Plasma immersion ion implantation for interdigitated back passivated contact (IBPC) solar cells

We present progress to develop low-cost interdigitated back contact solar cells with pc-Si/SiO
₂
/c-Si passivated contacts formed by plasma immersion ion implantation (PIII). PIII is a lower-cost implantation technique than traditional beam-line implantation due to its simpler design, lower operating costs, and ability to run high doses (1E14-1E18 cm
^-2
) at low ion energies (20 eV-10 keV). These benefits make PIII ideal for high throughput production of patterned passivated contacts, where high-dose, low-energy implantations are made into thin (20-200 nm) a-Si layers instead of into the wafer itself. For this work symmetric passivated contact test structures grown on n-Cz wafers with PH
₃
PIII doping gave implied open circuit voltage (iV
_oc
) values of 730 mV with J
_o
values of 2 fA/cm
²
. Samples doped with B
₂
H
₆
gave iV
_oc
values of 690 mV and J
_o
values of 24 fA/cm
²
, outperforming BF
₃
doping, which gave iV
_oc
values in the 660-680 mV range. Samples were further characterized by photoluminescence and SIMS depth profiles. Initial IBPC cell results are presented.