Fig. 7 The efficiency and series resistance for different
contacts with different finger width. Highlighting on the data point
shows if the contact has a lift off or delamination, green highlight
means lift off from substrate and pink means interlayer delamination.
One of the key determinants of the viability and scalability of the
proposed alternative metallization technique is its cost-effectiveness
and potential impact on the Levelized Cost of Electricity (LCOE). Prior
research by Zhang [26] demonstrated that in traditional solar cell
manufacturing, Ag consumption is around 13-20 milligrams per watt-peak
(mg/Wp). This represents a significant cost due to the high market price
of Ag, thereby posing a potential barrier to terawatt-scale production.
In order to calculate the reduction in silver usage achieved through the
employment of a bi-layer structure, using Ag as a seed layer and either
Ni or Cu as bulk metal, all cells were weighed before printing and after
co-firing the contacts, ensuring the complete removal of solvents and
binders. The metallization patterns for each contact type were
maintained consistent with 110 fingers and 5 busbars. The cells weighed
for metal consumption analysis were carefully selected based on the
average finger width, to minimize discrepancies between samples. The
bi-layer contacts for consumption analysis underwent a two-step firing
process: once after Ag printing, and once after Ni or Cu printing. This
allowed for accurate determination of Ni and Cu consumption. As Table IV
illustrates, the average values of Ag, Ni, and Cu consumption for the
completed cells demonstrate that Ag consumption for bi-layer contacts is
below 2.5mg/Wp. This represents nearly a sevenfold reduction when
compared to the Ag contacted reference cell. Considering the Ag price of
$808, Ni price of $24 and Cu price of $8, the metallization cost per
wafer drops 80.75% lower for Ag/Ni contacts and 82.15% for Ag/Cu
contacts. The reflection of this cost drop on the LCOE is calculated
according to Lazard’s calculation [27] with System Advisor Model
(SAM) by NREL in a scenario in which it is assumed that M2 sized solar
cells are used for 1GW solar farm in south Turkiye where the solar
insolation is 5.1kWh/m2/day. The results show that for
the reference Ag contacted solar cells yields an LCOE of 8.9¢/kWh. To
analyze the effect of the bi-layer contacted cells on the LCOE, the
sensitivity analysis is carried out in which the inputs are varied
according to their electrical output parameters and metal consumption
given in Table II and Table IV, respectively. Fig. 8 shows the
sensitivity analysis results where negative correlation (to the left
from the centerline) means lower LCOE and positive correlation (to the
right from the centerline) results in higher LCOE. It is illustrated in
Fig. 7 that although the loss in power conversion efficiency due to high
series resistance has an impact to increase the LCOE around 0.35¢/kWh,
the cost drop of metal consumptions has a higher impact to lower the
LCOE of around 0.65¢/kWh. The increase in thermal budget for the contact
firing of bi-layer contacts has a limited effect on the LCOE. Therefore,
the financial implications of adopting this bi-layer metallization
approach are significant. The drastically reduced silver consumption
leads to substantial cost savings, which are directly reflected in the
LCOE.
Table IV Ag Ni and Cu consumption of the finished cells after
contact co-firing