低成本多孔黑硅材料可控制备及其太阳能电池研究

Low cost and high efficiency are two competing factors in determining the wide applications of the solar cells. This project is based on our previous research works of the metal-assisted electroless etched black silicon. We systematically investigated the evolution of the micro- or nano-structures of black silicon nanowires as the resistivity of the silicon wafer increases. We successfully synthesized both the porous p-type silicon nanowires and porous n-type silicon nanowires via a one-step etching approch.We aim to focus on this novel, facile, easily-cotrolled and high efficiency method,to synthesize the large area and high quality black silicon materials with high absorption rate over a wide range of the solar spectra (from 250nm to 2500nm). We will investigate the effect of etching parameters, dopants concentration, conduction type and oritention on the micro- or nano-structures of the black silicon. We will try to figure out the charge carrier exchange mechanism at the Si/electrolyte interface, silicon dissolution chemistry, band bending and pores formation mechanism. We will focus on the correlation between etching parameters, intrinsic electrical properties of silicon and micro- or nano-structures of the black silicon. We will investigate the possible factors, which can enhance the optical absorption of the black silicon, for example, nanowire length, pores size and pores distribution etc.We will try to understand and to investigate the ways to efficiently separate the photo-generated electron-hole pairs and improve the charge carrier collection efficiency. We will evetually fabricate the low-cost and high-efficiency black silicon solar cells.

高成本工艺及低转换效率是制约太阳能电池大规模应用的两大瓶颈。本项目拟基于申请者多年无电极腐蚀黑硅工作经验，在我们前期实验观察到介孔p型黑硅及介孔n型黑硅微纳结构基础上，尝试基于该种低成本、简单可控、快速高效湿法无电极腐蚀工艺，研制大面积、高质量多孔黑硅材料，制备具有优良广谱吸收特性的介孔黑硅材料，研究不同掺杂浓度、不同导电类型硅材料与含HF电解质溶液接触的界面化学及物理机制，深入分析无电极腐蚀合成黑硅材料中硅/电解质界面载流子交换机制及介孔形成机理，观察腐蚀参数、硅本征电学性能参数与黑硅微观、介观几何结构及形貌之间的相互关系，分析黑硅纳米线阵列高度、线径、介孔尺寸、分布与对应太阳光谱吸收性能间的作用规律，深入探索黑硅电池有效分离及收集光生电子-空穴对的最佳途径，构建低成本、高转换效率的黑硅太阳能电池。

表面陷光结构及性能是晶硅电池进一步提高的关键步骤，目前产业单晶硅电池表面反射率大约是在20-30%，因此有大量光子通过反射浪费了。本项目通过两种方式在晶硅表面光子捕获方面取得了明显进展，第一是采用金属辅助化学腐蚀使晶硅表面反射率降低到1%左右，并通过工艺优化限制了纳米绒面的表面复合，制备出转化效率达到15.5%的黑硅太阳电池；第二是采用飞秒激光微构造手段制备出微纳结构硅表面，反射率可以降低到1%以下，通过化学腐蚀方法在降低表面复合的同时，重构出一种正/倒相间的混合金字塔结构，这种新型减反结构在光子捕获方面优于产业的正金字塔绒面，新型陷光结构电池转化效率较产业绒面高出0.2%。同时采用选择性发射极工艺，制备出的晶硅太阳电池转化效率达到16.1%。