Photo-induced hydrogenation and rapid cooling measure on dislocation clusters of multi-crystalline silicon PERC solar cells

The dislocations are the deep level defects with a negative impact on the multi-crystalline silicon (mc-Si) solar cells. Though potential mechanisms of dislocation formation on the silicon ingot have been studied, few investigations consider the effect of LED hydrogenation on dislocation clusters. In this study, we have explored the influence of hydrogenation on the dislocation clusters of large-area (244.34 ± 0.05 cm2) mc-Si solar cells using the high-intensity infrared LED source. However, applying normal cooling measure to hydrogenation will trigger the instability of the hydrogenation improvement effect due to residual thermal stress, so we proposed an appropriate rapid cooling measure (RCM) followed by hydrogenation and achieved optimized results. The results indicated that electrical properties, minority carrier lifetime, current density, power density and external quantum efficiency were enhanced through LED hydrogenation and RCM, and the degradation of mc-Si solar cells also was significantly suppressed. To estimate the content of dislocations after LED hydrogenation and RCM, we applied the X-ray diffraction techniques to calculate the dislocation density using the full-width at half maximum of the rocking curve at (111), (220), (311), (400) and (331) reflections. The dislocation density of mc-Si PERC solar cells was decreased by 0.12 × 108 cm−2 (±0.02 × 108 cm−2) after LED hydrogenation and RCM. Meanwhile, photoluminescence images also illustrated that LED hydrogenation passivated dislocation clusters as well as impurities and defects gathered by dislocations. Therefore, LED hydrogenation of dislocation clusters is an effective measure to improve the performance of dislocation-containing mc-Si solar cells.