The performance and long-term stability of silicon concentrator solar cells immersed in dielectric liquids

Direct liquid-immersion cooling of concentrator solar cells was proposed as a solution for receiver thermal management of concentrating photovoltaic (CPV) systems. This research investigates the performance and long-term stability of silicon CPV solar cells operated in De-ionized (DI) water, isopropyl alcohol (IPA), dimethyl silicon oil, and ethyl acetate, respectively. Current–voltage characteristics of silicon CPV solar cells are measured. The presence of a thin liquid layer (1.5 mm) results in an increase in the silicon CPV solar cells efficiency by 8.5–15.2% from the reference value. With an increase of the liquid layer thickness above the cell surface up to 9 mm, due to more incident light is absorbed by the thicker liquid layer, the degree of the improvements to the cell efficiency decreases, which also depends to a noticeable degree on the liquid species. Further, more power output from the cells operated in liquids is achieved under higher concentration ratio. The long-term cell performance is discussed through three separate liquid immersion tests. The results from 1.5 mm test demonstrate that degradation of cells performance immersed in IPA and in ethyl acetate mainly occurs by a decrease of Jsc and efficiency during 170 days of test. But the long-term organic liquids immersion test (180 days) without silicone sealant involved gives confidence of the reliable performance of the silicon CPV solar cells operated in liquids except for DI water. Therefore, the observed performance decay of the cells in 1.5 mm test is due to the interaction between the silicone sealant and IPA or ethyl acetate. However, long-term immersion results from 9 mm test (100 days) show that the stable electrical performance of the cell is difficult to be achieved when immersed in DI water, which is consistent with the previous report.