Analysis of SiOx layers for silicon heterojunction solar cells

Ultra-thin SiOx layers were inserted between amorphous and crystalline silicon to improve the passivation effect in heterojunction (HJ) solar cells. To investigate the effect of oxide films on passivation, non-destructive and surface sensitive techniques were applied to characterize the surface. X-ray photoelectron spectroscopy (XPS) results revealed the coexistence of intermediate-oxidation states in SiOx layers, where the presence of Si+ and Si2+ correlated to a degradation of the passivation. Meanwhile, the distribution of intermediate-oxidation states was correlated to the surface roughness. In addition, the enhanced passivation layers fabricated in chemical solutions were demonstrated to feature the lowest film density resulting from the presence of a cage-like bonding configuration.