高纯冶金级硅中氢状态对缺陷、杂质钝化的行为及控制机理研究

Hydrogen passivation is able to significantly increase the electronic quality of silicon material, therefore creating a possibility to fabricate high efficiency silicon solar cells on low quality silicon wafers. Hydrogen can exist in three charge states: H+，H-和H0, which have significant distinction in mobility and reactivity. It is reported that hydrogen is not very mobile and not very reactive if it's in the wrong charge state. Never-the-less, hydrogen in right charge state can have mobility and reactivity four orders of that for hydrogen in the wrong charge state. ..By understanding the importance of the charged state of those hydrogen atoms, and working out how to control that state, we can increase - by up to a million times - how well we can move the hydrogen atoms around, and enabling the hydrogen to bond effectively to these defected regions to fix the defects. We can passivate or heal most of the crystallographic defects, and also the recombination that comes from unwanted impurities.To control the charge state, it’s a matter of giving the hydrogen the right number of electrons. We shine lasers of the right wavelength onto the silicon material; using the photons of laser of these specific wavelengths to strip the electrons off the silicon atoms; giving them to the hydrogen atoms, to put them in the charge state we want them to be in.. It is expected that laser enhanced hydrogen passivation can increase the efficiency of low cost silicon cell from 14% to 19% with a very low cost, therefore dramatically reducing the cost of electricity generated by low cost silicon solar cell for up to 20%. These research outcomes have been published in more than 10 SCI papers. ..In this research project, we would build a model to simulate the kinetic processes of hydrogen passivation and hydrogen charge state transfer. It is expected that we could find out the mechanisms of hydrogen charge state control and figure out the way to achieve more advanced hydrogenation. We will also, in theory, explain the chemical and kinetic processes of hydrogen bonding with defects.

氢钝化可以显著提高硅材料的电学性质，因此为制造低价格高效率的太阳能电池提供有效的方法。氢在硅材料中存在三种状态：H+，H-和H0。我们现有的研究结果表明，通过控制氢的状态，可以使其的迁移能力和电活性大幅提高，并使其与缺陷、杂质有效结合，最终导致氢的钝化效果提高几个数量级。前期研究结果已在SCI核心期刊上发表10余篇文章。..本研究项目将在我们前期研究的基础上，从实验上进一步探索不同状态氢（H+，H-和H0）与各种不同缺陷、杂质结合的化学反应和动力学过程，并从理论上研究不同状态氢转换和浓度控制的机理。本研究项目计划使用特定波长的激光控制氢的状态（H+，H-和H0）和浓度分布，从而大幅地提高氢的迁移性和电活性。在实验的基础上，本研究项目将模拟氢钝化的过程，从理论上解释不同状态氢钝化缺陷、杂质的动力学过程和反应过程，并解释其高效钝化效果的原理。

本项目是研究高纯冶金级硅中氢状态对缺陷、杂质钝化的行为及控制机理。项目的背景是氢钝化被发现可以显著钝化硅材料中的各种缺陷，例如位错，晶界，金属杂质和硼氧复合体等，从而大幅提升硅太阳能电池的效率。但是传统的氢钝化技术面临着一些问题，例如：1. 对于位错等结构缺陷，钝化效率偏低；2. 同一的处理方法不能同时满足多种不同缺陷的最佳钝化条件；3. 与硅太阳能电池制造工艺的兼容性较差。为了克服上述缺点，我们对氢在硅材料中的行为和钝化缺陷的机理进行了系统研究，解决了一些关键的科学问题。.. 本项目主要研究了如下科学问题：1.氢在烧结的冷却过程中的行为特征和控制机理；2.电场对氢在硅中扩散行为的影响；3.氢高效钝化硅表面态的方法和机理；4.氢高效钝化位错的方法和机理。这些研究发现了一些重要结果，简介如下：1. 在烧结的冷却过程中增加适当的光照，可以降低氢的带电状态变化，从而减少氢-缺陷复合体的分解。2. 正电场可以加速氢正离子在硅中的扩散，而抑制氢负离子在硅中的扩散，反之亦然。3. 硅的表面态是一系列准连续的缺陷态，在费米能级之上，缺陷态带正电，反之带负电。因此我们利用光照来改变氢的带电状态分布，实现氢对硅表面态更好的钝化效果。4. 研究发现氢的中性状态最有利于钝化位错，而激光调控可以改变氢带电状态，实现高效的位错钝化。.. 这些研究结果具有较大的科学意义和应用价值：1.冷却过程中氢的调控机理解释了传统氢钝化低效率的原因，并且为工业上实现高效氢钝化提供了基础。目前该技术已经授权一项国家发明专利，并且和上市公司开展了产学研合作，将该技术应用于生产线上。2.电场对氢扩散影响的研究进一步加强了控制氢行为的可能性。3.利用激光来改变氢的带电状态，实现对特定缺陷（如位错和硅表面态）的高效钝化，这属于原创性成果而且有较大的应用价值。.. 总的来说，本项目的研究解决了一些科学问题（发表相关SCI论文5篇），为更好地理解氢钝化行为和机理做出了一些贡献。