Longer hydrogenation duration for large area multi-crystalline silicon solar cells based on high-intensity infrared LEDs

The efficiency improvements of large area (244.34 cm2) crystalline silicon solar cells have been receiving significant attention, especially in high-efficiency multi-crystalline silicon (mc-Si) Passivated Emitter and Rear Contact (PERC) cells. The large area boron-doped mc-Si PERC cells were treated with hydrogenation for a different duration based on high-intensity infrared (HI-IR) LEDs of 940 nm. Compared to the boron-doped monocrystalline silicon (mono-Si) PERC cells, different trends of efficiency improvement were displayed after various hydrogenation duration. The results showed that the amplitude of the efficiency improvement was enhanced to the maximum around 8 min but then slowly decreased with the increasing hydrogenation duration. Moreover, we found that the iron-boron (Fe-B) pairs may occupy the dominant role in hindering the improvement of efficiency and the light-induced degradation (LID) after hydrogenation. The trend of efficiency improvement depended on the density of interstitial iron ions (Fei+) and the formation and dissociation of Fe-B pairs. Therefore, a longer duration of hydrogenation was required for mc-Si PERC cells than for mono-Si PERC cells to enhance the efficiency and suppress the degradation. Additionally, the duration of hydrogenation was significantly shortened to 1 min when the pre-LID was applied, then the appropriate extension of the hydrogenation duration was more conducive to the efficiency improvement of mc-Si PERC cells.