Optically induced degradation in a-Si:H solar cells

Abstract Difference spectra of optically induced changes in the surface photo-voltage response of a-Si:H solar cells show that illumination generates two sets of near midgap states which have energy levels consistent with the two energy states for dangling bond defects in this material. Recombination of photo-generated carriers in these states leads to significant degradation of cell performance for photon energies larger than the bandgap. At low temperature (−160°C), the difference spectrum indicates that although the defect states are still present, such degradation does not occur.