Silicon solar cell emitters: optimization and comparison of two different technologies

Considering recent modifications on n-type highly doped silicon parameters, a new emitter optimization was made based on one-dimensional models with analytical solutions. In order to obtain good accuracy, a fifth order approximation has been considered. Two kinds of emitters, homogeneous and locally deep diffused (LDD), with Gaussian profile of n/sup +/pp/sup +/ solar cells were optimized. According to the authors' results: homogeneous emitter solar cells show their maximum efficiencies (/spl eta//spl cong/ 21.60-21.74%) with doping levels N/sub s/=1/spl times/10/sup 19/-5/spl times/10/sup 18/ (cm/sup -3/) and (1.2-2.0) /spl mu/m emitter thickness range. LDD emitter solar cells provide a slightly higher efficiency (/spl eta/=21.82-21.92%), with N/sub s/=1/spl times/10/sup 20/ (cm/sup -3/) With 2.0 /spl mu/m thickness under metal-contacted surface and N/sub s/=1/spl times/10/sup 19/-5/spl times/10/sup 18/ (cm/sup -3/) with (1.2-2.0) /spl mu/m thickness range, (sheet resistance range 90-100 /spl Omega/) under passivated surface. Although LDD emitter solar cells have a higher efficiency than homogeneous emitter ones, the required technology is more complex and their overall interest for practical applications is questionable.