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