Low-high heterojunction of c-Si substrate and /spl mu/c-Si:H film under rear contact for improvement of efficiency

For improvement of conversion efficiencies of single-crystalline silicon (c-Si) solar cells, the low-high heterojunction structure of p-type c-Si substrate and a highly conductive B doped hydrogenated microcrystalline silicon (c-Si:H) film with a wide optical bandgap under a rear contact has been investigated. This paper reports that a conversion efficiency of 21.1% was obtained for a 5 cm/spl times/5 cm c-Si solar cell with the /spl mu/c-Si:H film. This result has come from the examinations of the depositing conditions of the film and the improvement of rear reflection using a SiN film between the /spl mu/c-Si:H film and the rear contact. From TEM observations, it was clear that the /spl mu/c-Si:H film consisted of two kinds of domain classified by the crystallite degree of spatial order of Si atoms.