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SUMMARY:Characterization of silicon photovoltaic wafers using polarized in
 frared imaging and discrete dislocation modeling
DTSTART:20150428T131500
DTEND:20150428T141500
DTSTAMP:20260917T025019Z
UID:e6c9db1fb109ba6fdb4bc91c2405208daf825b7dabeb0af45c77a111
CATEGORIES:Conferences - Seminars
DESCRIPTION:Harley T. Johnson\, Dpt of Mechanical Science and EngineeringU
 niversity of Illinois\, USA\nBio : Harley T. Johnson is a Professor in the
  Department of Mechanical Science and Engineering at the University of Ill
 inois at Urbana-Champaign\, and\, during the 2014-2015 academic year\, a F
 ulbright U.S. Scholar in France and Invited Professor at the Université J
 oseph Fourier in Grenoble.  Professor Johnson has research interests in t
 he mechanics and physics of electronic and optical materials.  He holds g
 raduate degrees from Brown University\, and an undergraduate degree from G
 eorgia Tech.  Among his professional distinctions\, he is a fellow of ASM
 E\, a recipient of an NSF CAREER Award\, and he has received the ASME Thom
 as J. R. Hughes Young Investigator Award for Special Achievement in Applie
 d Mechanics.\nAbstract : Silicon photovoltaic (PV) wafers contain dislocat
 ion structures that can cause severe solar cell device reliability problem
 s.  Photoluminescence imaging is a standard industry characterization met
 hod\, but infrared photoelasticity and other polarization-based methods ar
 e emerging as alternative nondestructive characterization techniques with 
 the ability to image both wafer-scale and dislocation-scale stress fields.
   While these methods can reveal significant qualitative detail about dis
 location structures\, they must be matched with theoretical analysis in or
 der to achieve quantitative understanding of stressed defects in the wafer
 s.  Here we combine our own lock-in infrared photoelastic imaging methods
  with discrete dislocation modeling in order to quantitatively study dislo
 cation structures in silicon PV wafers.  We present an isotropic elastic 
 superposition approach\, in which finite element solution of image stress 
 fields – including both dislocation and thermal residual image stresses 
 – are combined with analytical singular dislocation fields.  Thus\, the
  full linear elastic boundary value problem is solved and a simulated phot
 oelastic image is obtained.  Separately\, we use a dynamic discrete dislo
 cation approach to simulate the evolution of dislocation structures in the
  wafer.  In both the static and dynamic calculations\, the observed dislo
 cation structures are consistent with the experimental photoelastic images
 \, and the combination of methods makes it possible to classify the nature
  of the defects present.  Finally\, we show new results of polarized defe
 ct-band photoluminescence imaging\, a method with the potential to fully d
 iscriminate between regions of screw and 60 degree dislocations in PV sili
 con. Together\, these methods allow us to understand the effects of disloc
 ations on both mechanical and optoelectronic reliability in these systems.
LOCATION:ME B3 31 http://plan.epfl.ch/?room=MEB331
STATUS:CONFIRMED
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