1、摘 要 高性能多晶硅太阳电池先进生产工艺的研究 专 业：凝聚态物理 摘 要 对于晶体硅太阳电池来说，高效率和低成本一直是研究的两条主线，而多晶硅电池由于成本较低越来越受到青睐。因此，积极发展一些新技术，在提高多晶硅太阳电池转换效率的同时，不增加生产成本或降低成本，对于提高我国太阳电池制备技术和研究水平具有切实的意义。针对当前国内外生产工艺存在较大的差距，本文提出了高性能多晶硅太阳电池先进生产工艺的研究，通过对涂膜掺杂、连续式快速扩散、磷吸杂、湿化学钝化、丝网印刷、烧结等工艺的开发和优化，使得工业生产过程得到简化，同时多晶硅太阳电池的效率得到提高，最后根据实验和理论提出了高效晶体硅太 阳电池的产
2、业化技术路线。 本论文共有七个章节，分别从多晶硅太阳电池制备的各个主要工艺进行论述。 第一章综述了当前晶体硅太阳电池的发展状况，特别是对高效太阳电池的技术研究进行详细的分析，从而引申出发展高性能多晶硅太阳电池的必要性和可行性。 第二章研究旋转涂膜工艺，通过改进涂膜设备和涂膜工艺，使得涂膜均匀性得到较大提高，扩散后方块电阻的标准偏差低于 5。针对连续式快速扩散的生产要求，配制成一种新型的安全、环保、较为廉价的掺杂源，并将原来化学处理所需的十步工艺缩减为四步，节省了大量的工艺时间和工艺成本。 第三章介绍了连续式快速扩散设备和扩散机理，通过对实际扩散温度的精确测量及对比在扩散过程中启用和关闭紫外水银
3、灯对方块电阻的影响，得出快速扩散的真实原因，从而对目前普遍接受的高能光子增强扩散学说表示怀疑。 第四章首先分析了各种掺杂溶液对发射区方块电阻、 p-n 结以及太阳电池性能的影 - i - 响，然后重点研究扩散温度和扩散时间与发射区方块电阻及 p-n 结结深的关系，推导出方块电阻与扩散时间和扩散温度的理论公式。针对工业生产普遍采用的丝网印刷电极方式，研究了快速扩散所需的最佳方块电阻大小，并在这个最佳方块电阻的范围内，改变扩散温度和扩散时间的组合，得出最佳的扩散条件，制备出高质量的 p-n 结，有效提高多晶硅电池的效率。 第五章研究吸杂与钝化工艺。通过磷吸杂效应，多晶硅片的少子寿命在高温扩散过程中
4、不但没有降低，反而得到大幅度提高。在常规的 PECVD 沉积氮化硅薄膜工艺之前，增加了湿化学钝化技术，研究了湿化学钝化时间、钝化温度对多晶硅太阳电池开路电压和效 率的影响。 第六章对丝网印刷电极和烧结工艺进行优化。为了降低串联电阻和提高填充因子，尝试结合丝网印刷和电镀法制备正面电极。对于烧结工艺，首先对烧结温度进行精确的标定，随后研究不同的烧结温度对多晶硅太阳电池性能的影响，优化出最佳的烧结工艺。另外，特别介绍了一种可以直接显示太阳电池旁路结的设备，并用它来检验电池制备过程中可能产生各种旁路结的问题。 通过对以上一些生产工艺的改进，制备的多晶体硅太阳电池取得了良好的结果： 5寸多晶硅光面电池最
5、高效率可达到 15.8%，平均效率约为 15.6； 6 寸多晶硅光面电池 最高效率达到 15.5%，平均效率约为 15.3。这些先进工艺的研究为制备高性能多晶硅太阳电池探索出一条可行路线。 最后根据初期的钝化与激光试验结果，提出开发适合于工业化生产的更高效率电池的设想，即在保留丝网印刷制备电极工艺的前提下，利用双面钝化和激光扫描技术制备高效晶体硅太阳电池。 关键词： 多晶硅太阳电池，高性能，连续式快速扩散，吸杂，钝化 - ii - Abstract ABSTRACT High-efficiency and low-cost are always the two crucial research
6、 goals for the silicon solar cells. Due to the relative cheaper material, the multicrystalline (mc) silicon solar cells have already become the main products in all kinds of solar cells. Thus, it is attractive for the domestic manufacturer to use this low-cost material to fabricate high-efficiency s
7、olar cells. According to the large distance between our industrytechnology and the overseas, this thesis presents the research on the advanced process technologies for cost-effective fabrication of high efficiency mc silicon solar cells. Through investigating the spin-on coating technology, in-line
8、rapid thermal processes, impurity gettering, chemical passivation, screen printing and sintering technologies, the fabrication processes of the mc silicon solar cells have been optimized and simplified, at the same time the efficiency of the cells have been increased. At last the new process technol
9、ogies for making high-efficiency silicon solar cells which is adapt to industrialization have been designed. This thesis includes seven chapters, each chapter focusing on one main technology process of the mc silicon solar cells. In chapter 1 the developments of silicon solar cells are reviewed, som
