经过半个多世纪对硅腐蚀的研究形成了一个共识：硅在碱溶液中的腐蚀通常被认为是 各向异性的且形成正金字塔结构，而硅在 HF 酸中的腐蚀通常被认为是各向同性的且形成 多孔类结构。 不管硅是在碱中腐蚀还是 HF 酸中腐蚀，在硅-硅界面处所发生的硅的氧化和 溶解过程都会涉及到电子的转移， 并导致硅表面是动态硅氢键终端的。 两种腐蚀主要的区 别是：硅在碱中腐蚀无空穴参与而在 HF 酸溶液中腐蚀是常常伴有空穴的参与， 这种空穴 的参与将导致形成二氧化硅， 然而二氧化硅的腐蚀是各向同性的，这就破坏了硅本身各个 晶面之间的本征差异， 因此掩盖了硅本身的各向异性腐蚀特性。多年来， 在 HF 酸溶液中 实现硅的各向异性腐蚀一直是研究者们的奋斗目标。 幸运的是：经过大量实验探索， 本文 不仅实现了硅在 HF 酸中类似于碱中的各向异性腐蚀形成金字塔结构，而且还在 HF 酸中 发明了多种制备陷光性能优于正金字塔结构的倒金字塔结构的方法， 最后采用这两种新型 的制绒方法制备硅太阳能电池的绒面结构并组装太阳能电池。 本文首先在 HF-铁盐和 HF-铜盐两个体系研究了溶液中不同阴离子对硅腐蚀的影响。 结果发现溶液中氯离子存在时，将会对金属离子起到络合作用改变硅的腐蚀形貌；而硫酸 根的存在不影响硅本身的腐蚀； 硝酸根的存在将会增强溶液的氧化性， 最终在不同体系中 不同金属催化作用下形成硅金字塔结构或类金字塔结构、硅纳米线结构或是多孔硅结构。 究其本质原因：形成金字塔结构或类金字塔结构是由于反应动力主要以硅的导带电子转移 为主，而形成纳米线结构或多孔结构是由于反应动力主要以硅的价带电子转移为主。 其次本文详细讨论了 HF-CuCl2-卤化物体系（尤其是 HF-CuCl2-HCl 体系）中硅的腐蚀 行为。 我们发现在该腐蚀体系中硅完全以在碱中各向异性腐蚀的方式发生并在表面形成完 美光滑的正金字塔结构， 这种现象是首次在 HF 酸中被发现的，因为以往的研究表明在 HF 酸中硅一般以各向同性的方式发生腐蚀形成典型的多孔结构。 受有机化学中金属催化 C-H 键活化或氟化的思想启发，我们提出了新型的金属催化硅各向异性腐蚀的机理。 这种腐蚀 是完全依靠于硅导带的电子为媒介实现的铜离子催化硅各向异性腐蚀，因此这种腐蚀是不 需要空穴参与的且完全类似于碱腐蚀一样的化学腐蚀过程， 这一机制也得到了电化学表征 的有力验证。 深入研究后还发现， 提高腐蚀剂中的铜离子浓度和腐蚀温度将提高硅的反应 速率，减少硅表面制绒的时间。此外， 该方法还可应用于高浓度硼掺杂 p 型硅制备金字塔 结构，结束了其以往在碱中各向异性腐蚀自停止现象， 即难以在高浓度硼掺杂 p 型硅表面 制备金字塔结构。 更有意义的是本文还发明了三种新型的基于 HF 溶液制备倒金字塔结构的方法。 其一， 硅表面周期性 PMMA 掩模板与 HF 酸各向异性腐蚀（HF-CuCl2-HCl） 结合制备倒金字塔结 构；其二， 硅表面 Si-H 键的改性与 HF 酸各向异性腐蚀（HF-CuCl2-HCl）协同制备倒金字 塔结构；其三， 硅在含空穴注入氧化剂的 HF 酸中各向同性腐蚀与 HF 酸各向异性腐蚀协 作制备倒金字塔结构。 因此， 这三种方法改变了以往只能在碱中利用光刻掩模板的作用制 备硅倒金字塔结构的单一格局， 为硅腐蚀提供了新的思路和方法。 最后，利用硅在 HF 酸中制备正金字塔结构和倒金字塔结构的方法为金刚线切硅表面 制绒并构筑太阳能电池。由于倒金字塔结构具有由于正金字塔结构的陷光性能，因此制备 电池转换效率更高， 初步实现最高转换效率为 19.18 %， 开路电压为 0.637 V， 短路电流为 9.106 A， 填充因子为 81.32 %。

Over the past half century's studies established that all alkaline solutions are anisotropic etchants which produce typical pyramidal textures on Si(100) wafers, whereas HF solutions remove silicon in an isotropic manner, resulting in the formation of porous silicon (PSi). Whether in acidic or alkaline solutions, open-circuit etching of crystalline silicon involves charge-transfer process across silicon/solution interface, i.e., oxidation of silicon and concurrent reduction of etching species, and results in dynamically hydrogen-terminated silicon surfaces. However, there is one major difference between the charge-transfer processes. Alkaline etching of silicon does not require holes, while HF etching of silicon requires hole injection from strong oxidants with enough positive electrode potentials to initiate silicon etching and the redox reactions or charge transfer can occur at spatially separated sites on silicon surface, and the redox reactions or charge transfer take place directly at the scale of individual atoms. Therefore, the anisotropic etching of crystalline silicon in HF aqueous solutions has been an elusive goal for many years. Lucily, based on large amount of experiments, we not only come true the goal that HF etching of crystalline silicon forming upright pyramid structure in an anisotropic manner identical to alkaline etching of crystalline silicon, but also we discovered three methods for fabricating inverted pyramid structure in HF solutions which has better light traping performance than upright pyramid. Finally, we choose these two facile methods to texturing silicon surface and fabricating solar cell. We firstly detailed discussed the effect of different anions on silicon etching in the two etching system: HF-Fe(III) and HF-Cu(II) solutions. It was found that the presence of chloride ions in the solution would change the corrosion morphology of the silicon by complexing the metal ions. The presence of sulfate radical ions does not affect the corrosion of silicon. The presence of nitrates radical