Interpretation of laser scans from thin-film polycrystalline photovoltaic modules

Laser scanning of photovoltaic devices and modules with submillimeter resolution can provide valuable information about localized defects and cell-to-cell variations in response. There are, however, sources of possible errors, or artifacts, in interpretation that must be addressed, especially when series-connected solar cells are scanned. These issues are addressed for thin film CdTe and CuInSe₂ (CIS) PV modules and cells using a recently developed computer-controlled large-scale laser scanner at the National Renewable Energy Laboratory (NREL). This instrument was designed to serve as a tool for research, device and module quality control, and module failure analysis. The thrust of the report is twofold: (i) the development of reliable submillimeter module characterization techniques and analysis; and (ii) present the results of such techniques as applied to thin film CdTe and CIS modules