Experimental investigation of potential induced degradation of poly-crystalline photovoltaic modules: Influence of superstrate and encapsulant types

Potential induced degradation (PID) is amongst the most critical degradation phenomena affecting reliability of PV modules by causing power losses. In this research, PID was induced on PV modules in an environmental chamber in accelerated temperature and humidity conditions under the application of high voltage stress. The primary focus of this paper was to quantify the degradation extent of PV modules with different encapsulant and superstrate/glass types. The encapsulant types investigated were EVA and newly developed PVB. The superstrate types investigated were Soda-lime and Quartz. The progression and severity of degradation were determined through I-V measurements and EL imaging, revealing losses in Pmax and FF. The leakage current was measured during the PID test and no correlation between leakage current and power was observed. It was demonstrated that the PID loss was strongly dependent on the electrical and physical properties of the superstrate and encapsulant types. The module with quartz/EVA configuration experienced lower (17%) PID losses compared to the soda-lime/EVA module (32%). Similarly, the module with soda-lime/PVB configuration experienced lower (10%) PID losses compared to the soda-lime/EVA module (32%). While the module having both the quartz and PVB, exhibited the lowest PID progression with only 1% degradation in power.