Enhancing regeneration and long-term reliability of c-Si (HIT) solar cells through AC power application for light- and elevated temperature-induced degradation mitigation

Crystalline silicon solar cells are highly efficient, but their long-term stability is compromised by Light and Elevated Temperature Induced Degradation (LeTID), which occurs under moderate illumination and elevated temperatures. While much research has focused on LeTID in multi-crystalline and monocrystalline silicon cells, with mitigation techniques like thermal treatments and optimized passivation, the use of alternating current (AC) biasing waveforms for LeTID mitigation and performance recovery has not been thoroughly explored. This study investigates the regeneration of a heterojunction with intrinsic thin-layer (HIT) solar cells (4 × 4 cm²), subjected to LeTID conditions (1 sun illumination at 75 °C for 11 h), using sinusoidal, square, and triangular AC waveforms at frequencies of 100 kHz, 500 kHz, and 1 MHz. LeTID exposure significantly reduced efficiency, open-circuit voltage (V_oc), short-circuit current (J_sc), and fill factor (FF). After applying AC waveforms, substantial recovery was observed across all performance metrics, with square waveforms at 1 MHz providing the most significant recovery, restoring V_oc, J_sc, FF, and efficiency to 99.99% of their initial values. Sinusoidal waveforms showed effective recovery, reaching 99%-99.5%, while triangular waveforms exhibited somewhat lower recovery, in the range of 97%-99%. These findings highlight the importance of waveform shape and frequency in facilitating hydrogen redistribution and defect passivation. The results suggest that high-frequency AC biasing techniques could be integrated into industrial processes to enhance the long-term stability and reliability of HIT solar cells, supporting the broader deployment of high-efficiency photovoltaic systems.