Monocrystalline Si solar cells are fabricated from Czochralski (Cz) Si, which contains 1017–1018 cm−3 oxygen atoms. Cz Si undergoes degradation during high-temperature thermal processing steps, such as dopant diffusion to form the p-n junction. This degradation in the bulk minority carrier lifetime can be related to the formation of oxygen precipitates. We found that a high-temperature annealing process known as tabula rasa (TR) not only mitigates process-induced degradation via oxygen precipitate nuclei dissolution, but also modifies subsequent light-induced degradation. We report on the bulk carrier lifetime of n- and p-type Cz Si after TR, which homogenizes the interstitial oxygen in the bulk Si to its monoatomic form in either an N2 or O2 environment. A control sample, which was not subjected to a TR processing step, experienced severe process-induced degradation during a boron emitter thermal budget as oxygen precipitates were formed in the Si bulk. These precipitates could be imaged using photoluminescence. Additionally, samples that underwent a TR processing step prior to the boron emitter thermal budget show efficient gettering of metallic impurities compared to the control sample, which showed a decline in the implied open-circuit voltage after the gettering step. Furthermore, modification of the interstitial oxygen bonding by TR had a strong effect on the light-induced degradation kinetics. Instead of a typically observed monotonic decrease, minority carrier lifetime increases first, followed by a nonmonotonic decrease over a ∼20 h period. We conclude that by modifying the interstitial oxygen bonding via TR pretreatment, p-type Cz Si wafers become substantially resistant to harsh solar cell processes and strongly modified light-induced degradation, which would open alternative ways to mitigate this degradation mechanism.

中文翻译：

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Tabula Rasa 对由直拉硅制造的太阳能电池的工艺和光诱导降解的影响

单晶硅太阳能电池由直拉 (Cz) Si 制成，其中包含 1017-1018 cm-3 氧原子。Cz Si 在高温热处理步骤中会发生退化，例如掺杂剂扩散以形成 pn 结。体少子寿命的这种退化可能与氧沉淀物的形成有关。我们发现，称为白板 (TR) 的高温退火过程不仅可以通过氧沉淀核溶解减轻过程诱导的降解，而且还可以改变随后的光诱导降解。我们报告了 TR 后 n 型和 p 型 Cz Si 的散装载流子寿命，这将散装 Si 中的间隙氧在 N2 或 O2 环境中均质化为其单原子形式。未进行 TR 处理步骤的对照样品，由于在 Si 体中形成氧沉淀，在硼发射体热预算期间经历了严重的工艺诱导退化。这些沉淀物可以使用光致发光成像。此外，与对照样品相比，在硼发射体热预算之前经历了 TR 处理步骤的样品显示出对金属杂质的有效吸杂，这表明吸杂步骤后隐含的开路电压下降。此外，TR 对间隙氧键的修饰对光诱导降解动力学有很强的影响。与通常观察到的单调减少不同，少数载流子寿命首先增加，然后在 20 小时内非单调减少。我们得出结论，通过 TR 预处理修改间隙氧键，