Abstract
Hydrogen passivation (H-passivation) was performed to inactivate the electrically active defects in spherical Si solar cells fabricated by the dropping method. The atomic hydrogen activated by RF plasma passivated the dangling bonds in the crystal grains, and solar cell performance was improved. The distribution of defects and the crystal quality before and after H-passivation were observed by electron-beam-induced current (EBIC) and transmission electron microscopy (TEM). The recombination sinks were observed by EBIC as dark lines of grain boundaries, wide dark areas and local dark spots in the grains. The effect of H-passivation was observed at parts of the grain boundaries and the wide dark areas, but not at the local dark spots in the grains. TEM observation showed that the crystal grains of the areas with dark spots included many dislocations and that the crystal quality at the wide dark areas is microcrystalline (<100 nm). These results indicate that the bulk region of microcrystal grains and portions of grain boundaries are inactivated effectively by H-passivation.