ions will enhance the oxidability of the solution. Eventually form silicon pyramid structure or pyramid-like structure, silicon nanowire structure or porous silicon structure in different systems. The essential reasons are as follows: the formation of pyramid structure or pyramid-like structure is due to the reaction force is mainly dominated by the conduction band electron transfer of silicon, while the formation of nanowire structure or porous structure is due to the reaction force is mainly dominated by the valence band electron transfer of silicon. Secondly, the corrosion behavior of silicon in HF-CuCl2-halide systems (especially HFCuCl2-HCl system) are discussed in detail. It was found that in this etching system, the silicon completely etched in the form of anisotropic way as that etching in alkaline solutions and formed a perfectly smooth upright pyramid structure on the surface. This phenomenon was first discovered in HF acid, because previous studies generally formed a typical porous silicon structure in an isotropic manner in HF acid. Inspired by the metal catalysis C-H bond activation or fluoride in organic chemistry, we put forward that the mechanism of metal catalysis silicon anisotropic etching, silicon etching totally rely on charge transfer by conduction band of silicon so as to realize the copper ion catalytic silicon anisotropic etching, so the whole etching process does not need holes as that etching in alkaline solutions and the mechanism got strong authentication by the electrochemical characterization. Further investigation showed that increasing the concentration of copper ion in the etchant and the etching temperature would increase the reaction rate of silicon and reduce the time of texturing silicon surface. In addition, this method can also be extended to prepare the pyramid structure of p-type silicon with high concentration doped of boron, ending the previous phenomenon that it is difficult to fabricate the pyramid structure on the surface of silicon when etching in alkaline solutions. More significantly, three facile methods for preparing inverted pyramid structures in HF solution have also been developed in this paper. One is the preparation of periodic PMMA masks on silicon surfaces combined with HF acid anisotropic etching (HF-CuCl2-HCl) to prepare inverted pyramid structures. The other is synergistic combination of surface modification and anisotropic HF etching (HF-CuCl2-HCl) of silicon enables facile and scalable fabrication of inverted pyramids. Thirdly, inverted pyramid could be fabricated by introducing hole-injection oxidants into the anisotropic HF etching solutions. Therefore, these three methods have changed the single pattern of the silicon inverted pyramid structure which can only be fabricated in the alkaline solutions assisted by the mask, which provides a new idea and method for silicon etching. Finally, applying the method of preparing upright pyramid structure and inverted pyramid structure in HF solutions to texture silicon surface and fabricated solar cell. The fabricating process of solar cell had been investigated on Diamond-Wire-Sawn (DWS) monocrystalline silicon based on upright pyramid structure and inverted pyramid structure by copper ion catalysis initiated silicon anisotropic etching. Due to the better light trapping performance of the inverted pyramid structure than the upright pyramid structure, it possess a higher efficiency. A power conversion efficiency of 19.18 %, open circuit voltage of 0.637 V, short circuit current of 9.106 A and fill factor of 81.32 % were obtained.