10、e new technologies about the high-efficiency silicon solar cells are investigated emphatically. From these, its urgent and possible to develop the high performance mc silicon solar cells with cost-effective process. In chapter 2 spin-on coating technology is improved through the optimization of the-
11、 iii - equipment and the process parameters. The film coated on the wafer is very homogeneous, after the diffusion the deviation of the sheet resistance is below 5%. With the requirement of in-line rapid diffusion thermal process, the new, economical, environment-friendly dopant source is mixed, whi
12、ch can simplify the wet-chemical process from ten steps to four steps. So, the process time and materials cost will be saved drastically. In chapter 3 the novel in-line rapid thermal diffusion equipment and the rapid diffusion mechanism are introduced. By calibrating the actual diffusion temperature
13、 carefully and comparing the difference of the sheet resistances between the two kinds of emitters which diffused with and without the UV mercury lamp, the real reasons about the mechanism of rapid diffusion are verified, so the prevalent-accepted theory which means the high energy photons can enhan
14、ce the diffusion process is doubted. In chapter 4 the systematic study about the in-line rapid thermal diffusion for the cost-effective mc silicon solar cells is presented. At first, the influences of different P dopant sources on emitter sheet resistance, p-n junction and solar cells performance ar
15、e investigated. Secondly, through the detailed research about the advanced in-line rapid thermal diffusion process, the emitter sheet resistance Rsheet as a function of diffusion temperature Td and diffusion time td are deduced. Adapted to the screen printing process, the optimum sheet resistance is
16、 concluded by studying the relationship between the sheet resistance and the solar cells performance. Then, in the range of this optimum sheet resistance, the diffusion temperature and diffusion time are adjusted optimally for getting higher efficiency. In chapter 5 gettering and passiation are inve
17、stigated. After the high temperature process, the minority carrier lifetime of the mc silicon wafer is not decreased, but increased to a large scale thanks to the good effect from phosphorous gettering. Chemical passivation process is added before the conventional nitride silicon film deposited by P
18、ECVD. The influences of chemical passivation time and passivation temperature on the open circuit voltage and efficiency of mc silicon solar cell are studied. In chapter 6 the technologies of screen printing and sintering process are optimized. Combined with the screen printing process, the plating
