Direct de-ionized (DI) water immersion cooling has been verified to be an effective method of managing the operating temperature of silicon solar cells under concentration. However, the stable electrical performance is difficult to be achieved. Possible factors from bare cell self, materials for tabbing cells were investigated in this study for understanding the degradation mechanism. Long term immersion results showed that no significant degradation on bare cells operated in DI water at 65 degrees C. When cells were tabbed using lead-based solder and flux, the short circuit current (I-sc) of cells decreased with exposure time, notably under sunlight, but it was not observed for cell open circuit voltage (V-oc). The epoxy tabbed cells test also demonstrated that the tabbed cells without lead-based solder and flux involved were also found drop in I-sc but with slower rate. The presence of lead and tin black oxides on the lead based-soldered tabbed cells and red deposition on the epoxy tabbed cells confirmed the occurrence of galvanic corrosion. However, particular cleaning recovers the I-V towards its initial values for the former tabbed cells, and partial recovery for the latter tabbed cells, which indicates that the cells are not damaged after long-time DI water immersion. (C) 2011 Elsevier Ltd. All rights reserved.