A new surface passivation technique for crystalline Si solar cells: Valence-mending passivation

A valence-mended semiconductor surface is free of dangling bonds and free of surface states. Such a surface is accomplished by depositing a single atomic layer of valence-mending atoms on the surface. For the Si(100) surface, valence-mending atoms include sulfur and selenium, while fluorine, chlorine and bromine serve as valence-mending atoms for the Si(111) surface. This surface passivation technique has been demonstrated to reduce contact resistance between Si and a proper metal, and at the same time reduce surface recombination velocity. The simultaneous reduction in contact resistance and surface recombination promises significantly improved efficiency in crystalline Si solar cells. This paper reviews our progress on valence-mended Si(100) surface as pertaining to photovoltaic applications and point out ways for cost-effective integration of this technique into crystalline Si solar cells.