Study of the Hydrogen Passivation Effect of Low-Temperature-Deposited Amorphous Silicon Layers on SiGe Solar Cells Grown on a Silicon Substrate

In this study, we explored the use of low-temperature deposited a-Si:H(i) as a hydrogen source for the hydrogenation of SiGe solar cells on Si substrates. Cells integrated with a-Si:H(i) layers exhibited significant performance improvements after thermal annealing, with a maximum enhancement of 50 mV (20.2%_rel), 8%_abs (15%_rel), and 1%_abs (44%_rel) in V_OC, FF, and efficiency, respectively. These results, along with Raman spectroscopy measurements, confirm that hydrogen was released from a-Si:H(i) during thermal treatment and likely diffused into the SiGe/Si cells, providing defect passivation. External quantum efficiency measurements further revealed that the passivation enhancement occurred mainly on the front surface and nearby, indicating that hydrogen primarily diffused into the near-surface region and passivated defects in that area. The correlation between the changes in the hydrogen content from a-Si:H(i) and variations in V_OC after thermal annealing was also examined to further understand the hydrogen passivation effect. Overall, this study demonstrates the successful implementation of hydrogenation using a-Si:H(i) as a hydrogen source with significant improvements in cell performance, providing potential pathways for developing efficient SiGe/Si solar cells.