太阳电池用多晶硅锭红外检测中阴影的表征分析

Analysis of Shadows in Multicrystalline Silicon Ingots for Solar Cells Characterized by Infrared Detectors

研究了多晶硅铸锭过程中,硅锭内部红外探伤测试中显示黑斑位置晶体缺陷的杂质组成,并根据杂质成分推导了此种缺陷的形成机理和条件。采用光致发光(PL)技术、扫描电子显微镜(SEM)和X射线能谱仪(EDS)对杂质进行了表征与分析。结果显示,形成阴影的夹杂在晶界中存在的形态主要为针状或薄片状,其组成成分主要为C,N和Si元素。而Si_3N_4的出现可能有两个原因:一是Si_3N_4涂层脱落而沉积在晶界中;二是溶解在液相中的N局部过饱和。此外,结晶过程中,SiC也随之成核并生长,在晶界上形成夹杂物,同时伴随着微缺陷的增加。据此提出了去除多晶硅锭内部阴影的几点措施。

The impurity composition of the crystal defects in the multicrystalline silicon ingots which were displayed as black shadows in infrared detection test during the casting process was investigated.The formation mechanism and conditions of the defects were deduced according to the impurity composition. The photoluminescence（ PL） technique,scanning electron microscope（ SEM） and X-ray energy dispersive spectrometer（ EDS） were used to characterize and analyze the impurities. The results show that the formation of the inclusions which were displayed as shadows in infrared detection are mostly acicular or flaky in the grain boundaries and are mainly composed of carbon,nitrogen and silicon element. Two reasons may be responsible for the appearance of the Si_3N_4. Firstly,Si_3N_4 coatings came off and were deposited in the grain boundaries. Secondly,the dissolved nitrogen supersaturated locally. Besides,Si C might nucleate,grow and turn to be inclusions on the grain boundaries in the process of crystallization along with the increase of the microdefects. Some measures were presented to eliminate the shadows in multicrystalline silicon ingots according to the results.