A Comparison of Simultaneous Degradations in Silicon Solar Cells under UV Weathering Conditions

We investigate test procedures to elucidate mechanisms of ultraviolet (UV) light-induced degradation on modern photovoltaic (PV) cell technologies. We compare commercial silicon PV cells weathered with a daylight filtered xenon source that includes UV and visible light, and under similar temperature/humidity conditions in the dark- where other simultaneously occurring degradation modes may instead dominate. Under xenon UV + Vis irradiation, we compare aging under open- and short-circuit bias conditions. We also weather cells under UVA-340 fluorescent tube irradiation under short- circuit conditions. For PERC and SHJ cells aged under UV-Vis- light, we observe small (<3%) performance increase or decrease after 3000 hours of aging, depending on the cell, with no consistent trend on whether open- or short- circuit results in more degradation. Cells aged in the dark under similar humidity and temperature conditions do not significantly degrade, indicating any degradation in the PERC and SHJ cells is not primarily associated with moisture. However, one type of TOPCon cell suffered 5% power loss under 25% RH and 85 degrees C weathering, highlighting the need to control for moisture-sensitivity in these studies screening for UV susceptibility on unencapsulated cells. For SHJ and TOPCon cells aged under UV-only light, we observe a performance increase of +0.4% to +1% with subsequent sunlight exposure.