Rapid thermal processing of cost‐effective contacts for silicon solar cells

Abstract

This paper reports on the investigation of rapid thermal processing (RTP) of contacting the Al‐BSF solar cell with Ag, Cu, and Ni in conjunction with aerosol printing technique. The study showed a liftoff and delamination, respectively, for the bi and tri stack layers of Ag frit/Ni and Ag frit/Ni/Cu fired above 790°C peak firing temperature. The 770°C peak firing temperature gave excellent electrical performance for both bi and tri stack layer contacts, which is not favorable to forming thick back surface field (BSF) required for high open circuit voltage (VOC). This suggests that the bilayer and trilayer contacts involving Ag frit are limited to low peak firing temperature, but Ni frit, on the other hand, showed a wider firing temperature range. This is supported by low reverse saturation current density (J02) of 1.1 × 10−11 A/cm2 and high shunt resistance (RSH) of 5750 Ω·cm2 for the Ni frit fired at 800°C peak firing temperature. More so, the adhesion of Ni Frit to silicon is better than Ag counterpart as evidenced in the SEM micrograph. Thus, by adopting RTP Ni/Cu contacts, the cost of metallization of solar cell can be dropped from 35% of total processing cost to only 5% to 6%, which is approximately 30% drop in the total cost of processing.

Implementation of Nickel and Copper as Cost-Effective Alternative Contacts in Silicon Solar Cells

“…This occurrence could stem from multiple factors, including differential thermal expansion, interfacial reactions, and inadequate surface preparation, among others. These observations align with previous study [25], which reported similar lift-off and delamination issues in aerosol printed bi and tri stack layers of Ag frit/Ni and Ag frit/Ni/Cu when fired above 790°C peak firing temperature. The efficiency and series resistance parameters, plotted based on finger width associated with lift-off and delamination in stacked contacts, are presented in Fig.…”

Implementation of nickel and copper as cost‐effective alternative contacts in silicon solar cells

“…This occurrence could stem from multiple factors, including differential thermal expansion, interfacial reactions, and inadequate surface preparation, among others. These observations align with a previous study, 26 which reported similar lift‐off and delamination issues in aerosol printed bi‐ and tri‐stack layers of Ag frit/Ni and Ag frit/Ni/Cu when fired above 790°C peak firing temperature.…”