New Product: Sensors Unlimited SWIR based cameras detect wafer defects and cell efficiencies

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  Sensors Unlimited Shortwave Infrared Solar Cell Inspection

Product Briefing Outline: Sensors Unlimited, part of Goodrich Corp., says that its high-resolution, shortwave infrared (SWIR) area and linescan cameras are being used to improve the manufacturing yield of photovoltaic cells. SWIR technology is well suited to monitor the quality of solar thin films, concentrated PV, and crystalline cells, to maximize efficiency of the solar cell manufacturing process through final assembly of the completed modules.

Problem: Inspection of solar wafers with SWIR permits detecting defects, hidden cracks or saw marks inside or on the opposite side of the wafer.

Solution: The InGaAs-based SWIR cameras, which operate between 0.9 to 1.7 microns, are ideal for inspecting silicon boules and wafers due to the material’s transparency beyond 1.2 microns.  The Goodrich cameras reveal voids in silicon boules, bricks, and ingots before they are sliced into wafers to produce mono- and multicrystalline solar cells.  They can also detect hidden cracks by mapping stress in raw wafers, finished cells, and thin-films made for solar electricity generating panels.  SWIR cameras can also spot saw marks on the opposite side of a silicon wafer and/or defects inside the material.  In addition, by applying forward bias to cells to generate electroluminescence, the SWIR cameras are used to gauge cell efficiency and uniformity.  This aids improvement of cell manufacturing processes, and aids matching cells with similar efficiencies for assembly into modules.  The latter step prevents the loss of energy from the stronger cells which would be lost in heating the inefficient cells.

Applications: Inspection of ingots, bare wafers, solar cells.

Platform: Both Goodrich linescan and area cameras can be used for photoluminescence inspection of photovoltaic solar cells. The area cameras provide convenient still images while the digital high-speed, 1024 pixel line cameras are ideal for providing higher resolution at lower cost when used with continuous production flow or with moving inspection stages.

Availability: Currently available.