Stability enhancement of crystalline silicon solar cells through electrical bias induced recovery of LeTID

Light and elevated temperature-induced degradation (LeTID) poses a critical reliability issue in industrial crystalline silicon (c-Si) passivated emitter and rear contact (PERC) solar cells under prolonged illumination and elevated temperature conditions. This study investigates the use of DC electrical biasing as an external regeneration technique to mitigate LeTID effects. The solar cells were subjected to controlled degradation under 1-sun illumination at 75, 85, and 100 °C for 11 h to simulate accelerated, field-relevant aging conditions. A clear temperature-dependent degradation trend was observed, with the most severe losses at 100 °C. Under these conditions, the normalised short-circuit current density (Jsc), open-circuit voltage (Voc), fill factor (FF), and power conversion efficiency (PCE) decreased to 0.8933, 0.8886, 0.8851, and 0.8822, respectively. The series resistance increased significantly from 1.97 to 183 Ω·cm2, indicating increased recombination and reduced charge-transport efficiency due to defect activation. Electrical recovery was performed using forward and reverse DC biasing. Forward biasing demonstrated faster, more effective regeneration, restoring efficiency to 99.94% within 7 h, whereas reverse biasing achieved 99.64% recovery in 9 h. External quantum efficiency (EQE) measurements showed that the response at 900 nm improved from approximately 72% in the degraded state to about 89% after recovery, indicating reduced bulk recombination and improved carrier collection. These results indicate that DC electrical biasing, particularly forward biasing, is an effective method for recovering LeTID-degraded PERC solar cells. While near-complete recovery of performance parameters was achieved, minor residual losses suggest that some defect activity may remain. This approach offers a promising pathway for improving the stability and long-term performance of industrial photovoltaic devices.