Record efficiency of 16.7% in EFG ribbon silicon

Recently obtained results of a process monitoring based on spatially resolved lifetime measurements revealed that bulk lifetime values above 300 /spl mu/s can be reached within edge-defined film-fed growth (EFG) silicon ribbons with the help of gettering and hydrogen passivation steps. Therefore, recombination losses at the wafer backside have to be considered in this material with low as grown lifetimes. The solar cell processing sequence has been adapted to the needs of this material. Besides phosphorous gettering and remote hydrogen plasma passivation a screen printed back surface field has been implemented instead of an evaporated and subsequently alloyed thin Al BSF used for Al gettering. This allows to make use of low energy photons in regions with very high bulk lifetimes. In this way an independently confirmed solar cell efficiency of 16.7% has been obtained which is the highest value that has been reported so far.