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A round robin test was carried out in four PV laboratories to compare accelerated lifetime testing. Twenty commercial non-packaged CIGS solar cells of similar performance were spread and exposed to damp heat conditions (85 °C and 85% RH) for approximately 500 h. Their JV performance was monitored during the damp heat exposure. After the test, three of the labs reported average efficiency losses of 87 ± 4%, 89 ± 5% and 92 ± 1%, which are close to median degradation rates found in literature. A higher degradation rate (efficiency loss of 97 ± 3% after only 143 h) was observed in the fourth lab. This was attributed to a poorly designed ceiling window sealing, which caused liquid water pooling on the samples. After modifying the climate chamber, the experiment was repeated with similar samples and an efficiency loss of 72 ± 6% after 475 h was observed for this lab.

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.

The combination of increasing operational voltages beyond 1000 V in photovoltaic (PV) installations and the emergence of new PV technologies requires a critical assessment of the susceptibility to potential-induced degradation (PID). Since this failure mode can trigger significant and rapid power losses, it is considered among the most critical failure modes with a high financial impact. Insights in the physical mechanism of the performance loss and its driving factors are critical to develop adapted characterization methods and mitigation solutions. PID in p-type solar cells is triggered by sodium (Na) that diffuses into stacking faults of the silicon lattice, causing shunt paths through the pn-junction. In addition, it is hypothesised that for bifacialp-PERC solar cells positive charges, such as Na+, accumulate in/on the negatively charged AlOxrear passivation layer due to the potential difference between the glass and the rear cell surface. This significantly increases surface recombination. However, the degradation behaviour observed in bifacial monocrystallinep-PERC solar cells under PID stress from both sides (bifacial PID stress) does not match with just one of the degradation mechanisms. A comprehensive test matrix was carried out to understand the physical origin of PID in front emitter bifacialp-PERC solar cells in a glass/glass packaging. The results show that bifacialp-PERC solar cells under bifacial PID stress suffer from both shunting of the pn-junction and increased surface recombination at their rear side. Hereby, we prove that the glass/glass packaging in combination with bifacial solar cells can significantly increase the severity of PID.

Microwire arrays are a powerful tool for the exertion of localized thermal stress on cellular networks. Combining microwire arrays with a set of orthogonal axon-guiding microchannels on-chip allows for the positioning of neurites, as well as control over their polarity. In this paper, we present a new fabrication approach, based on standard clean room fabrication and sacrificial layer etching, for the integration of microwire arrays into neurite guiding structures. The system permits the application of strong temperature gradients, enabling localized thermal stimulation inside microchannels.