p-Type SiOx Front Emitters for Si Heterojunction Solar Cells.

We have applied p-type nanocrystalline silicon-oxide (p-SiOx) as front emitter in silicon heterojunction solar cells. The evolution of structural, optical, and electrical properties of p-SiOx as a function of the carbon-dioxide/silane flow rate ratio used in the gas mixture has been investigated, comparing also the film characteristics with those of p-type amorphous and nanocrystalline silicon thin films often used in the cells. Selected p-SiOx films with suitable electrical properties have been inserted in silicon heterojunction solar cells based on n-type FZ c-Si <100> wafers, passivated with ultrathin intrinsic a-Si:H buffers. Improvement of all the photovoltaic parameters has been observed with the emitter with higher oxygen content. The results have been correlated with the increased transparency and enhanced field-effect passivation obtained thanks to the presence of sufficient carbon dioxide in the gas mixture for the p-SiOx layer growth. [ABSTRACT FROM AUTHOR]