Enhancing LeTID mitigation and regeneration in High-Efficiency PERC, TOPCon, and HIT crystalline silicon solar cells through Frequency-Dependent AC biasing waveform optimization

LeTID significantly impacts the performance of c-Si solar cells, particularly in PERC, TOPCon, and HIT technologies. This study investigates these solar cells’ degradation and subsequent regeneration under 1-sun illumination at 85 °C for 11 h, followed by 2-hour AC biasing at 500 kHz using sinusoidal, square, and triangular waveforms. The degradation results indicate that PERC cells exhibit the highest performance loss, with J_sc, V_oc, FF, and η declining by approximately 4.56 %, 5.03 %, 4.15 %, and 4.18 %. TOPCon cells moderate degradation with reductions of 3.33 %, 4.56 %, 3.98 %, and 3.92 %, while HIT cells exhibit the least degradation, with losses of only 1.84 %, 1.76 %, 1.74 %, and 1.64 %. Regeneration analysis reveals that square waveform AC biasing is the most effective, restoring 99.73 % of efficiency in TOPCon, 99.54 % in HIT, and 96.78 % in PERC. The superior performance of square waveform AC biasing is attributed to its sharp voltage transitions, which enhance charge carrier redistribution and defect passivation. Sinusoidal waveforms demonstrate moderate recovery, while triangular waveforms are the least effective. The findings establish TOPCon as the most responsive technology to AC biasing-based LeTID mitigation, while PERC remains the most vulnerable due to passivation instability and recombination losses. These results highlight square waveform AC biasing as a promising technique for improving the stability and efficiency of c-Si solar cells in long-term field operations.