Characterization of silicon photovoltaic wafers using polarized infrared imaging and discrete dislocation modeling
Event details
| Date | 28.04.2015 |
| Hour | 13:15 › 14:15 |
| Speaker |
Harley T. Johnson, Dpt of Mechanical Science and EngineeringUniversity of Illinois, USA Bio : Harley T. Johnson is a Professor in the Department of Mechanical Science and Engineering at the University of Illinois at Urbana-Champaign, and, during the 2014-2015 academic year, a Fulbright U.S. Scholar in France and Invited Professor at the Université Joseph Fourier in Grenoble. Professor Johnson has research interests in the mechanics and physics of electronic and optical materials. He holds graduate degrees from Brown University, and an undergraduate degree from Georgia Tech. Among his professional distinctions, he is a fellow of ASME, a recipient of an NSF CAREER Award, and he has received the ASME Thomas J. R. Hughes Young Investigator Award for Special Achievement in Applied Mechanics. |
| Location | |
| Category | Conferences - Seminars |
Abstract : Silicon photovoltaic (PV) wafers contain dislocation structures that can cause severe solar cell device reliability problems. Photoluminescence imaging is a standard industry characterization method, but infrared photoelasticity and other polarization-based methods are 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 dislocation structures, they must be matched with theoretical analysis in order to achieve quantitative understanding of stressed defects in the wafers. Here we combine our own lock-in infrared photoelastic imaging methods with discrete dislocation modeling in order to quantitatively study dislocation 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 photoelastic image is obtained. Separately, we use a dynamic discrete dislocation approach to simulate the evolution of dislocation structures in the wafer. In both the static and dynamic calculations, the observed dislocation 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 defect-band photoluminescence imaging, a method with the potential to fully discriminate between regions of screw and 60 degree dislocations in PV silicon. Together, these methods allow us to understand the effects of dislocations on both mechanical and optoelectronic reliability in these systems.
Practical information
- Informed public
- Free
- This event is internal
Organizer
- IGM-GE
Contact
- Géraldine Palaj