Identification and Characterization of Performance Limiting Regions in Poly-Si Wafers Used for PV Cells: Preprint

Conference · Fri Jul 01 00:00:00 EDT 2011

OSTI ID:1018867

Guthrey, Harvey; Gorman, Brian; Al-Jassim, Mowafak

As demand for silicon photovoltaic (PV) material increases, so does the need for cost-effective feedstock and production methods that will allow enhanced penetration of silicon PV into the total energy market. The focus on cost minimization for production of polycrystalline silicon (poly-Si) PV has led to relaxed feedstock purity requirements, which has also introduced undesirable characteristicsinto cast poly-Si PV wafers. To produce cells with the highest possible conversion efficiencies, it is crucial to understand how reduced purity requirements and defects that are introduced through the casting process can impair minority carrier properties in poly-Si PV cells. This is only possible by using multiple characterization techniques that give macro-scale information (such as thespatial distribution of performance-limiting regions), as well as micro and nano-scale information about the structural and chemical nature of such performance-limiting regions. This study demonstrates the usefulness of combining multiple techniques to analyze performance-limiting regions in the poly-Si wafers that are used for PV cells. This is done by first identifying performance-limitingregions using macro-scale techniques including photoluminescence (PL) imaging, microwave photoconductive decay (uPCD), and reflectometry), then using smaller-scale techniques such as scanning electron microscopy (SEM), electron backscattered diffraction (EBSD), laser ablation inductively coupled mass spectrometry (LA-ICP-MS), cathodoluminescence (CL), and transmission electron microscopy (TEM)to understand the nature of such regions. This analysis shows that structural defects as well as metallic impurities are present in performance-limiting regions, which together act to decrease conversion efficiencies in poly-Si PV cells.

• Research Organization: National Renewable Energy Lab. (NREL), Golden, CO (United States)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE), Renewable Power Office. Solar Energy Technologies Office
• DOE Contract Number: AC36-08GO28308
• OSTI ID: 1018867
• Report Number(s): NREL/CP-5200-50645; TRN: US1103484
• Resource Relation: Conference: Presented at the 37th IEEE Photovoltaic Specialists Conference (PVSC 37), 19-24 June 2011, Seattle, Washington
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
36 MATERIALS SCIENCE
ABLATION
CASTING
CATHODOLUMINESCENCE
DECAY
DEFECTS
DIFFRACTION
ELECTRONS
IMPURITIES
LASERS
MARKET
MASS SPECTROSCOPY
MINIMIZATION
PERFORMANCE
PHOTOLUMINESCENCE
PRODUCTION
SCANNING ELECTRON MICROSCOPY
SILICON
SPATIAL DISTRIBUTION
TRANSMISSION ELECTRON MICROSCOPY
silicon
PV
poly-Si
performance-limiting regions