Economic impacts and approaches to address hot-spot defects in photovoltaic devices

The topic of hotspots in solar cells has gained recent press [1], and is garnering a degree of industry attention due to the link between hotspots and module failure modes such as laminate damage (bubbles) or permanent localized cell degradation. Hotspot detection is not new to the industry, although the methods have improved considerably [2] as infrared cameras and analysis algorithms have increased in performance. Historically the focus of hotospot detection has been in R&D labs where priority is placed on detailed root cause analysis and resolution, and cost is a secondary issue. Recently, PV manufacturers have started to implement inline hotspot screening, both at cell and module test, with an emphasis on cost of ownership, measurement speed, and purpose-built features that screen for hotspots in a completely automated fashion. This paper describes a time-resolved thermography system designed for use in PV manufacturing for quality control, and outlines economic factors that are causing this type of cell screening to be introduced inline.