The average adhesional shear strength at silicon cell/EVA interface in damp-heat, acceleration-tested modules was ~27% of that measured in new modules. The average carbon concentration at the surface of samples extracted from acceleration tested modules was 15 atomic % or ~30% of that measured in new modules. Surface concentrations of sodium on Si-cell samples from the acceleration tested modules ranged from 4.9 to 22.0 atomic %while those of phosphorous ranged from 4.3 to 7.1 at. %. These are very high impurity concentrations. Often small concentrations of phosphorous were detected at the interface between titanium oxide antireflection coating and silicon cell. All the samples, that showed low surface concentrations of carbon, had low adhesive strengths. Moreover, high sodium and phosphorous concentrations always correlated with low adhesional strengths. There was clear evidence of a direct correlation between carbon concentration and adhesional strength and an inverse correlation between sodium and phosphorous concentrations and adhesional strength. Similar correlation has been observed, at FSEC, in earlier studies on field deployed PV modules
Florida Solar Energy Center and Dhere, Neelkanth, "Study Of Delamination In Acceleration Tested PV Modules" (2001). FSEC Energy Research Center®. 587.