Factors affecting the performance of thin dendritic Web silicon front surface field (n/sup +/np/sup +/) solar cells

A method for assessing surface passivation, based on a measurement of V/sub oc/, is presented which is sensitive to SRV from 10 to 100,000 cm/s. V/sub oc/ for a back p-n junction cell is strongly dependent on carrier recombination at the front surface. By employing such a cell structure without a FSF diffused layer, this sensitivity of V/sub oc/ to front surface conditions is amplified. From a SiN/sub x//np/sup +//Al structure, an SRV of 2,000 cm/s was inferred for the lightly-doped (20 /spl Omega/-cm) n-type dendritic Web silicon surface passivated with a low frequency direct PECVD SiN/sub x/ layer. V/sub oc/ measurements were then used to optimize the n/sup +/ process in such a FSF cell to 75 /spl Omega///spl square/ via etchback, with consideration given to properly removing residue from the screen-printed phosphorus paste in order to present a clean n/sup +/ surface for SiN/sub x/ deposition and to assessing the impact of applying high SRV metal contacts to the front n/sup +/ surface. With this optimization, production-worthy thin dendritic Web silicon PhosTop cells having low-resistance contacts and an average efficiency tightly grouped around 14.4% were obtained.