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Why and how to adapt PID testing for bifacial PV modules?

Recent research has shown that bifacial PV modules with a glass/glass packaging are prone to different PID mechanisms occurring simultaneously on the front and the rear side of the solar cell. With this in mind, researchers investigating the impact of PID on each side of the bifacial solar cell separately apply PID stress to one side of bifacial PV modules according to stress method (b) as described in the IEC TS 62804‐1, that is, contacting the surface with a conductive electrode. Yet, in this paper, we show that such practice of PID testing might result in an unintended development of an electric field between the environmental chamber and the nonstressed side of the solar cell. Through our experimental study, we reveal that this electric field results in unintended bifacial PID stress of bifacial solar cells, which goes along with misleading interpretations of the evolving PID mechanisms and susceptibility of bifacial PV modules. Next to the methodology concerns, we discuss three possible solutions to prevent such unintended PID mechanisms from occurring.