多场耦合脉冲放电制备硅纳米颗粒及其在局域硼背场高效晶硅太阳能电池中的应用基础研究

Currently, the average conversion efficiency of Si crystalline solar cells manufactured in mass production with low cost has approached the bottleneck of less than 20%. In this project, we propose a new method to produce Si nanoparticles (NPs) from heavily boron doped monocrystalline Si ingot by using pulsed electrical discharge under coupled multi-field, and to form boron local back surface fields (BSF) with nano Si paste instead of liquid or gas source of boron regarding current complicated processes and thermal damage of boron diffusion. Molecular dynamics(MD) will be introduced to simulate the formation of Si NPs, and to reveal the mechanism for mass production of Si NPs with controllable size and size distribution using pulsed electrical discharge under coupled multi-field. Primary study of the key techniques, for instance, pulsed electrical discharge generator for semiconductor materials, customized working fluid techniques and optimization of processing parameters will be initiated. An shock wave disperse method based on megahertz ultrasound technique, and polymeric micelles templating based on the theory of steric effect will be developed to prepare long lasting and stable Si NPs paste. The mechanism for forming boron local BSF via the Si NPs paste techneque will be explored to realize good rear surface passivation with low recombination. Design of BSF patterns and sintering process will be optimized to decrease the rear metal contact area, reduce the size and number of interfacial defects, and improve performance of spectral response. Further, low cost "standardized" process flows for boron local BSF will be developed and realized. The uses of these processes/methods with proprietary intellectual property rights will largely decrease manufacturing costs, and can be one of cost-effective approaches for new generation of Si solar cells. For advancing competitiveness of China's PV products in the international market, especially for low-cost high-efficiency solar cells, the thorough research has the important theoretical significance and engineering application prospects.

针对效率20%以上晶硅太阳能电池的低成本制造技术瓶颈，提出一种以重掺硼单晶硅为原料、多场耦合脉冲放电制备硅纳米颗粒的新方法，替代液（或气态）硼源制作无高温热损伤、工艺成本低的局域硼背场。采用分子动力学方法模拟多场耦合作用下硅纳米颗粒（50nm以下）形成过程，揭示高产率、高尺寸集中度硅纳米颗粒的脉冲放电制备机理，掌握半导体脉冲放电电源设计、专用工作液、工艺参数优化等关键技术；开展高性能纳米硅浆料技术基础研究，将基于兆赫超声技术的液体压力激波和基于空间位阻效应的嵌段共聚物模板方法结合起来，实现硅纳米颗粒的稳定长效分散；研究基于纳米硅浆料的局域硼背场技术，采用背面钝化和局域接触方法，优化参数设计和烧结工艺，抑制界面缺陷形成，降低背面复合速率，提高光谱响应，解决高效背场和背钝化技术的低成本应用难题。项目研究对促进我国光伏技术实现从重点跟踪到突出跨越的战略转变，具有重要的理论研究意义和工程应用前景。

针对效率20%以上晶硅太阳能电池的低成本制造技术瓶颈，提出一种以重掺硼单晶硅为原料、多场耦合脉冲放电制备硅纳米颗粒的新方法，替代液（或气态）硼源制作无高温热损伤、工艺成本低的局域硼背场。采用分子动力学方法模拟多场耦合作用下硅纳米颗粒（50nm以下）形成过程，揭示高产率、高尺寸集中度硅纳米颗粒的脉冲放电制备机理，掌握半导体脉冲放电电源设计、专用工作液、工艺参数优化等关键技术；开展高性能纳米硅浆料技术基础研究，将基于兆赫超声技术的液体压力激波和基于空间位阻效应的嵌段共聚物模板方法结合起来，实现硅纳米颗粒的稳定长效分散；研究基于纳米硅浆料的局域硼背场技术，采用背面钝化和局域接触方法，优化参数设计和烧结工艺，抑制界面缺陷形成，降低背面复合速率，提高光谱响应，解决高效背场和背钝化技术的低成本应用难题。在此基础上，采用硼掺杂硅浆料及激光熔覆工艺制备出一种新型高效的局部硼铝背场结构，并设计出一条SP-PERC高效电池工艺路线。该工艺的特点在于：首先采用硅浆料作为硼源，通过皮秒激光熔覆工艺在获得更小热影响区的同时又实现了硼元素向基体内的高效扩散，与铝浆共同烧结后形成了一种新型高效的局部硼铝背场，提高了p+层中的载流子浓度，降低了背面的复合速率。其次，硅浆料经皮秒激光熔覆后在电池背面形成了晶态的重掺杂硅熔覆层结构，对于促进硅铝合金层形成，降低接触电阻，增加结深，抑制背场孔洞产生等方面都有明显效果。采用硼掺杂硅浆料及激光熔覆工艺制备出一种新型高效的局部硼铝背场结构，并设计出一条SP-PERC高效电池工艺路线。试验结果表明，此工艺方法制备的高效SP-PERC电池背面复合速率降至100cm/s以内，平均效率超过20.3%，效率提升0.3～0.4%，填充因子最高可以提升0.8%。项目研究对促进我国光伏技术实现从重点跟踪到突出跨越的战略转变，具有重要的理论研究意义和工程应用前景。