Thermal stability of laser-assisted fired TOPCon solar cells: Crucial insights for module manufacturing, certification testing, and field conditions

Laser-assisted firing (LAF) technology, such as laser-enhanced contact optimization (LECO), is increasingly utilized in the mass production of tunnel oxide passivated contact (TOPCon) solar cells. However, concerns regarding the thermal stability of LAF TOPCon remain. This study systematically evaluates the thermal stability of LAF TOPCon cells at both the moderate temperatures encountered during module fabrication and a higher temperature of 450 °C. While soldering did not have a negative impact on cell performance, lamination resulted in a ∼0.29 % absolute power conversion efficiency ( PCE ) loss, primarily due to a reduction in fill factor ( FF ). The degradation is driven mainly by an increase in J 02 -like recombination, likely in the space charge region. A 1-min one-sun light soaking at room temperature effectively restores cell performance, suggesting that field operation effectively mitigates such degradation. Under repeated 450 °C rapid thermal annealing and LAF cycles, initial FF and PCE losses (∼21.6 % and ∼6.7 % absolute, respectively) are attributed to contact deterioration, but performance is restored through subsequent LAF treatment. Based on these findings, a three-state defect model and contact degradation mechanisms are proposed. These findings provide new insights into the reliability of LAF TOPCon cells and highlight key considerations for industrial processing and module reliability testing. • ∼0.29% PCE loss after the lamination process, primarily caused by FF degradation and increased J 02 -like recombination. • Rapid recovery through 1-min one-sun light soaking at room temperature, suggesting self-healing during operation. • FF degradation after high-temperature RTA, due to contact instability, which can be restored through the LAF process. • The proposal of a three-state defect model explaining the activation and recovery dynamics of thermally induced defects. • Discussions of hydrogen-related defects, and possible contributions from metal impurities and interfacial changes.