Effect of Damp Heat Aging on Solder Interconnection Reliability and Photoluminescence Degradation of Polycrystalline Silicon Solar Cells for Solar‐Powered UAV Applications

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ABSTRACT Solar‐powered UAV (Unmanned Aerial Vehicle) demand reliable solder interconnections to provide an uninterrupted power supply during long‐term missions in the harsh environment. In this study, the impact of damp heat aging on the electrical reliability of solder connections and the photoluminescence (PL) response of polycrystalline Si solar cells was examined. A total of nine solar cell samples (three per alloy) were soldered with SnPb, SnCu, and SnAgCu solder alloys and subjected to damp heat aging at 85°C/85% RH for a maximum of 1000 h. Electrical resistance was obtained after 0, 200, 400, 600, 800, and 1000 h of aging, whereas PL was performed after 0, 200, 400, 600, and 1000 h. The highest increase of electrical resistance was observed for SnCu (8.0%), and the minimum increase (2.4%) was found for SnPb, that was non‐monotonic trend. SnAgCu exhibited the best electrical stability with an increase of 5.4% in resistance. The PL intensity reduced by up to 38% at 600 h and then somewhat recovered at 1000 h, while the PL peak position remained almost steady at ~1.13 eV, suggesting that the effect of damp heat aging was on carrier recombination instead of the silicon bandgap. In general, damp heat aging deteriorated the solder interconnections and the silicon absorber, which may limit the long‐term reliability of solar‐powered UAV systems. In summary, the results indicate that SnAgCu is a suitable solder alloy for long‐duration solar‐powered UAV applications.