Recent research on light-induced degradation of crystalline Si solar cells and modules is reviewed. The first paper on the issue was published in 1973 when efficiency of solar cells using 1 Ω·cm, B-doped CZ wafers degraded under illumination. Since mid 1990’s, several studies have been performed to investigate the mechanism of the light degradation and also to provide practical solutions to annihilate the degradation. Numerous experiments have been carried out regarding the effects of impurities including B, Ga, P, O and processing parameters such as annealing temperature. Recent analysis on weathered solar modules supported the LID is in agreement with a model attributing the lifetime degradation to oxygen and boron complex. The reduction of the concentration of B and O or substitution of boron by gallium are found to suppress the degradation and to realize cell efficiency further.

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