The role of sodium in photovoltaic devices under high voltage stress: A holistic approach to understand unsolved aspects

Colli, Alessandra

doi:10.1016/j.renene.2013.05.007

Cited by 17 publications

(6 citation statements)

References 20 publications

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“…After the exposure of a 50 V bias combined with 85 °C on CIGS solar cells, sodium migrated from the glass substrate to the pn‐junction, which resulted in a rapid decrease of the conversion efficiency. In this case, the high voltage bias was apparently able to drive sodium from the glass, leading to a potential‐induced‐degradation (PID) like process, which was also reported by Colli . At this moment, it is not yet possible to distinguish between the impact of sodium and potassium migration.…”

Section: Discussionmentioning

confidence: 52%

The impact of alkali elements on the degradation of CIGS solar cells

Theelen

Hans

Barreau

et al. 2015

Progress in Photovoltaics

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Unencapsulated CIGS solar cells with high and low contents of sodium (Na) and potassium (K) were simultaneously exposed to damp heat and illumination. The solar cells with a high alkali (Na, K) content exhibited higher initial conversion efficiencies, but degraded severely within 100 h, while the alkali poor samples kept relatively stable performance under damp heat and illumination. The degradation of the samples with a high alkali content resulted in the formation of sodium rich spots on the top ZnO:Al surface of the samples. This is likely caused by light-induced Na + migration via the grain boundaries in the absorber to the depletion region, where the Na + accumulated. This allowed subsequent Na + transport through the depletion region due to the lowering of the internal electric field caused both by the Na + accumulation and illumination. The migration resulted in the formation of shunt paths, which reduced the shunt resistance and open circuit voltage. Furthermore, ingression of water into the ZnO:Al is expected to be responsible for a slow but steady increase in series resistance for both high and low alkali solar cells. Additionally, sodium migration led to a severe increase of the series resistance in case of alkali rich samples.

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Section: Discussionmentioning

confidence: 52%

The impact of alkali elements on the degradation of CIGS solar cells

Theelen

Hans

Barreau

et al. 2015

Progress in Photovoltaics

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“…Electrochemical corrosion of transparent conductive oxide (TCO) related to negative potential was described in 1989 [11]. It is associated with Na + migration and the presence of moisture (from the extremities of the modules) accelerated as the trapped water vapor increases the electrical conductivity and the LC [3]. In order to avoid this phenomenon, thin-film manufacturers normally produce unframed modules to maximize the resistance of the LC path between the cells and the ground.…”

Section: Pid Reviewmentioning

confidence: 99%

“…In turn, the LC leads to the accumulation of a charge trapped on the active layer. Cells with a positive potential are affected by a negative charge, which is mainly made up of electrons; while cells with a negative potential are affected by a positive charge, which is mainly made up of Na + ions -for standard pbased cells-always present on the soda-lime glass front cover of the module [2], [3] and the composition of the anti-reflective coating (ARC). This is exactly the case in standard c-Si modules located at the negative pole of floating voltage arrays, which predominates in current PV-plant market.…”

Section: Introductionmentioning

confidence: 99%

In-the-field PID related experiences

Martínez‐Moreno

Figueiredo

Lorenzo

2018

Solar Energy Materials and Solar Cells

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Potential induced degradation could considerably decrease the performance of photovoltaic systems which operate at high DC voltages. Nonetheless, methodologies for dealing with it in field are not clearly yet defined. This work explains the kinetics of this phenomenon in the field and presents an assessment of its occurrence, detection and prediction in real PV installations. Measurements of the instantaneous operating voltages of the photovoltaic module as a verification routine and predictive maintenance is proposed here as a reasonable and most accurate way of analyzing the actual power losses of the photovoltaic system related to this kind of degradation, as well as detecting and predicting it. Potential induced degradation prevention and recovery have also been carried out by the application of reverse voltage during the night, showing the validity of this technique. A literature review for the PID dynamics of different kinds of photovoltaic cell technologies and development of PID test methodologies and standards is also presented.

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“…The pathway from the active layer to the frame through the front glass which has a high surface conductivity is the most dominant during the PID effect [16,17]. The low resistivity is mainly due to the encapsulant material: the soda-lime glass used in thin-film PV modules can be the source of sodium ions that, located at the front glass surface, might lead to a loss of the efficiency [18][19][20]. Even though the PID mechanism is not yet well understood, the sodium ions that migrate from the glass to the TCO seem to be one of the main reasons for the degradation [14].…”

Section: Introductionmentioning

confidence: 99%

Experimental Evidence of PID Effect on CIGS Photovoltaic Modules

et al. 2020

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As well known, potential induced degradation (PID) strongly decreases the performance of photovoltaic (PV) strings made of several crystalline silicon modules in hot and wet climates. In this paper, PID tests have been performed on commercial copper indium gallium selenide (CIGS) modules to investigate if this degradation may be remarkable also for CIGS technology. The tests have been conducted inside an environmental chamber where the temperature has been set to 85 °C and the relative humidity to 85%. A negative potential of 1000 V has been applied to the PV modules in different configurations. The results demonstrate that there is a degradation affecting the maximum power point and the fill factor of the current-voltage (I-V) curves. In fact, the measurement of the I-V curves at standard test condition show that all the parameters of the PV modules are influenced. This reveals that CIGS modules suffer PID under high negative voltage: this degradation occurs by different mechanisms, such as shunting, observed only in electroluminescence images of modules tested with negative bias. After the stress test, PID is partially recovered by applying a positive voltage of 1000 V and measuring the performance recovery of the degraded modules. The leakage currents flowing during the PID test in the chamber are measured with both positive and negative voltages; this analysis indicates a correlation between leakage current and power losses in case of negative potential.

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The role of sodium in photovoltaic devices under high voltage stress: A holistic approach to understand unsolved aspects

Cited by 17 publications

References 20 publications

The impact of alkali elements on the degradation of CIGS solar cells

The impact of alkali elements on the degradation of CIGS solar cells

In-the-field PID related experiences

Experimental Evidence of PID Effect on CIGS Photovoltaic Modules

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