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/cm
²
from an implanted lightly doped B emitter (>150 ohm/□) passivated with Al
₂
O
₃
/SiNx stack. The test cell structure with lightly B doped emitter passivated with Al
₂
O
₃
/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-cm
²
, but screen printed Ag/Al contact gave a high contact resistance of 25 mΩ-cm
²
. Therefore, a selective B emitter was used in this study, which gave ~21.0% efficiency with V
_oc
of 689 mV.