Effect of illumination conditions on Czochralski-grown silicon solar cell degradation

Abstract

The substitutional B-interstitial O-related defects induced under an illumination, specific to B-doped Czochralski-grown silicon (Cz-Si), results in a solar cell efficiency loss of up to 3%. For a fundamental interpretation, the relationship between the solar cell performance and the minority-carrier lifetime degradation, and influence of the illumination conditions were investigated. A simulation of the cell performance degradation clearly represented that the degradation was explained as a result of the carrier diffusion length degradation. From a spectroscopic illumination investigation, the degradation was found to be independent of the stress-light wavelength. A blue light illumination on a solar cell resulted in the red response degradation, suggesting that the injected carriers activated the defect in the bulk. However, the correlation between carrier injection level and the cell performance decay time was nonlinear. The observed decay times were almost independent of the illumination intensity in the range of 1 to 100 mW/cm2. This trend appeared more significantly on cells with a higher base resistivity. From the experimental results, the role of excess carriers in the defect activation was discussed.