LIGHT AND TEMPERATURE EFFECT ON PIN A-SI-H DEVICE PERFORMANCE

We report experimental data on light soaking of a-Si: H solar cells as well as the role played by the temperature on the metastable light-in duced defect growth. We studied the temperature and intensity dependen ce on the photoconductivity, mu tau product and density of states at t he Fermi level (g (E(f))) and we found that the rate of defect growth on the i-layer depends on the quality of the material and on the annea ling temperature, resulting from an equilibrium between light-induced and light-annealed defects. The photoresponse of the devices is mainly ruled by its microstructure, and depends on the fraction of hydrogen bounded on internal surfaces. Results suggest a correlation between th e decrease of mu tau product for electron and the increase of the frac tion of hydrogen bonded on internal surfaces, suggesting structural ch anges during the degradation process. Data show, also, that the therma l annealing effect is worthless up to 70 degrees C because of light-in duced defect-generation being the dominant process in recombination me chanisms.