Back contact concentrator n/sup +/pp/sup +/ silicon solar cells

A new concept for back contact concentrator silicon solar cells is presented, called CEP cell. This structure is based on n/sup +/pp/sup +/ conventional cells. It keeps a front metallization to collect the current, that is carried to the rear side through a few number of metallized holes. Theoretical calculations of efficiency shows that this kind of grid has lower series resistance and shadowing factor than a conventional n/sup +/pp/sup +/ cell. A new method to drill holes in silicon is reported: high speed machining with diamond-coated mills of small diameter. A few number of holes have been drilled in silicon wafers and in processed solar cells. No significant reductions of solar cell efficiency has been observed before and after the hole drilling. This results suggest that material damage is small or at least compatible with good cell performance. A first series of cells for 100 suns have been produced, but have not been measured with back contact.