Frequency-Dependent Variation of LeTID Degradation and Recovery Using Low Intensity with Different AC Biasing in TOPCon Solar Cells

The efficiency and reliability of photovoltaic technologies are essential for the global transition to sustainable energy systems. Tunnel oxide passive contact (TOPCon) solar cells have gained prominence due to their high conversion efficiency and improved long-term performance. Light and elevated temperature-induced degradation (LeTID) poses a significant challenge, reducing efficiency and operational stability. Research has primarily focused on understanding the underlying mechanisms of LeTID and developing mitigation strategies. The role of alternating current (AC) biasing waveforms remains underexplored, particularly under varying frequencies. We investigated the effects of sinusoidal, square, and triangular AC waveforms at frequencies of 100 kHz, 500 kHz, and 1 MHz on the performance recovery of 4 × 4 cm² TOPCon solar cells degraded under 0.5-sun illumination at 85°C for 11 h. Regeneration was conducted for 2 h using a peak-to-peak voltage (Vpp) of 1.4 V. Square and sinusoidal waveforms at 500 kHz and 1 MHz achieved the highest recovery across all key parameters. Triangular waveforms, although effective, demonstrated slightly lower recovery, particularly at lower frequencies. The findings highlight the importance of waveform characteristics and frequency in mitigating LeTID effects. Future work will optimize waveform parameters, such as amplitude and duty cycle, to maximize regeneration efficiency. Long-term field tests will validate these methods' applicability under real-world operating conditions, ensuring the durability and stability of TOPCon solar cells in large-scale deployments.