Gallium-Doped Silicon for High-Efficiency Commercial Passivated Emitter and Rear Solar Cells
Gallium-Doped Silicon for High-Efficiency Commercial Passivated Emitter and Rear Solar Cells
复制标题
DOI：
10.1002/solr.202000754
复制
发表时间：
2021-03-01
期刊：
影响因子：
7.9
通讯作者：
Murphy, John D.
中科院分区：
文献类型：
--
作者：
Grant, Nicholas E.;Altermatt, Pietro P.;Murphy, John D.
直拉生长的掺镓硅片现已成为商用钝化发射极和后电池 (PERC) 器件的主流基板，并允许保留已建立的工艺，同时提供增强的电池稳定性。我们评估了这种直拉法生长的晶圆的载流子寿命潜力与电阻率的关系，发现在没有任何吸气或氢化处理的情况下，有效寿命可以达到毫秒范围，从而证明了相对于硼掺杂硅的一个优势。其次，在光照下（某些情况下 >3000 小时）监测掺镓 PERC 电池的稳定性，并检测异常行为。虽然一些电池是稳定的，但其他电池表现出先退化后恢复的现象，让人想起在其他硅材料中观察到的光和高温诱导退化 (LeTID)。令人惊讶的是，来自一个锭的细胞在 300 摄氏度退火时表现出类似 LeTID 的行为，但在不退火时接近稳定，但对于另一锭，观察到相反的情况。此外，通常用于减轻硼氧降解的稳定过程不会影响所研究的任何细胞。 PERC 电池的二次离子质谱分析显示，在某些情况下，无意掺入的硼浓度很高。然而，即使在没有减轻光致退化的情况下，Ga掺杂硅在光照下仍然比不稳定的B掺杂硅更稳定。
Czochralski-grown gallium-doped silicon wafers are now a mainstream substrate for commercial passivated emitter and rear cell (PERC) devices and allow retention of established processes while offering enhanced cell stability. We have assessed the carrier lifetime potential of such Czochralski-grown wafers in dependence of resistivity, finding effective lifetimes well into the millisecond region without any gettering or hydrogenation processing, thus demonstrating one advantage over boron-doped silicon. Second, the stability of gallium-doped PERC cells are monitored under illumination (>3000 h in some cases) and anomalous behavior is detected. While some cells are stable, others exhibit a degradation then recovery, reminiscent of light and elevated temperature-induced degradation (LeTID) observed in other silicon materials. Surprisingly, cells from one ingot exhibit LeTID-like behavior when annealed at 300 degrees C but near stability when not annealed, but, for another ingot, the opposite is observed. Moreover, a stabilization process typically used to mitigate boron-oxygen degradation does not influence any cells that are studied. Secondary-ion mass spectrometry of the PERC cells reveals significant concentrations of unintentionally incorporated boron in some cases. Nevertheless, even in the absence of mitigating light-induced degradation, Ga-doped silicon is still more stable than unstabilized B-doped silicon under illumination.