Correlation of nanostructural heterogeneity and light induced degradation in a-Si : H solar cells

The small angle X-ray scattering (SAXS) method was adopted to estimate the nanostructural heterogeneity in hydrogenated amorphous silicon (a-Si:H) mat erials deposited by rf plasma enhanced chemical vapor deposition (PECVD) pr ocess from silane-argon mixtures at different volume ratios. The performanc e of the solar cells fabricated by using the same materials as the intrinsi c layer has been correlated with the integrated SAXS intensity of the intri nsic layer. The change in the density of states due to light soaking has be en measured in solar cell structure by a dual beam photoconductivity method . We have observed a systematic increase in the photoinduced degradation of the photoconductivity, defect density and the solar cell parameters with t he increase in the structural heterogeneities in the film. Modification of the growth kinetics due to bombardment of the metastable argon (Ar*) has be en found to control the amount of nanostructural heterogeneity in the mater ial.