Impact of carrier injection level on light-induced degradation of Cz-Si solar cell performance
Light-induced performance degradation, which has been significant for highly efficient Cz-Si solar cells, was investigated for fundamental interpretation of the phenomenon. Illuminations with light intensities of 0.2 to 100 mW/cm2 were carried out on two Cz-Si solar cells fabricated from different base resistivity substrate. Cell performances decayed double exponentially with several types of degradation processes indicating a very initial fast drop. Decay curve fittings with simple exponential equations obtained time constants, and the correlation with illumination intensity was evaluated. The resultant decay times were almost independent of illumination intensity over 1 to 100 mW/cm2. The trend of the independence appeared more significantly on a cell with higher base resistivity. Defect concentration much less than injected carriers were considered for the physical image of the decay time saturation.