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 ⁺pp⁺ solar cells were optimized. According to the authors´ results: homogeneous emitter solar cells show their maximum efficiencies (η≅ 21.60-21.74%) with doping levels N_s=1×10¹⁹-5×10¹⁸ (cm^-3 ) and (1.2-2.0) μm emitter thickness range. LDD emitter solar cells provide a slightly higher efficiency (η=21.82-21.92%), with N _s=1×10²⁰ (cm^-3) With 2.0 μm thickness under metal-contacted surface and N_s=1×10¹⁹-5×10¹⁸ (cm^-3 ) with (1.2-2.0) μm thickness range, (sheet resistance range 90-100 Ω) 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