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Investigation of State Change of Finger Metallization due to Corrosion in Crystalline Silicon Photovoltaic Module
T. Semba
Degradation, Durability, Damp Heat (DH), Glass Frit, front side metallization
Photovoltaic Modules and BoS Components
Subtopic: PV Module Design, Manufacture, Performance and Reliability
Event: 36th European Photovoltaic Solar Energy Conference and Exhibition
Session: 4AV.2.58
1257 - 1260
ISBN: 3-936338-60-4
Paper DOI: 10.4229/EUPVSEC20192019-4AV.2.58
0,00 EUR
Document(s): paper


Among modules that degrade in the high temperature and high humidity test, there is an increase in the generation of dark areas in electroluminescence images from the vicinity of the bus bars due to the corrosion of the finger metallization. In order to understand the corrosion phenomenon of the metallization of the module, a high temperature and high humidity test was conducted using 3 photovoltaic modules made with glass, ethylene-vinyl acetate (EVA) encapsulant, solar cell, EVA, and backsheet structure (Module 1, 2, and 3), and the state of finger bars was observed with a scanning electron microscope (SEM). The three modules were ended one by one at 1500, 2500, and 3000 h from the start of the test. Modules degraded in electrical characteristics from the test time of 2500 h and the EL dark areas occurred. In addition, the EL dark area further expanded with increasing test time. The change of the state of the metallization seen by SEM observation resulted in the formation of voids at a part of the metallization from 1500 h in Module 1, and a gap at the interface of the bulk Ag and the glass layer at 2500 h. The decrease in electrical characteristics is considered to be an increase in contact resistance due to the occurrence of a gap from 2500 h in Module 2. On the other hand, in the module in which EVA encapsulant and glass were not used on the front side of the solar cell (Module 4), the degradation of the electrical characteristics in the high temperature and high humidity test was not confirmed. It was suggested that EVA is related to corrosion of the front side metallization even in the module where the EL dark area spreads from the bus bars in the high-temperature and high-humidity test.