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 (J0e) 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 Voc 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 Voc of 689 mV.