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) materials deposited by rf plasma enhanced chemical vapor deposition (PECVD) process from silane-argon mixtures at different volume ratios. The performance of the solar cells fabricated by using the same materials as the intrinsic layer has been correlated with the integrated SAXS intensity of the intrinsic layer. The change in the density of states due to light soaking has been 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 the increase in the structural heterogeneities in the film. Modification of the growth kinetics due to bombardment of the metastable argon (Ar*) has been found to control the amount of nanostructural heterogeneity in the material.