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Polarization‐type potential‐induced degradation (PID‐p) of photovoltaic (PV) modules composed of n‐type interdigitated back contact (IBC) solar cells can decrease the performance of the PV modules under positive potential conditions. The purpose of this study is to observe and describe the reduction and stabilization of the electrical performance of every PV module installed in an operating PV system with the progress of the PID‐p over a time duration of 6 years. The direct current circuit of the investigated PV system is not grounded. Therefore, all the PV strings are under floating potential conditions. The results show that the performance of the n‐type IBC PV modules exhibits a two‐step degradation. In the first step of degradation, the PV performance at positive potential decreases with increasing the PV module potential, whereas the PV modules at negative potential show little performance degradation. The PV performance reduction due to PID‐p is mainly caused by the decreases in both open‐circuit voltage (VOC) and short circuit current (ISC). A PV performance reduction, which principally arises from the decrease in ISC, is observed at every PV module in the PV strings regardless of the PV module potential in the second step of degradation. Therefore, solar cell manufacturers who produce n‐type IBC, as well as those producing passivated emitters and rear totally diffused solar cells, are advised that processes to prevent the PID‐p are required. [ABSTRACT FROM AUTHOR]

Carrier distributions in monocrystalline silicon solar cells affected by potential-induced degradation (PID) were investigated using scanning nonlinear dielectric microscopy (SNDM), employing three samples with different PID levels. These observations clearly demonstrated that reductions in the carrier density were correlated with the extent of PID. Depth profile measurements showed that the solar cells were affected by PID to a significant depth of approximately 90 μm, equal to almost half the cell thickness. This result suggests that the Na+ migration is readily induced by the application of a high voltage. Super-higher-order-SNDM was also employed to obtain a more precise analysis of the depletion layer distributions in monocrystalline silicon solar cells with and without the application of a high voltage. The data showed that the depletion layer of a sample without PID was thinner than that of a sample exhibiting PID, indicating that the carrier concentration in the former sample was higher. This finding was in good agreement with the results produced by direct quantitative dopant measurements using SNDM. [ABSTRACT FROM AUTHOR]

Potential-induced degradation (PID) in photovoltaic (PV) modules based on n-type single crystalline Si solar cell (front junction cell) was experimentally generated by applying negative voltage from an Al plate, which was attached on the front cover glass of the module, to the Si cell. The solar energy-to-electricity conversion efficiency of the standard n-type Si PV module decreased from 17.8% to 15.1% by applying −1000 V at 85 °C for 2 h. The external quantum efficiency in the range from 400 to 600 nm significantly decreased after the PID test, although no change was observed from 800 to 1100 nm. PID in n-type Si PV modules can be basically explained by enhanced front surface recombination between electron and hole on the Si cell, whereas the polarity of voltage leading to PID depends on structure of Si cell. An ionomer encapsulant instead of EVA has significantly suppressed PID in n-type Si PV modules. [ABSTRACT FROM AUTHOR]

• PID delay effect by UV light in the 300–390 nm wavelength range was investigated. • The shorter wavelength UV light causes the PID delay effect more effectively. • The SiNx conductivity increase under UV light as a PID delay effect mechanism. • The PID delay effect was analyzed by a μ-PCD technique. A mechanism of potential induced degradation (PID) delay effect by ultraviolet (UV) light irradiation during PID test for p-type crystalline silicon (c-Si) solar cells was proposed in this work. The degradation rate of the solar cell performances is slowed down by the UV light irradiation in the 300–390 nm wavelength range during PID test. The conductivity increase of the silicon nitride (SiN x) anti-reflection coating (ARC) layer on the solar cell surface under UV light irradiation during PID tests, which relates to the mechanism preventing the penetration of sodium ions into the active cell layer, induces the PID delay effect for the p-type c-Si solar cells. The PID delay effect was also analyzed by a microwave photo-conductance decay (μ-PCD) technique in this work. The reduction behavior of the components in the μ-PCD signal curves including rapid (τ 1) and slow (τ 2) decay time constants and the effective lifetime (τ eff) presents a good correlation with the performance degradation behavior of the solar cells over PID test duration. Moreover, the reduction rate of these components is also slowed down under the UV light irradiation in the 300–390 nm wavelength range during PID tests. Notably, their reduction behavior was compatible with the mechanism of the conductivity increase of the SiN x ARC layer under UV light irradiation. [ABSTRACT FROM AUTHOR]

• PID tests for crystalline Si photovoltaic modules without front cover glass and using cells with various electrode pastes of controlled additive contents were performed. • This phenomenon is similar to that induced by Na in the front cover glass, but, it requires the shorter time duration as compared with the case of Na in the front cover glass. • In addition, it is found that Li in the paste also causes the PID equivalent to that by Na in the paste. Sodium (Na) and lithium (Li) in the silver (Ag) paste cause the potential-induced degradation (PID), while the PID of p-type crystalline silicon (Si) photovoltaic modules is caused by Na in the front cover glass. Some Ag pastes contain these elements to control the firing properties in solar cells fabrication. In order to eliminate the effect of Na and other elements in the front cover glass on PID, PID tests for crystalline Si photovoltaic modules without front cover glass and using cells with various electrode pastes of controlled additive contents were performed. When the Ag paste with Na is used, the shunt resistance decreases and the PID occurs. This phenomenon is similar to that induced by Na in the front cover glass, but, it requires the shorter time duration as compared with the case of Na in the front cover glass. In addition, it is found that Li in the paste also causes the PID equivalent to that by Na in the paste. [ABSTRACT FROM AUTHOR]

