Recent achievements in amorphous/crystalline silicon heterojunction (SHJ) solar cells and perovskite/SHJ tandem solar cells place hydrogenated amorphous silicon (a-Si:H) at the forefront of photovoltaics. Due to the extremely low effective doping efficiency of trivalent boron in amorphous tetravalent silicon, light harvesting of aforementioned devices is limited by their fill factors (FFs), a direct metric of the charge carrier transport. It is challenging but crucial to develop highly conductive doped a-Si:H with minimal FF losses. Here we report that light soaking can efficiently boost the dark conductance of boron-doped a-Si:H thin films. Light induces diffusion and hopping of weakly bound hydrogen atoms, which activates boron doping. The effect is reversible and the dark conductivity decreases over time when the solar cell is no longer illuminated. By implementing this effect to SHJ solar cells, we achieved a certified total-area power conversion efficiency of 25.18% with a FF of 85.42% on a 244.63 cm² wafer.

非晶/晶体硅异质结 (SHJ) 太阳能电池和钙钛矿/SHJ 串联太阳能电池的最新成就将氢化非晶硅 (a-Si:H) 置于光伏发电的前沿。由于三价硼在非晶四价硅中的有效掺杂效率极低，上述器件的光捕获受到其填充因子 (FF) 的限制，该填充因子是电荷载流子传输的直接指标。开发具有最小 FF 损耗的高导电掺杂 a-Si:H 具有挑战性但至关重要。在这里，我们报告了光浸泡可以有效地提高硼掺杂 a-Si:H 薄膜的暗电导率。光诱导弱结合氢原子的扩散和跳跃，从而激活硼掺杂。这种效应是可逆的，当太阳能电池不再被照亮时，暗电导率会随着时间的推移而降低。通过将此效应应用于 SHJ 太阳能电池，我们在 244.63 cm 上实现了 25.18% 的认证总面积功率转换效率和 85.42% 的 FF²晶圆。