Fully exploiting the power conversion efficiency limit of silicon solar cells requires the use of passivating contacts that minimize electrical losses at metal/silicon interfaces. An efficient hole-selective passivating contact remains one of the key challenges for this technology to be deployed industrially and to pave the way for adoption in tandem configurations. Here, we report the first account of silicon nitride (SiNx) nanolayers with electronic properties suitable for effective hole-selective contacts. We use x-ray photoemission methods to investigate ultra-thin SiNx grown via atomic layer deposition, and we find that the band alignment determined at the SiNx/Si interface favors hole transport. A band offset ratio, ΔEC/ΔEV, of 1.62 ± 0.24 is found at the SiNx/Si interface for the as-grown films. This equates to a 500-fold increase in tunneling selectivity for holes over electrons, for a film thickness of 3 nm. However, the thickness of such films increases by 2 A–5 A within 48 h in cleanroom conditions, which leads to a reduction in hole-selectivity. X-ray photoelectron spectroscopy depth profiling has shown this film growth to be linked to oxidation, and furthermore, it alters the ΔEC/ΔEV ratio to 1.22 ± 0.18. The SiNx/Si interface band alignment makes SiNx nanolayers a promising architecture to achieve widely sought hole-selective passivating contacts for high efficiency silicon solar cells.

中文翻译：

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超薄ALD氮化硅的光电特性及其作为高效太阳能电池空穴选择性纳米层的潜力

充分利用硅太阳能电池的功率转换效率极限需要使用钝化触点，以最大限度地减少金属/硅界面处的电损耗。高效的空穴选择性钝化接触仍然是该技术在工业上部署并为串联配置采用铺平道路的主要挑战之一。在这里，我们报告了具有适用于有效空穴选择性接触的电子特性的氮化硅 (SiNx) 纳米层的第一个帐户。我们使用 X 射线光电发射方法研究通过原子层沉积生长的超薄 SiNx，我们发现在 SiNx/Si 界面处确定的能带排列有利于空穴传输。在生长薄膜的 SiNx/Si 界面处发现带偏移比 ΔEC/ΔEV 为 1.62 ± 0.24。这相当于对于 3 nm 的薄膜厚度，空穴对电子的隧道选择性增加了 500 倍。然而，在洁净室条件下，此类薄膜的厚度在 48 小时内增加了 2 A–5 A，这导致空穴选择性降低。X 射线光电子能谱深度分析表明，这种薄膜生长与氧化有关，此外，它还将 ΔEC/ΔEV 比改变为 1.22 ± 0.18。SiNx/Si 界面能带排列使 SiNx 纳米层成为一种很有前途的结构，可以实现高效硅太阳能电池的广泛寻求的空穴选择性钝化接触。X 射线光电子能谱深度分析表明，这种薄膜生长与氧化有关，此外，它还将 ΔEC/ΔEV 比改变为 1.22 ± 0.18。SiNx/Si 界面能带排列使 SiNx 纳米层成为一种很有前途的结构，可以实现高效硅太阳能电池的广泛寻求的空穴选择性钝化接触。X 射线光电子能谱深度分析表明，这种薄膜生长与氧化有关，此外，它还将 ΔEC/ΔEV 比改变为 1.22 ± 0.18。SiNx/Si 界面能带排列使 SiNx 纳米层成为一种很有前途的结构，可以实现高效硅太阳能电池的广泛寻求的空穴选择性钝化接触。