Potential-induced degradation (PID) in photovoltaic (PV) modules based on n-type single-crystalline Si solar cells (a bifacial cell, interdigitated back contact cells, and a hetero junction (HJ) cell) was experimentally investigated by applying high voltages to the modules. The power output of a PV module with an n-type bifacial-front junction (FJ) Si solar cell decreased by about 17% by applying −1000 V at 85 °C for 10 min, whereas no degradation was observed by applying +1000 V at 85 °C for 10 min. The spectrum of external quantum efficiency and transient absorption kinetics of the module after PID tests indicated that surface charge recombination between electron and hole on the Si cell was enhanced. PID in n-type Si PV modules can be approximately explained by surface polarization enhancing front surface recombination on Si cells, which corresponds to a loss of passivation effect by a silicon nitride (SiN x ) layer. On the other hand, no PID was observed in a PV module with an n-type bifacial-rear junction (RJ) Si solar cell and a commercial PV module based on an HJ cell by applying both positive and negative voltages. High conductive layers of transparent conductive oxide (TCO) on the top of HJ Si solar cells would significantly effective to suppress PID in n-type Si PV modules. [ABSTRACT FROM AUTHOR]

We perform indoor and outdoor potential-induced degradation (PID) tests for n-type front-emitter (n-FE) crystalline Si (c-Si) photovoltaic (PV) modules and compare their results. The indoor/outdoor acceleration factor for the polarization-type PID (PID-p) of n-FE PV modules is found to be ∼1000 at an indoor test temperature of 85 °C. We observe the progression of the PID-p of n-FE PV modules in rainy days, while their performance is recovered in sunny days. This may be because of the formation of a water film on a module surface acting as a conductive film, resulting in a larger electric field near the n-FE cells in rainy days. The recovery of the PV performance of n-FE modules in sunny days can partly explain the large acceleration factor for the indoor PID test against the outdoor test. • We performed indoor and outdoor PID tests for n-FE PV modules. • n-FE PV modules show polarization-type PID (PID-p) both indoors and outdoors. • The acceleration factor for the PID-p is ∼1000 at an indoor test temperature of 85 °C. • We observe the recovery of PID-p for the outdoor modules in sunny days. • The recovery may be one of the reasons for the large acceleration factor. [ABSTRACT FROM AUTHOR]

System voltages can cause significant degradation in photovoltaic modules. Polarization-type potential-induced degradation (PID) is accompanied by decreases in the short-circuit current density and the open-circuit voltage. The system voltage causes a polarization and surface charge accumulation, increasing the interface recombination. The surface passivation and the emitter doping concentration and gradient are considered to have large impacts. However, a systematic study on these effects has not yet been performed. In this paper, the effects of the front surface structure of n-type passivated emitter and rear totally diffused cell modules were investigated by accelerated PID tests. Standard cells with thin silicon dioxide/80-nm silicon nitride (SiN x) antireflection/passivation layers, refractive index (RI) of 2.0, exhibited typical polarization-type PID. Cells with increased RI = 2.4 for the bottom 20-nm SiN x showed no degradation at all. This may be caused by reduced charge accumulation in the SiN x layer near the interface due to the higher electrical conductivity of the Si-rich bottom layer. Secondly, cells with both a highly distorted interface, due to nitrogen insertion in the silicon surface, and an emitter with a high surface doping concentration have excellent resistance to PID. Cells with either the highly distorted interface or the higher emitter-surface doping concentration show no to minor improved resistance to PID. These findings improve the understanding of the effects of the front surface structure of cells on the polarization-type PID and may contribute to the implementation of these measures to reduce PID. • This study focused on the effects of the surface passivation configuration and the emitter-surface doping concentration of front-emitter, n-type crystalline silicon photovoltaic modules on their potential-induced degradation. • Cells with stacked SiN x layers composed of a 60-nm top layer with a refractive index of 2.0 and a 20-nm interlayer with refractive index of 2.4 showed no degradation. • Cells with both a distorted interface and surface-etched emitter that has a high surface doping concentration were confirmed to exhibit excellent resistance to potential-induced degradation. • These findings improve the understanding of polarization-type PID and contribute to the implementation of these measures to prevent the PID. [ABSTRACT FROM AUTHOR]

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 sc). After the first-stage degradation, the rear-emitter SHJ PV modules exhibited subsequent degradation characterized by a significant reduction in the J sc and open-circuit voltage (V oc), 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 sc and V oc. 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 sc and V oc 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. • Potential-induced degradation behaviors were compared of rear- and front-emitter silicon heterojunction PV modules. • Both modules showed the first-stage degradation with the same behavior characterized by a J sc reduction. • The rear-emitter modules showed the second-stage degradation characterized by significant reductions in J sc and V oc. • The front-emitter ones, on the other hand, showed degradation in FF together with moderate reductions in J sc and V oc. [ABSTRACT FROM AUTHOR]