High Implied Voc (>715 mV) and low emitter saturation current density (?10fA/cm2) from a lightly B doped implanted emitter

In this paper, we demonstrate a very low emitter saturation current density (J_0e) of ~10 fA/cm² from an implanted lightly doped B emitter (>150 ohm/□) passivated with Al₂O₃/SiNx stack. The test cell structure with lightly B doped emitter passivated with Al₂O₃/SiNx on front and tunnel oxide/n+ poly silicon passivated back gave a high implied V_oc of 715~722 mV on ~5 Ω-cm n-type Cz wafers. It is also shown that Ti/Pd/Ag contact resistance on the lightly doped B emitter was ~2 mΩ-cm², but screen printed Ag/Al contact gave a high contact resistance of 25 mΩ-cm². Therefore, a selective B emitter was used in this study, which gave ~21.0% efficiency with V_oc of 689 mV.