Experimental Evidence of PID Effect on CIGS Photovoltaic Modules

Abstract

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.

Potential induced degradation of CIGS PV systems: A literature review

“…This layer could be a metal plate or metal foil. Such tests were compared to more conventional PID testing by Boulhidja et al 13 They have confirmed that the power degradation of PV modules was noticeably higher when the high voltage application was on the aluminium plate placed on the back or front surface, in comparison to application on the frame only. The bias application on the back surface yielding the worst degradation effects.…”

“…For modules, studies mainly focus on tracking of the electrical properties upon PID stressing such as I-V characteristics and leakage current measurements. [13][14][15][16][17] Due to the size and the packaging of the field modules, with front and back glass sheets and the encapsulant, it is more difficult to study the nature of the defects and the root-cause of the degradation mechanisms with laboratory based analysis methods. In-depth microanalytic studies for PID have only been reported with laboratory-made CIGS samples, such as mini-modules or cell level samples.…”

“…However, there were reported cases where longer stress times resulted in overall poor I-V characteristics. 13,16,27,28 Fig. 5 shows representative J-V curves from a cell based study, where 50 V of bias was applied at 85 o C in air.…”

Using UAV to Detect Solar Module Fault Conditions of a Solar Power Farm with IR and Visual Image Analysis

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Mitigating Potential-Induced Degradation (PID) Using SiO2 ARC Layer

“…Experimental evidence of the PID effect on copper indium gallium selenide (CIGS) showed that CIGS PV cells suffer from PID testing [23]. The results showed that there is an almost 15% drop in the maximum output power after 120 h of PID testing.…”