Optoelectronic properties of ultrathin ALD silicon nitride and its potential as a hole-selective nanolayer for high efficiency solar cells
Optoelectronic properties of ultrathin ALD silicon nitride and its potential as a hole-selective nanolayer for high efficiency solar cells
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DOI：
10.1063/5.0023336
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发表时间：
2020-11
期刊：
影响因子：
6.1
通讯作者：
E. Khorani;S. McNab;Tudor E. Scheul;Tasmiat Rahman;R. S. Bonilla;S. Boden;P. Wilshaw
中科院分区：
文献类型：
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作者：
E. Khorani;S. McNab;Tudor E. Scheul;Tasmiat Rahman;R. S. Bonilla;S. Boden;P. Wilshaw
充分利用硅太阳能电池的功率转换效率限制需要使用钝化接触，使金属/硅界面处的电损耗最小化。有效的空穴选择性钝化接触仍然是该技术在工业上部署的关键挑战之一，并为串联配置的采用铺平了道路。在这里，我们报告的第一个帐户的氮化硅（SiNx）纳米层的电子性能适合有效的空穴选择性接触。我们使用X射线光电子能谱方法来研究通过原子层沉积生长的超薄SiNx，我们发现在SiNx/Si界面处确定的能带对准有利于空穴传输。在SiNx/Si界面处，薄膜的带偏移比ΔEC/ΔEV为1.62 ± 0.24。这相当于对于3 nm的膜厚度，空穴对电子的隧穿选择性增加500倍。然而，在洁净室条件下，这种膜的厚度在48 h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，这种膜的生长与氧化有关，而且，它将ΔEC/ΔEV比率改变为1.22 ± 0.18。SiNx/Si界面能带对准使SiNx纳米层成为一种有前途的架构，可以实现高效硅太阳能电池广泛寻求的空穴选择性钝化接触。
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.