Overview of light degradation research on crystalline silicon solar cells

Recent research on light degradation of crystalline Si materials and solar cells is reviewed. The first paper on the issue was published in 1973 when efficiency of solar cells using 1 Omega cm, B-doped CZ wafers degraded unde r illumination and recovered by annealing at a low temperature of around 20 0 degreesC. In the 1990's, several studies have been performed to investiga te the mechanism of the light degradation and also to provide practical sol utions to suppress the degradation. Numerous experiments have been carried out regarding the effects of impurities including B, Ga, P, O and processin g parameters such as oxidation temperature. To suppress the degradation, re ducing the concentration of B and O or substituting boron by gallium as dop ant was found to be effective. These findings are in agreement with a model attributing the lifetime degradation to oxygen and boron. Copyright (C) 20 00 John Wiley & Sons, Ltd.