UV-Ozone Oxide for Surface Clean, Passivation, and Tunneling Contact Applications of Silicon Solar Cells

We demonstrate the versatile use of UV-ozone oxide (UVo) in surface cleaning, surface passivation, diffused junction passivation, and current tunneling applications of crystalline silicon (c-Si) solar cells. A UV-ozone generated oxide is used as a surface clean for random textured c-Si samples and the effectiveness of surface clean is determined by capping with a thin layer of aluminum oxide (AlO
_x
). Our developed UVo clean has resulted in a cleaning efficiency almost comparable to that of the benchmarked RCA clean, yielding a saturation current density of 12 fA/cm
²
. When planar and textured c-Si samples are capped by a stack of UVo and AlO
_x
, a UV-ozone growth time of no more than 3 min is found to provide an optimum surface passivation. When tested on phosphorus and boron diffused junctions (with sheet resistance,
R
_sh
of 110–120
$\Omega\!/\!{\scriptstyle\square} $
), the UVo and AlO
_x
stack resulted in a
J
₀
of 11 fA/cm
²
or lower. The high-resolution transmission electron microscope imaging revealed that UVo structure is stable upon annealing for passivation activation. Last, when applied as a tunneling contact, the UVo realizes a contact resistivity (
ρ_c
) of ∼1 mΩ-cm
²
and ∼20 mΩ-cm
²
for boron and phosphorus doped metal-insulator-semiconductor contact structures, respectively, with moderately doped diffusions.