Optimizing Emitter Diffusion Process for Atmospheric Pressure Dry Nanotextured Monocrystalline PERC

In this article, we present an optimization of the emitter diffusion for nanotextured p -type monocrystalline silicon solar cells using atmospheric pressure dry etching (ADE) in conjunction with a post-ADE short acidic etch in a passivated emitter and rear cell (PERC) architecture. The optimization of the phosphorus oxychloride diffusion process was realized by first investigating the emitter sheet resistance and emitter recombination current density to achieve improved electrical properties and cell performances at a later stage. The optimization of the diffusion process enables an excellent homogeneity for emitter sheet resistance of 105 O/sq with minimized standard deviation of 3%, a decreased emitter saturation current density of ∼120 fA/cm 2 , a peak doping concentration of 2.2 × 10 20 cm −3 and depth of the highly doped surface region of 20 nm, still in the range that is required for good contact formation. By step optimization of the emitter formation of ADE textured PERC solar cells, an efficiency improvement of 0.6% abs could be reached leading to best conversion efficiency of 20.9%.