efficacy in multicrystalline silicon , 2013 .

[6]  D. Macdonald,et al.  On the method of photoluminescence spectral intensity ratio imaging of silicon bricks: Advances and limitations , 2012 .

[7]  M. Schubert,et al.  Chromium distribution in multicrystalline silicon: comparison of simulations and experiments , 2012 .

[8]  T. Buonassisi,et al.  Impurity‐to‐efficiency simulator: predictive simulation of silicon solar cell performance based on iron content and distribution , 2011 .

[9]  M. Schubert,et al.  Understanding the distribution of iron in multicrystalline silicon after emitter formation: Theoretical model and experiments , 2011 .

[10]  K. Wambach,et al.  Impact of Metal Contamination in Silicon Solar Cells , 2010 .

[11]  M. Schubert,et al.  Imaging of chromium point defects in p-type silicon , 2010 .

[12]  Antonio Luque,et al.  Acceptable contamination levels in solar grade silicon: From feedstock to solar cell , 2009 .

[13]  H. Savin,et al.  Modeling phosphorus diffusion gettering of iron in single crystal silicon , 2009 .

[14]  K. Bothe,et al.  Photoconductance‐calibrated photoluminescence lifetime imaging of crystalline silicon , 2008 .

[15]  J. Kalejs,et al.  SIMS analysis of chromium gettering in crystalline silicon , 2008 .

[16]  Wilhelm Warta,et al.  Diffusion lengths of silicon solar cells from luminescence images , 2007 .

[17]  M. Pickett,et al.  Metal precipitation at grain boundaries in silicon: Dependence on grain boundary character and dislocation decoration , 2006 .

[18]  A. Holt,et al.  Gettering of transition metal impurities during phosphorus emitter diffusion in multicrystalline silicon solar cell processing , 2006 .

[19]  Matthew D. Pickett,et al.  Chemical natures and distributions of metal impurities in multicrystalline silicon materials , 2005 .

[20]  Eicke R. Weber,et al.  Synchrotron-based investigations of the nature and impact of iron contamination in multicrystalline silicon solar cells , 2005 .

[21]  D. Macdonald,et al.  Transition-metal profiles in a multicrystalline silicon ingot , 2005 .

[22]  D. Macdonald,et al.  Phosphorus gettering in multicrystalline silicon studied by neutron activation analysis , 2002, Conference Record of the Twenty-Ninth IEEE Photovoltaic Specialists Conference, 2002..

[23]  Stuart A. Maloy,et al.  Elastic properties of C40 transition metal disilicides , 1996 .

[24]  D. Schroder,et al.  Physical and electrical investigation of silicide precipitates in EFG polycrystalline silicon intentionally contaminated with chromium , 1990, IEEE Conference on Photovoltaic Specialists.

[25]  Pierre Villars,et al.  Pearson's handbook of crystallographic data for intermetallic phases , 1985 .

[26]  J.R. Davis,et al.  Impurities in silicon solar cells , 1980, IEEE Transactions on Electron Devices.

[27]  W. Read,et al.  Statistics of the Recombinations of Holes and Electrons , 1952 .

[28]  R. Hall.  Electron-Hole Recombination in Germanium , 1952 .

[29]  D. Macdonald,et al.  Understanding the distribution of iron in multicrystalline silicon after emitter formation : Theoretical model and experiments , 2015 .

[30]  Evan Franklin,et al.  The Impact of Silicon CCD Photon Spread on Quantitative Analyses of Luminescence Images , 2014, IEEE Journal of Photovoltaics.

[31]  M. Schubert,et al.  Interstitial Chromium in Silicon on the Micron Scale , 2013 .

[32]  M. Schubert,et al.  Analyses of the Evolution of Iron-Silicide Precipitates in Multicrystalline Silicon During Solar Cell Processing , 2013, IEEE Journal of Photovoltaics.

[33]  W. Warta,et al.  Imaging of Metastable Defects in Silicon , 2011, IEEE Journal of Photovoltaics.