Electrical and Computer Engineering Department, University of Iowa, Iowa City, IA 52242, USA. Physics and Astronomy Department, University of Iowa, Iowa City, IA 52242, USA. Optical Science and Technology Center, University of Iowa, Iowa City, IA 52242, USA. University of Iowa Informatics Initiative, University of Iowa, Iowa City, IA 52242, USA.
Nanotechnology. 2016 Oct 14;27(41):412003. doi: 10.1088/0957-4484/27/41/412003. Epub 2016 Sep 9.
There are a range of different methods to generate a nanostructured surface on silicon (Si) but the most cost effective and optically interesting is the metal assisted wet chemical etching (MACE) (Koynov et al 2006 Appl. Phys. Lett. 88 203107). MACE of Si is a controllable, room-temperature wet-chemical technique that uses a thin layer of metal to etch the surface of Si, leaving behind various nano- and micro-scale surface features or 'black silicon'. MACE-fabricated nanowires (NWs) provide improved antireflection and light trapping functionality (Toor et al 2016 Nanoscale 8 15448-66) compared with the traditional 'iso-texturing' (Campbell and Green 1987 J. Appl. Phys. 62 243-9). The resulting lower reflection and improved light trapping can lead to higher short circuit currents in NW solar cells (Toor et al 2011 Appl. Phys. Lett. 99 103501). In addition, NW cells can have higher fill factors and voltages than traditionally processed cells, thus leading to increased solar cell efficiencies (Cabrera et al 2013 IEEE J. Photovolt. 3 102-7). MACE NW processing also has synergy with next generation Si solar cell designs, such as thin epitaxial-Si and passivated emitter rear contact (Toor et al 2016 Nanoscale 8 15448-66). While several companies have begun manufacturing black Si, and many more are researching these techniques, much of the work has not been published in traditional journals and is publicly available only through conference proceedings and patent publications, which makes learning the field challenging. There have been three specialized review articles published recently on certain aspects of MACE or black Si, but do not present a full review that would benefit the industry (Liu et al 2014 Energy Environ. Sci. 7 3223-63; Yusufoglu et al 2015 IEEE J. Photovolt. 5 320-8; Huang et al 2011 Adv. Mater. 23 285-308). In this feature article, we review the chemistry of MACE and explore how changing parameters in the wet etch process effects the resulting texture on the Si surface. Then we review efforts to increase the uniformity and reproducibility of the MACE process, which is critical for commercializing the black Si technology.
有一系列不同的方法可以在硅（Si）上生成纳米结构表面，但最具成本效益和光学趣味性的方法是金属辅助湿法刻蚀（MACE）（Koynov 等人，2006 年，应用物理快报，88 卷，203107 页）。MACE 是一种可控的、室温下的湿法化学技术，它使用一层薄薄的金属来刻蚀 Si 的表面，从而在 Si 表面留下各种纳米级和微米级的表面特征或“黑硅”。与传统的“等纹理化”（Campbell 和 Green，1987 年，应用物理杂志，62 卷，243-9 页）相比，MACE 制造的纳米线（NWs）提供了更好的抗反射和光捕获功能（Toor 等人，2016 年，纳米规模，8 卷，15448-66 页）。较低的反射率和改进的光捕获可以导致 NW 太阳能电池的短路电流增加（Toor 等人，2011 年，应用物理快报，99 卷，103501 页）。此外，NW 电池可以比传统处理的电池具有更高的填充因子和电压，从而提高太阳能电池的效率（Cabrera 等人，2013 年，IEEE 光电学报，3 卷，102-7 页）。MACE NW 处理也与下一代 Si 太阳能电池设计具有协同作用，例如薄外延-Si 和钝化发射极后接触（Toor 等人，2016 年，纳米规模，8 卷，15448-66 页）。虽然几家公司已经开始制造黑硅，并且还有更多的公司正在研究这些技术，但其中大部分工作并未在传统期刊上发表，只有通过会议论文集和专利出版物才能公开获得，这使得学习该领域具有挑战性。最近有三篇专门的评论文章发表在 MACE 或黑硅的某些方面，但没有提出全面的综述，这对该行业有利（Liu 等人，2014 年，能源与环境科学，7 卷，3223-63 页；Yusufoglu 等人，2015 年，IEEE 光电学报，5 卷，320-8 页；Huang 等人，2011 年，先进材料，23 卷，285-308 页）。在这篇专题文章中，我们回顾了 MACE 的化学，并探讨了在湿蚀刻过程中改变参数如何影响 Si 表面的纹理。然后，我们回顾了提高 MACE 工艺均匀性和重现性的努力，这对于实现黑硅技术的商业化至关重要。
