飞秒激光诱导表面毛化提高太阳能电池陷光效率的研究

Femtosecond second laser induced surface-texturing to enhance the efficeincy of solar cells have attracted much attentions from researchers. Compare to traditional method of electrochemical etching, femtosecond laser induced surface-texturing has obvious advantages: the efficiency of enhancement is independent of incident angle and polarization of incident light, the high repeatability and widely application in almost all kinds of materials. Moreover, femtosecond laser assisted etching works in the way of evaporation and gasification, the effect of the melting, liquid flowing and re-solidification of materials are reduced, hence, the surface of the materials is much smoother. Therefore, the femtosecond laser is very suitable for solving problem of surface-texturing in the fabrication of ultra-thin film solar cells. The structures fabricated by femtosecond laser can both enhance the efficiency of solar cells and ensure the quality of the interface of the thin film. This project is intended to design textured structures on Si-based solar cells by femotosecond to improve light-traping efficiency of solar cells, it is also aimed to explore the mechanism of femtosecond laser induced surface-texturing on the surface of semiconducton. The surface-textured semiconductors film will be assembled to solar cells. We are going to study the enhancement of light-trapping efficiency of solar cell with such textured structures. This kind of study will provide guidance in using femtosecond laser in the structure fabrication of film solar cells.

利用飞秒激光诱导表面毛化以提高太阳能电池陷光效率引起了科学家们的广泛关注，相较于传统的电化学刻蚀方法，飞秒激光刻蚀诱导表面毛化具有明显的优势：所诱导的结构在提高效率方面不依赖于光的入射角和偏振态；具有高度的可重复性；适用于加工各种材料（硅、多晶硅、非晶硅和薄膜等）。而且飞秒激光加工时材料的去除主要是以蒸发汽化的方式进行，材料熔化、液相流动以及材料再凝结等过程的影响大大减小，使加工表面更为平整和光滑，因此，飞秒激光非常适合于处理薄膜太阳能电池表面毛化问题，既能提高光捕获效率又要保证薄膜的界面质量。本项目将研究利用飞秒激光诱导表面毛化的方式提高硅基太阳能电池的陷光效率，探索飞秒激光诱导半导体膜材料表面毛化的方法，并利用毛化后的材料组装太阳能电池结构，根据太阳能电池特性测试研究表面毛化结构提高太阳能电池陷光效率的机理。本课题的完成将为飞秒激光在薄膜太阳能电池方面的应用提供新思路。

据多光束干涉的理论，对多光束干涉模拟纳米级阵列图形进行了较全面的探索与总结。通过MATLAB仿真对三光束干涉、四光束干涉、五光束干涉（类型一、类型二）进行了模拟，并讨论了不同波长、不同入射角、不同强度、不同空间分布的光干涉的二维及三维光强分布图，对比了以上类型多光束干涉形成的纳米级周期结构的差异，探索了不同参数改变时对干涉结果影响的规律,结果表明，纳米级阵列图形随着相干光数目、入射角、强度比例以及空间分布变化而变化，因此可根据实际需要灵活选择相干图样。利用共面三束飞秒激光相干制备了M状光栅结构，并研究了预脉冲对光栅结构的影响；多光束相干诱导表面毛化的优势在于：诱导结构的形状可控周期可控，均匀性和有序性好。利用单束飞秒激光制备了大面积均匀有序的自组装条纹结构，周期约700nm，并研究了条纹结构形成的机理，其优势在于条纹结构不受入射角和偏振态的控制，重复性高、制备效率高、均匀性好，适用于加工各种太阳能电池材料。