We demonstrate thermally stable polysilicon (poly-Si)-based tunnel junctions (TJs), that is, n⁺-poly-Si/p⁺-poly-Si/SiO_x and n⁺-poly-Si/SiO_x/p⁺-poly-Si/SiO_x, for passivating a silicon wafer, selectively extracting holes, and being compatible with the high-temperature firing process of screen-printed metal contacts. An additional interfacial oxide between the n⁺-poly-Si and p⁺-poly-Si layers enhances thermal stability and acts as a barrier layer to mitigate dopant interdiffusion between the adjacent poly-Si layers, without significantly increasing the contact resistance. The TJ's thermal stability is investigated by analysing the TJ recombination current density J₀ and effective contact resistance ρ_c after high-temperature firing (740°C to 840°C) of nonmetallised samples. We evaluate two different TJ applications via efficiency potential calculations: (1) When the TJ is applied on the front side of a passivated-contact Si bottom cell for 2-terminal tandem cells, a calculated add-on efficiency of 9.9% for the Si bottom-cell can be achieved with the inclusion of the interfacial oxide; (2) to enable conventional metal screen-printing on a p⁺-poly-Si layer, the TJ is applied on the rear side of a single-junction Si solar cell, giving a calculated cell efficiency potential of 23.6% at 1-Sun condition. For such a configuration, in the absence of an interfacial oxide between the adjacent poly-Si layers, the cell efficiency potential improves with peak firing temperature. In summary, we successfully develop thermally stable hole-extracting TJs for the two aforementioned applications that are fully compatible with existing industrial silicon solar cell fabrication processes.

中文翻译：

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热稳定的多晶硅隧道结使下一代高效硅太阳能电池成为可能

我们展示了基于热稳定多晶硅 (poly-Si) 的隧道结 (TJ)，即n ⁺ -poly-Si/ p ⁺ -poly-Si/SiO _x和n ⁺ -poly-Si/SiO _x / p ⁺ -poly-Si/SiO _x，用于钝化硅片，选择性提取空穴，并与丝网印刷金属触点的高温烧制工艺兼容。n ⁺ -poly-Si 和p ⁺之间的附加界面氧化物-poly-Si 层增强了热稳定性并充当阻挡层以减轻相邻 poly-Si 层之间的掺杂剂相互扩散，而不会显着增加接触电阻。通过分析非金属化样品在高温烧制（740°C 至 840°C）后的 TJ 复合电流密度 J ₀和有效接触电阻 ρ _c来研究 TJ 的热稳定性。我们通过效率潜力计算评估两种不同的 TJ 应用：(1) 当 TJ 应用于 2 端子串联电池的钝化接触 Si 底部电池的正面时，Si 的计算附加效率为 9.9%可以通过包含界面氧化物来实现底部电池；(2) 在p上启用传统的金属丝网印刷⁺ -poly-Si 层，TJ 应用于单结 Si 太阳能电池的背面，在 1-Sun 条件下计算出的电池效率潜力为 23.6%。对于这样的配置，在相邻多晶硅层之间不存在界面氧化物的情况下，电池效率潜力随着峰值烧制温度而提高。总之，我们成功地为上述两个应用开发了热稳定的空穴提取 TJ，这些应用与现有的工业硅太阳能电池制造工艺完全兼容。