Effect of Firing Temperature on Damp Heat Stability of n-TOPCon Solar Cells’ Rear Side

Abstract

Laser-enhanced contact optimization (LECO) technology is one of the ideal candidates to reduce front contact resistance and metal-induced recombination of n-type tunnel oxide-passivated contact (n-TOPCon) solar cells. However, there are concerns regarding the reliability of TOPCon modules processed by using LECO, especially in hot and humid conditions. This study explores the degradation of the front and rear sides of TOPCon solar cells under different firing temperatures through highly accelerated temperature and humidity stress testing (HAST) and dry thermal stress testing (DST). It reveals that 700°C is the optimal firing temperature to balance efficiency and stability. The degradation was mainly induced by moisture corrosion during testing. The solar cells showed a notable reduction in PCE, with relative decreases of ∼5.89% after HAST testing. The primary cause of degradation is a considerable increase in recombination within the metallized regions, likely due to contact corrosion. The results of mini module-level tests demonstrated that rear-side moisture corrosion was the dominant factor influencing the damp-heat resistance of TOPCon solar cells. This study provides critical insights into the influence of firing temperatures on the damp-heat resistance of LECO-processed TOPCon solar cells and long-term reliability of TOPCon modules.