Gettering Efficacy of APCVD-Based Process Steps for Low-Cost PERT-Type Multicrystalline Silicon Solar Cells

Gettering of impurities plays a crucial role in production processes of multicrystalline silicon (mc-Si) solar cells. In industry this is commonly done via POCl3 diffusion gettering during emitter or back surface field formation. We report about the gettering efficacy of an alternative approach using doped glasses deposited prior to diffusion via atmospheric pressure chemical vapor deposition (APCVD). Not only effective high-temperature diffusion gettering is shown but also low-temperature internal gettering, which takes place during deposition. Both mechanisms were found to reduce interstitial iron concentrations considerably leading to significantly enhanced minority charge carrier lifetimes. Despite structure and composition of APCVD, phosphorus silicate glasses (PSG) may differ considerably from POCl
₃
PSG, its overall gettering efficacy is found to be comparable or even superior. Resulting uniform sheet resistances and doping profiles are suitable for a cost-effective industrial APCVD-based codiffusion passivated emitter, rear totally diffused solar cell production process, whose applicability is demonstrated on 156 × 156 cm
²
p-type mc-Si.