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Influences of both high-voltage stress and hygrothermal stress were studied for homojunction and heterojunction crystalline Si photovoltaic (PV) modules. In order to separately access the influence of these stresses, these PV modules were subjected to the sequential test with hygrothermal stress and high-voltage stress for various stress durations of each test. It was found that for p-type homojunction crystalline Si PV modules hygrothermal stress applied in advance much enhances potential-induced degradation (PID) by high-voltage stress. High-voltage stress applied in advance also accelerates finger-electrode degradation by hygrothermal stress. It was also clarified that hygrothermal stress for short duration applied in advance much enhances PID by high-voltage stress for n-type heterojunction crystalline Si PV modules. Possible mechanism for these accelerated degradation phenomena by combined stresses will be presented., identifier:https://dspace.jaist.ac.jp/dspace/handle/10119/18012

Potential-induced degradation (PID)-test results of modules fabricated from the rear- and front-emitter silicon heterojunction (SHJ) solar cells were compared to clarify the influence of the emitter position of SHJ photovoltaic (PV) cell modules on their PID behaviors. The PID tests were performed by applying a bias of −2000 V to the shorted interconnector ribbons from the front surface of the cover glass, at 85 °C. In the initial stage, both modules showed the same degradation characterized by a reduction in the short-circuit current density (J_). After the firststage degradation, the rear-emitter SHJ PV modules exhibited subsequent degradation characterized by a significant reduction in the J_ and open-circuit voltage (V_), due to the enhancement of the minority-carrier recombination in the front surface region of the n-type crystalline silicon base. The front-emitter SHJ PV modules, on the other hand, showed a reduction in the fill factor (FF), in addition to moderate reductions in J_ and V_. The FF reduction of the front-emitter SHJ PV modules is considered to be caused by the enhancement of the recombination in the front surface region of the n-type crystalline-silicon base as the region corresponds to the pn junction interface of the front-emitter configuration. The moderate reductions in both J_ and V_ may be due to further progression of the first-stage degradation. These findings are essential for understanding the mechanism of PID in SHJ PV cell modules., identifier:https://dspace.jaist.ac.jp/dspace/handle/10119/18072

We investigated the influence of backsheet materials on potential-induced degradation (PID) in n-type crystalline-silicon (c-Si) photovoltaic (PV) cell modules. Silicon heterojunction PV cell modules and rear-emitter n-type c-Si PV cell modules were fabricated by using aluminum backsheets composed of poly ethylene terephthalate (PET)/aluminum/PET as well as typical backsheets. PID tests of the modules were performed by applying a negative bias in a dry environment (<2% relative humidity). Regardless of the types of cells, the modules with the aluminum backsheets showed smaller degradation. This indicates that aluminum backsheets reduce PID effects, and to alter backsheets may be a potential measure to reduce PID., identifier:https://dspace.jaist.ac.jp/dspace/handle/10119/16959

Accelerated tests were used to study potential-induced degradation (PID) in photovoltaic (PV) modules fabricated from silicon heterojunction (SHJ) solar cells containing tungsten-doped indium oxide (IWO) transparent conductive films on both sides of the cells and a rear-side emitter. A negative bias of −1000 V was applied to a module with respect to the cover glass surface in a chamber maintained at 85 °C, which significantly reduced the cell’s short-circuit current density (J_) within several days. Based on dark current density–voltage and external quantum efficiency measurements, the reduction in the J_ was attributed to optical losses rather than carrier recombination. X-ray absorption fine structure spectroscopy showed the formation of metallic indium (In) in the IWO layers of a degraded cell, which suggests that the root cause of the optical loss was a darkening of the front IWO layers caused by the precipitation of metallic In. In extremely severe PID tests, the SHJ PV modules exhibited not only a further reduction in the J_ but also a moderate reduction in the open-circuit voltage (V_). These J_ and V_ reductions were probably caused by sodium being introduced into the base region of the cells. A comparison of the PID test results of the SHJ PV modules with those of other types of PV modules indicates that SHJ PV modules have a relatively high resistance to PID. As a module with an ionomer encapsulant exhibited little degradation, their high resistances to PID may be further improved by using encapsulants with high electrical resistances., identifier:https://dspace.jaist.ac.jp/dspace/handle/10119/16205