19、technology is developed to decrease the serials resistance and increase the fill factor. For the sintering process, firstly the exact temperature is calibrated, and then the wafers are fired under the different temperature in order to get the highest efficiency. Additionally, the special measurement
20、 is introduced to - iv - Abstract imagine the shunts of the solar cells which will be exsisted during the manufacture process. Through developing and optimizing these advanced technologies mentioned above, the high performance mc silicon solar cells have been made. For 5-inche planar Mc silicon sola
21、r cells, the highest efficiency is up to 15.8%, the average efficiency is more than 15.6%. For 6-inche planar Mc silicon solar cells, the highest efficiency is up to 15.5%, the average efficiency is about 15.3%. These good results allow drawing a conclusion that these advanced technologies can be us
22、ed to improve our industrial manufacture processes. In the last chapter, based on the primary experiment results from passivation and laser-fired contact technologies, the new imagine of fabricating higher efficiency silicon solar cells for the industrialisation has been presented. Its mainly utiliz
23、ed double-side passivation and laser to make high-efficiency silicon solar cells, but on the premise of keeping the screen printing process. Key words: multi-crystalline silicon solar cells, high performance, in-line rapid thermal diffusion, gettering, passivation - v - - vi - 目 录 目 录 第一章 绪论 1 1.1 晶
24、体硅太阳电池理论学术背景 1 1.2 研究意义 4 1.3 国内外太阳电池发展现状 5 1.3.1 多晶硅太阳电池的产业化发展 5 1.3.2 高效晶体硅太阳电池的研究启示 8 1.4 课题来源 18 1.5 研究的线索与思路 18 1.6 主要研究内容 19 第二章 涂膜掺杂 22 2.1 旋转涂膜法 22 2.2 旋转涂膜工艺的改进 23 2.3 新型掺杂溶液及化学处理工艺的简化 26 2.4 批量掺杂的设想 29 第 3 章 连续式快速扩散 31 3.1 快速扩散研究成果的回顾与分析 31 3.2 连续式快速扩散设备的设计 34 3.3 连续式快速扩散特点 37 3.4 连续式快速扩散方
25、法 40 3.5 扩散温度的校正 43 3.6 快速扩散的机理研究 对高能光子增强扩散效应的疑问 45 第 4 章 快速扩散制备多晶硅太阳电池的研究 49 4.1 掺杂溶液的选择 49 4.1.1 掺杂溶液对方块电阻的影响 50 - vii - 中山大学学位论文 4.1.2 掺杂溶液对磷原子分布的影响 52 4.1.3 掺杂溶液对多晶硅太阳电池性能的影响 53 4.2 扩散温度和扩散时间对方块电阻、 P N 结的影响 55 4.2.1 在一定的扩散温度下，方块电阻与扩散时间的关系 56 4.2.2 在一定的扩散时间下，方块电阻与扩散温度的关系 59 4.2.3 扩散温度和扩散时间对磷原子分布的
26、影响 64 4.3 针对丝网印刷电极方式，方块电阻的最优化 68 4.3.1 在不同的扩散条件下，方块电阻对多晶硅太阳电池性能的影响 69 4.3.2 在相同的温度下，改变扩散时间得到的不同方块电阻对多晶硅太阳电池性能影响 74 4.3.3 不同方块电阻对内量子效率的影响 77 4.4 在最佳方块电阻前提下不同的扩散条件所对多晶硅太阳电池性能的影响 78 4.4.1 扩散条件的确定 79 4.4.2 不同扩散条件下磷原子分布 81 4.4.3 不同扩散条件和扩散方式对多晶硅太阳电池性能的影响 83 第五章 磷吸杂和表面钝化 89 5 1 磷吸杂 89 5.1.1 吸杂理论 90 5.1.2 不
27、同扩散温度下磷吸杂对少子寿命的影响 91 5.1.3 不同扩散时间下磷吸杂对少子寿命的影响 95 5 2 表面钝化 98 5.2.1 表面复合机理 99 5.2.2 PECVD 钝化 100 5.2.3 湿化学钝化 102 第六章 丝网印刷与烧结 111 6.1 丝网印刷 111 6.1.1 正面电极设计 111 6.1.2 丝网印刷与电镀技术结合 114 6.2 烧结工艺的优化 115 6.2.1 烧结温度的标定 116 - viii - 目 录 6.2.2 不同烧结温度对太阳电池性能的影响 118 6.2.3 烧结后旁路结的测试与分析 122 6.3 在最优工艺下制备的多晶硅太阳电池 127 第七章 双面钝化和激光扫描制备高效多晶硅太阳电池的产业化技术 135 7 1 激光快速烧融技术 135 7 2 丝网印刷的背面铝电极采用激光烧融技术的尝试 136 7 3 双面钝化和激光扫描制备高效多晶硅太阳电池的产业化技术设想 140 结语 143 参考文献 146 攻读学位期间发表论文情况 156 致 谢 157 - ix - 中山大学学位论文 - x -
